Physiological toxicokinetic model of perchlorate in rats and its construction method

Abstract

The present invention relates to a method for constructing a physiological toxicokinetic model of rat perchlorate, belongs to the field of food safety and environmental science, and specifically relates to a health risk assessment of animals or people exposed to perchlorate. The present invention discloses a method for constructing a physiological toxicokinetic model of rat perchlorate, comprising the following steps: determining the kinetic process of absorption, distribution, metabolism and excretion of perchlorate in rats; establishing a physiological toxicokinetic model of perchlorate in rats and a chamber composition structure; establishing a differential equation of perchlorate content in rats; collecting model parameters: rat physiological parameters, perchlorate biochemical parameters and perchlorate toxicokinetic parameters; simulating a rat perchlorate physiological toxicokinetic model and optimizing parameters; and establishing a perchlorate daily exposure response relationship model.

Description

Technical Field

[0001] The invention relates to a method for constructing a physiological toxicokinetic model of rat perchlorate, belongs to the field of food safety and environmental science, and specifically relates to health risk assessment of animals or people exposed to perchlorate. Background Art

[0002] Perchlorate is composed of perchlorate ions (ClO 4 - ) and sodium, potassium, ammonium or other cations to form salts, which are widely used as oxidants, fuels or industrial additives in the military, aerospace, fireworks, coatings, fertilizers and medical industries and manufacturing industries. Perchlorate has a highly symmetrical ionic structure, stable physical and chemical properties, strong water solubility and is difficult to degrade. Therefore, most of the perchlorate in the environment eventually migrates through surface water and groundwater, and exists stably in soil and water for a long time. At the same time, perchlorate can be enriched in animals and plants, so that it eventually enters the human body through the food chain and other pathways. In 1997, the U.S. Environmental Protection Agency (EPA) improved the detection limit of perchlorate through the study of ion chromatography conductivity suppression, and discovered perchlorate in the environment for the first time. Perchlorate was included in its pollutant candidate list (CCL) three times in 1998, 2005 and 2009. Perchlorate is extremely widely distributed in nature. Unlike the previous detection of perchlorate pollution based on environmental protection considerations, due to its easy migration and enrichment to the food chain, more and more studies are now being conducted on perchlorate pollution in food. The latest exposure levels of perchlorate in food obtained by the European Food Safety Authority (EFSA) through 18,217 food samples collected between 2013 and 2016 showed that the intake of vegetables and vegetable products, milk and milk products, and fruits and fruit products are important factors causing the exposure of all populations to perchlorate (EFSA, 2017).

[0003] The accumulation of perchlorate in organisms can affect their metabolism, reproduction and development, causing direct harm and potential risks to the health of organisms. A large number of studies have shown that perchlorate mainly has thyroid toxicity, reproductive toxicity and neurotoxicity. Perchlorate is a thyroid hormone disruptor. Its ion radius and charge are similar to those of iodine ions. Its affinity for the sodium-iodine symporter (NIS) of thyroid epithelial cells is about 30 times that of iodine ions. It can compete with iodine ions to bind to NIS, affecting the active transport of iodine ions to thyroid follicular cells, interfering with the synthesis and secretion of thyroid hormones T3 and T4, thereby leading to hypothyroidism and metabolic and nervous system problems, especially posing a greater threat to the health of pregnant women and infants. Because iodine plays an important role in the cognitive development of newborns in the early stages of development, infants with insufficient iodine intake are more likely to suffer from cognitive impairment. At the same time, exposure to perchlorate can also affect the reproduction of organisms and have adverse effects on offspring, mainly manifested in reduced reproductive capacity, reduced number of germ cells, abnormal development, and teratogenicity, death, and poor development of embryos.

[0004] Studies in recent years have shown that all kinds of food are generally contaminated by perchlorate worldwide, but only a few countries and regions such as the United States and the European Union have established limit standards for perchlorate pollution. In 2005, the EPA set the dietary reference dose (RfD) for perchlorate exposure in food and water at 0.7μg / kg bw / day. In April 2015, in Commission Recommendation (EU) 2015 / 682, the European Union issued a monitoring program for perchlorate in food, recommending that each member state monitor perchlorate in its own fruits, vegetables and related processed products and infant foods and other special population foods, and determine the tolerable daily intake (TDI) as 0.3μg / kg bw / day per kilogram of body weight. Although perchlorate pollution in my country is very serious, there is still a lack of national research, and due to industrial differences in my country, perchlorate exposure has a strong regional characteristic, and it is impossible to directly refer to the contribution rate of different perchlorate exposure pathways abroad. At the same time, my country's research on perchlorate is not in-depth enough, and there is currently no standard method for determining perchlorate and related food safety limit standards.

[0005] For risk assessment studies of perchlorate, existing studies mainly adopt an external exposure assessment method, that is, to investigate the dietary perchlorate intake level by measuring the perchlorate content in various foods and the consumption of the food, but this assessment method cannot accurately reflect the actual exposure level of perchlorate entering the human body. In order to accurately assess the exposure risk of dietary perchlorate to the human body, an in vivo exposure assessment method must be adopted. Since perchlorate is almost not metabolized in the body and is excreted through the protozoa, its risk can be assessed by measuring the perchlorate ions in human biological samples. Compared with external exposure to dietary perchlorate, studies based on internal exposure levels of protozoa in biological samples can more accurately assess the daily intake of perchlorate and provide a more reliable basis for epidemiological studies.

[0006] The traditional toxicokinetic model is based on the experimental determination of external exposure doses and the effect doses in biological samples that can be sampled and tested, and uses mathematical methods to study the dynamic changes in the absorption, distribution, metabolism and excretion of foreign compounds or their metabolites in the body over time and their quantitative laws. However, this method is a static mathematical description under multiple constraints and cannot meet the requirements for accurately predicting the exposure dose in the body under actual exposure conditions. In response to the shortcomings of the traditional toxicokinetic model, foreign scholar Teorell first proposed the use of the physiologically based toxicokinetic (PBTK) model in 1937 to simulate the exposure dose and biomarkers of pollutants in the environment. This model uses the principles of physiology and anatomy to connect the entire body in series through blood transport, reflecting the target compound flowing into various organs and tissues with the blood, and simulating the metabolism, transformation and excretion of the compound in the body. Compared with the traditional single-component toxicokinetic model, the PBTK model can systematically reflect the time and tissue and organ metabolic distribution characteristics of pollutants in the body, greatly integrate the physiological and biochemical differences of different experimental subjects, and can extrapolate the exposure pathways, exposure doses and exposure subjects, thereby promoting the toxicological knowledge learned from experimental animals to the public health field and achieving accurate assessment of population health risks.

[0007] As an important application of the pharmacokinetic principle in toxicology research, the PBTK model is widely used to simulate the in vivo biological monitoring indicators of chemical pollutants in the environment and food, and to associate internal and external exposure doses. In recent years, the application research of the PBTK model has gradually emerged at home and abroad, such as the PBTK model of pesticide chlorpyrifos residues in the environment, heavy metals lead, copper, and zinc. However, the perchlorate PBTK models established at home and abroad mostly use intravenous single-dose radiolabeled perchlorate and iodide ions as co-interventions, and aim to study its toxic effects on the thyroid gland. Most studies only establish metabolic kinetic models for a single chamber, urine, and have not established an internal and external exposure association mechanism. Summary of the invention

[0008] The technical problem to be solved by the present invention is to provide a physiological toxicokinetic model of rat perchlorate and a construction method thereof.

[0009] In order to solve the above technical problems, the present invention provides a method for constructing a physiological toxicokinetic model of perchlorate in rats, comprising the following steps:

[0010] 1) To determine the kinetics of perchlorate absorption, distribution, metabolism, and excretion in rats;

[0011] 2) Establish the physiological toxicokinetics model and compartmental structure of perchlorate in rats;

[0012] 3) Establish a differential equation for perchlorate content in rats;

[0013] 4) Collect model parameters: rat physiological parameters, perchlorate biochemical parameters, and perchlorate toxicokinetic parameters;

[0014] 5) Simulation and parameter optimization of physiological toxicokinetic model of perchlorate in rats;

[0015] 6) A perchlorate daily exposure-response relationship model was established.

[0016] As an improvement of the method for constructing the physiological toxicokinetic model of rat perchlorate of the present invention:

[0017] Preferably, in 1), the kinetic process of absorption, distribution, metabolism and excretion of perchlorate in rats is determined by literature search and data analysis. Specifically, the kinetic process includes: the first step, absorption. There are many ways for perchlorate to be absorbed by the human body, including absorption by the digestive system, respiratory system, and skin, among which absorption by the digestive tract is the most important exposure mode. The second step, distribution. After perchlorate enters the human body, it is widely distributed in various tissues in the body, with the thyroid gland as the target organ. The third step, metabolism. Perchlorate does not undergo redox or binding in the body and has almost no metabolism. The fourth step, excretion. Perchlorate is cleared quickly in the human body, mainly excreted in the urine as unmetabolized precursors.

[0018] Preferably, the compartment structure of the rat physiological toxicokinetics model of perchlorate includes thyroid gland, kidney, liver, fat, stomach, intestine, skin, lung, other tissues and blood circulation system, and each compartment is connected together through the blood circulation system, i.e., arterial blood and venous blood.

[0019] Note: Other tissues represent tissues and organs not involved in the model structure, such as brain, heart, spleen, muscle, etc.

[0020] Preferably, the experimental data of the research group of the present invention and the perchlorate model collected in the existing literature are combined to list the corresponding mathematical differential equations for each tissue organ chamber and construct the model using computer software.

[0021] Preferably, the present invention selects urine, blood and thyroid as important research sites, constructs a PBTK model based on site differential equations using the physiological and biochemical model parameters of perchlorate, and verifies the correlation between the theoretical model and the actual value. The change in the content of perchlorate in the chamber is described by the mass conservation differential equation, that is: the change in the substance per unit time in the chamber = the instantaneous mass of the substance flowing into the chamber with arterial blood - the instantaneous mass of the substance flowing out of the chamber with venous blood + the generation term of the substance in the chamber - the elimination term of the substance in the chamber;

[0022] Change rate of total perchlorate in urine (mg / h):

[0023]

[0024] in:

[0025] —Rate of change of total perchlorate in urine (mg / h);

[0026] k U — elimination rate constant of perchlorate in urine (1 / h);

[0027] —renal blood perchlorate concentration (mg / mL);

[0028] V K —Kidney volume (mL).

[0029] Rate of change of total perchlorate in thyroid gland (mg / h):

[0030]

[0031]

[0032]

[0033] in:

[0034] —The rate of change of the total amount of perchlorate in thyroid blood, thyroid follicles, and thyroid cavity, respectively (mg / h);

[0035] Q T ×(C AR -C TS )—Blood flow into the thyroid gland*Concentration difference between arterial blood and venous blood;

[0036] — Diffusion restriction models from follicle to blood and from cavity to follicle, respectively; — Michaelis-Menten equations from thyroid blood to thyroid follicles and from thyroid follicles to thyroid cavity, respectively;

[0037] Changes in perchlorate levels in venous blood (mg / h):

[0038]

[0039] in:

[0040] —Changes in perchlorate levels in venous blood (mg / h);

[0041] - The rate of change of perchlorate content entering the blood circulation system through the liver, stomach and intestines (mg / h); and so on, Respectively represent the rate of change of perchlorate content entering the blood circulation system through the skin, fat, other tissues, thyroid gland, and kidney (mg / h);

[0042] Q LU ×C VE - the rate at which perchlorate enters the arterial blood through the pulmonary circulation and is exported to various chambers (mg / h);

[0043] — Diffusion-limited model from red blood cells to free plasma;

[0044] — Michaelis-Menten equation for the rate of change of perchlorate binding in plasma;

[0045] k B ×A binding — Clearance rate of perchlorate bound to plasma.

[0046] Preferably, the experimental data of the research group itself is combined with the biochemical parameters of the perchlorate model and the tissue / blood distribution coefficient collected in existing literature, and the corresponding mathematical differential equations are listed for each tissue organ compartment and the model is constructed using computer software.

[0047] Preferably, based on the urine, blood and thyroid data of rats subjected to single oral administration of high and low doses of perchlorate, the model parameters are adjusted so that the content-time curve simulated by the model is as close as possible to the experimental data. That is, based on the animal experimental data, the SimBiology tool (v6.10) of Matlab software (R2021a) is used to adjust the model parameters of each chamber so that the obtained metabolite content-time curve is as close as possible to the experimental data.

[0048] Preferably, based on the constructed perchlorate PBTK model, the present invention can correctly deduce the actual exposure values ​​of internal organs in the body by detecting the perchlorate level in urine, and can deduce the actual exposure values ​​in vitro through the correlation model, which can more clearly describe the metabolic kinetics of perchlorate from the perspective of physiological structure.

[0049] Preferably, a PBTK-based perchlorate internal and external exposure correlation model is obtained by curve fitting the perchlorate PBTK model parameters in urine and blood with the corresponding oral gavage dose.

[0050] The present invention also provides a physiological toxicokinetic model of rat perchlorate constructed by any of the above methods.

[0051] The model has a very broad development prospect in the field of food safety, and may even gradually replace animal experiments and become an important means of studying the ecotoxicology of pollutants.

[0052] Based on the metabolic pathway of perchlorate in the body, the present invention uses urine, blood, and thyroid as important research sites, and uses the parameters of the physiological and biochemical model of perchlorate to construct a PBTK model based on site differential equations. At the same time, the high and low dose model stability values ​​are deduced, and a correlation model is constructed to simulate the daily external exposure of perchlorate and the stability value level of the metabolite, providing an analytical means for accurately evaluating the actual external exposure of the human body.

[0053] The physiological toxicokinetics model of rat perchlorate established by the present invention simulates external exposure to SD rats with high and low doses of single intragastric perchlorate gavage, and establishes a complete in vivo perchlorate distribution and metabolism model. On the other hand, this model takes into account the characteristics of blood perfusion, membrane permeability, and tissue affinity for perchlorate to group tissues and organs, and determines a multi-chamber model. According to the metabolic characteristics of perchlorate, the metabolic kinetic process of perchlorate is constructed with perchlorate protomers as indicators. And according to the perchlorate PBTK model parameters in urine, blood and thyroid gland and the corresponding intragastric dose, a PBTK-based perchlorate internal and external exposure correlation model is obtained. The model has broad development prospects in the field of food safety, and may even gradually replace animal experiments and become an important means of pollutant ecotoxicology research.

[0054] In summary, the physiological toxicokinetics model of perchlorate established in the present invention simulates external exposure by single oral gavage of high and low doses, and establishes a daily exposure hazard and dose-response relationship model through internal and external related exposure, making it possible to estimate the in vitro dietary exposure dose based on the level of in vivo monitoring indicators. Since the model has the characteristics of species extrapolation, the parameters of the model can be adjusted according to human physiological parameters, tissue organ distribution coefficients, and metabolic kinetic parameters, and the model extrapolation process from rats to humans can be realized, and finally a human-based physiological toxicokinetics model of perchlorate can be obtained; thereby, the health risks of human exposure to perchlorate can be objectively evaluated, and scientific theoretical support can be provided for the formulation and revision of the daily minimum limit of perchlorate. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The specific implementation modes of the present invention are further described in detail below with reference to the accompanying drawings.

[0056] Figure 1 The present invention is a flow chart of the method for constructing a physiological toxicokinetic model of rat perchlorate;

[0057] Figure 2 The structure diagram of the physiological toxicokinetic model of perchlorate in rats of the present invention;

[0058] Figure 3 The physiological toxicokinetic model of rat perchlorate with original parameters in the embodiment of the present invention simulates the cumulative content-time curve of perchlorate in urine and the measured level diagram;

[0059] Figure 4 The physiological toxicokinetic model of rat perchlorate with original parameters in the embodiment of the present invention simulates the perchlorate content-time curve in plasma and the measured level diagram;

[0060] Figure 5 The physiological toxicokinetic model of rat perchlorate with original parameters in the embodiment of the present invention simulates the perchlorate content-time curve in the thyroid gland and the measured level diagram;

[0061] Figure 6 The model prediction of the total amount of urine excretion under perchlorate dietary exposure in the embodiment of the present invention (taking 72 hours as an example);

[0062] Figure 7 The model prediction of the plasma content under perchlorate dietary exposure in the embodiment of the present invention (taking 72 hours as an example);

[0063] Figure 8 1 is a model of the relationship between dietary perchlorate exposure and blood and urine exposure in the embodiments of the present invention. DETAILED DESCRIPTION

[0064] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0065] Example 1: A method for constructing a physiological toxicokinetic model of perchlorate in rats, comprising the following steps:

[0066] 1) To determine the kinetics of perchlorate absorption, distribution, metabolism, and excretion in rats;

[0067] 2) Establish the physiological toxicokinetics model and compartmental structure of perchlorate in rats;

[0068] 3) Establish a differential equation for perchlorate content in rats;

[0069] 4) Collect model parameters: rat physiological parameters, perchlorate biochemical parameters, and perchlorate toxicokinetic parameters;

[0070] 5) Simulation and parameter optimization of physiological toxicokinetic model of perchlorate in rats;

[0071] 6) A perchlorate daily exposure-response relationship model was established.

[0072] The details are as follows:

[0073] 1. The specific process of constructing the physiological toxicokinetics model of perchlorate in rats is shown in Figure 1 , the steps are as follows: Determine the kinetics of absorption, distribution, metabolism and excretion of perchlorate in rats through literature search and data analysis. Specifically, the kinetic process includes: the first step, absorption. There are many ways for perchlorate to be absorbed by the human body, including absorption by the digestive system, respiratory system, and skin, among which absorption through the digestive tract is the most important exposure method. The second step is distribution. After perchlorate enters the human body, it is widely distributed in various tissues in the body, with the thyroid gland as the target organ. The third step is metabolism. Perchlorate does not undergo redox or binding in the body and has almost no metabolism. The fourth step is excretion. Perchlorate is cleared quickly in the human body, mainly excreted in the urine as unmetabolized precursors.

[0074] 2. Determine the physiological toxicokinetic model of perchlorate in rats

[0075] The physiological toxicokinetics model structure of perchlorate in rats was constructed as follows Figure 2 The model chamber structure includes the thyroid gland, kidneys, liver, fat, stomach, intestines, skin, lungs, other tissues and the blood circulation system. Each chamber is connected together through the blood circulation system, namely arterial blood and venous blood.

[0076] Figure 2 The meanings of the English abbreviations are as follows:

[0077] Tissue blood flow (Q), lung (LU), skin (SK), fat (F), other tissues (O), thyroid (T), liver (L), stomach (ST), intestine (G), kidney (K), hepatic artery (HA).

[0078] Figure 2 The other tissues in the model represent tissues and organs not involved in the model structure, such as brain, heart, spleen, muscle, etc.

[0079] Perchlorate is absorbed in the stomach, flows into the venous blood after passing through the liver, and then enters the arteries through the pulmonary circulation. The arteries are then distributed to various tissues and organs.

[0080] The thyroid gland is the target organ of perchlorate, and the kidney is the organ through which most perchlorate is excreted in the urine. The blood connects various tissues and organs and is a tissue of great concern in toxicological studies and in vivo exposure assessment. Therefore, urine, blood and thyroid gland were selected as important research sites. The other organs mentioned above were modeled as simple perfusion-limited models, and the relevant parameters were calculated using empirical formulas.

[0081] 3. Build mathematical models and write differential equations

[0082] Urine, blood and thyroid gland were selected as important research sites. The PBTK model based on site differential equation was constructed using the parameters of the physiological and biochemical model of perchlorate, and the theoretical model was verified by correlating the actual value. The change of perchlorate content in the chamber is described by the mass conservation differential equation, that is, the change of the substance in the chamber per unit time = the instantaneous mass of the substance flowing into the chamber with arterial blood - the instantaneous mass of the substance flowing out of the chamber with venous blood + the generation term of the substance in the chamber - the elimination term of the substance in the chamber.

[0083] Change rate of total perchlorate in urine (mg / h):

[0084]

[0085] in:

[0086] —Rate of change of total perchlorate in urine (mg / h); dA U / dt represents the derivative of the perchlorate content in urine with respect to time;

[0087] k U —Excretion rate constant of perchlorate in urine (1 / h); k U It is obtained by fitting the experimental data, see Table 2;

[0088] —Perchlorate concentration in kidney blood (mg / mL); C Krepresents the concentration of perchlorate in kidney tissue, P K is the tissue:blood partition coefficient of the kidney.

[0089] V K —Kidney volume (mL).

[0090] Rate of change of total perchlorate in thyroid gland (mg / h):

[0091]

[0092]

[0093]

[0094] in:

[0095] —The rate of change of the total amount of perchlorate in thyroid blood, thyroid follicles, and thyroid cavity, respectively (mg / h);

[0096] Q T ×(C AR -C TS )—Blood flow into the thyroid gland*Concentration difference between arterial blood and venous blood;

[0097] — Diffusion restriction models from follicle to blood and from cavity to follicle, respectively; — Michaelis-Menten equations from thyroid blood to thyroid follicles and from thyroid follicles to thyroid cavity, respectively;

[0098] A is the chemical content (mg), Q is the tissue blood flow (mL), C is the chemical concentration (mg / mL), and P is the tissue:blood partition coefficient. TF ,PA TL is the permeability-area cross product, describing the ClO 4 - Passive diffusion through follicles and lumen. maxTF 、V maxTL , K mTF and K mTL It is ClO 4 - The maximum reaction rate of active transport to the follicle and lumen (mg / h) and the Michaelis-Menten constant (mg / L). The superscript TS represents thyroid blood, TF represents thyroid follicle, and TL represents thyroid lumen.

[0099] Changes in perchlorate levels in venous blood (mg / h):

[0100]

[0101] in:

[0102] —Changes in perchlorate levels in venous blood (mg / h);

[0103] -The rate of change of perchlorate content (mg / h) entering the blood circulation system through the liver, stomach and intestines. Respectively represent the rate of change of perchlorate content entering the blood circulation system through the skin, fat, other tissues, thyroid gland, and kidney (mg / h);

[0104] Q LU ×C VE - the rate at which perchlorate enters the arterial blood through the pulmonary circulation and is exported to various chambers (mg / h);

[0105] — Diffusion-limited model from red blood cells to free plasma;

[0106] — Michaelis-Menten equation for the rate of change of perchlorate binding in plasma;

[0107] k B ×A binding — Clearance rate of perchlorate bound to plasma.

[0108] PA RBC V is the cross product of the red blood cell osmotic area (mL / h). maxB and K mB It is ClO 4 - Maximum reaction rate (mg / h) and Michaelis-Menten constant (mg / L) for binding to plasma proteins. B It is plasma protein-bound ClO 4 - The first dissociation constant (1 / h). Qi represents the volume of other tissues excluding the lung (mL). In the superscript: VE represents venous blood, RBC represents red blood cells, and B represents plasma binding.

[0109] 4. Collect physiological toxicokinetic model parameters of perchlorate in rats

[0110] The model parameters mainly include three categories: rat physiological parameters, perchlorate biochemical parameters and perchlorate toxicokinetic parameters. The relevant physiological parameters of rats in this example are shown in Table 1.

[0111] Table 1 Physiological parameters of the PBTK model in male rats

[0112]

[0113]

[0114] 5. Simulation and optimization of physiological toxicokinetic model of perchlorate in rats

[0115] Based on the differential equation obtained in step 3 and the physiological toxicokinetic model parameters of rat perchlorate collected in step 4, the model parameters are adjusted to make the content-time curve simulated by the model as close as possible to the actual data. Under the original parameter conditions, the physiological toxicokinetic model of rat perchlorate is used to simulate the perchlorate content-time curve in the urine of rats after oral ingestion of 10 mg / kg·bw and 100 mg / kg·bw perchlorate. Then compare the model output results with the actual test values, and adjust the model parameters to make the model simulation curve as close to the test data curve as possible ( Figure 3 , Figure 4 , Figure 5 ). In this example, the parameters of the rat perchlorate physiological toxicokinetic model adjusted according to the experimental data are shown in Table 2.

[0116] Figure 3-5 The model simulation curve is obtained by solving the differential equation listed in step 3 using computer software.

[0117] Rats were gavaged with 10 mg / kg.bw and 100 mg / kg.bw of perchlorate, respectively, with distilled water as control. Urine and feces were collected at 3, 6, 9, 12, 15, 18, 24, 30, 36, 42 and 48 hours after gavage. The same experiment was repeated and the rats were killed at 1, 4, 8, 12, 24, 48 hours to obtain blood and thyroid. The perchlorate content in urine, plasma and thyroid was determined by HPLC-MS / MS method.

[0118] Table 2. Physiological toxicokinetic model parameters of perchlorate in male rats

[0119]

[0120]

[0121] 6. Application of physiological toxicokinetic model of perchlorate in rats

[0122] The present invention simulates the total amount of urine excretion and the relationship between blood content and time under perchlorate dietary exposure based on the physiological toxicokinetic model of rat perchlorate after optimizing parameters ( Figure 6 , Figure 7 ). At the same time, by adjusting the daily exposure dose of perchlorate, the maximum blood concentration and the maximum daily urine excretion after exposure were predicted, and the dose-effect curve of rat perchlorate dietary exposure was established ( Figure 8). The model can predict the level of perchlorate content in rat urine and blood and the time trend based on the external exposure dose of perchlorate. On the one hand, the invention clarifies the daily exposure-response relationship of perchlorate; on the other hand, because the model has the characteristics of species extrapolation, the parameters of the model can be adjusted according to human physiological parameters, tissue organ distribution coefficients, and metabolic kinetic parameters, so as to realize the extrapolation process from rats to humans, and finally obtain a perchlorate physiological toxicokinetic model based on the human population; thereby, the health risks of human exposure to perchlorate can be objectively evaluated, and scientific theoretical support can be provided for the formulation and revision of the daily minimum limit of perchlorate.

[0123] The details are as follows: The rat model established in steps 2-5 was used to simulate the daily repeated exposure to perchlorate, and the daily exposure doses (1, 3, and 10 mg / kg·bw / day) that enter the human body in three meals were used for a 3-day simulation to obtain Figure 6-7 . The dose information in the model input was adjusted to an interval of 8 hours between oral administrations, a daily exposure dose gradient of 0.4 to 100 mg / kg·bw / day, and continued administration for 30 days. The model outputs a series of maximum venous concentrations and maximum daily urine perchlorate levels corresponding to the daily exposure doses, where the maximum venous concentration is the maximum value of the perchlorate concentration in the venous blood during the administration period, and the maximum daily urine perchlorate content is the maximum value of the content excreted through the urine every 24 hours during the administration period. The exposure was linearly fitted based on the obtained maximum venous concentration and maximum daily urine perchlorate content values ​​to obtain the dose-effect curve of rat dietary perchlorate exposure.

[0124] Finally, it should be noted that the above examples are only some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or associated with the content disclosed by a person skilled in the art should be considered as the protection scope of the present invention.

Claims

1. A method for constructing a physiological toxicokinetic model of perchlorate in rats, characterized in that The following steps are involved: 1) Determine the kinetics of perchlorate absorption, distribution, metabolism, and excretion in rats; 2) Establish the physiological toxicokinetics model and compartmental structure of perchlorate in rats; 3) Establish the differential equation of perchlorate content in rats: According to the characteristics of perchlorate metabolism and organ distribution, urine, blood and thyroid gland were selected as important research sites for the establishment of differential equations; the change of perchlorate content in the chamber was described by the mass conservation differential equation, that is, the change of the substance in the chamber per unit time = the instantaneous mass of the substance flowing into the chamber with arterial blood - the instantaneous mass of the substance flowing out of the chamber with venous blood + the generation term of the substance in the chamber - the elimination term of the substance in the chamber; Change rate of total perchlorate in urine (mg / h): in: —Rate of change of total perchlorate in urine (mg / h); k U — elimination rate constant of perchlorate in urine (1 / h); —renal blood perchlorate concentration (mg / mL); V K —kidney volume (mL); Rate of change of total perchlorate in thyroid gland (mg / h): in: —The rate of change of the total amount of perchlorate in thyroid blood, thyroid follicles, and thyroid cavity, respectively (mg / h); Q T ×(C AR -C TS )—Blood flow into the thyroid gland*Concentration difference between arterial blood and venous blood; — Diffusion restriction models from follicle to blood and from cavity to follicle, respectively; — Michaelis-Menten equations from thyroid blood to thyroid follicles and from thyroid follicles to thyroid cavity, respectively; Changes in perchlorate levels in venous blood (mg / h): in: —Changes in perchlorate levels in venous blood (mg / h); - Change rate of perchlorate content entering the blood circulation system through the liver, stomach and intestines (mg / h); Respectively represent the rate of change of perchlorate content entering the blood circulation system through the skin, fat, other tissues, thyroid gland, and kidney (mg / h); Q LU ×C VE - the rate at which perchlorate enters the arterial blood through the pulmonary circulation and is exported to various chambers (mg / h); — Diffusion-limited model from red blood cells to free plasma; — Michaelis-Menten equation for the rate of change of perchlorate binding in plasma; k B ×A binding - clearance rate of perchlorate binding in plasma; 4) Collect model parameters: rat physiological parameters, perchlorate biochemical parameters, and perchlorate toxicokinetic parameters; 5) Simulation and parameter optimization of rat perchlorate physiological toxicokinetic model; 6) Establish a perchlorate daily exposure response relationship model: By fitting the curves of the PBTK model parameters of perchlorate in urine and blood with the corresponding oral doses, a PBTK-based perchlorate internal and external exposure correlation model was obtained.

2. The method for constructing a physiological toxicokinetic model of perchlorate in rats according to claim 1, characterized in that: The model's chamber structure includes the thyroid gland, kidneys, liver, fat, stomach, intestines, skin, lungs, and circulatory system, and each chamber is connected together through the circulatory system.

3. The method for constructing a physiological toxicokinetic model of perchlorate in rats according to claim 2, characterized in that: Based on the animal experimental data, the SimBiology tool of Matlab software was used to adjust the model parameters of each compartment so that the obtained metabolite content-time curve was as close as possible to the experimental data.

4. The method for constructing a physiological toxicokinetic model of perchlorate in rats according to claim 3, characterized in that: By detecting the perchlorate level in urine or blood, the actual exposure values ​​of internal organs can be correctly deduced internally, and the actual exposure values ​​in vitro can be deduced through correlation models, thereby clearly describing the metabolic kinetics of perchlorate from the perspective of physiological structure.

5. A physiological toxicokinetic model of perchlorate in rats constructed by the method according to any one of claims 1 to 4.

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