Provided are electrokinetically-altered fluids (e.g., gas-enriched (e.g., oxygen-enriched) electrokinetic fluids) comprising an ionic aqueous solution of charge-stabilized oxygen-containing nanostructures in an amount sufficient to provide, upon contact with a cell, modulation of at least one of cellular membrane potential and cellular membrane conductivity. Particular aspects of the present invention provide compositions and methods suitable for modulation of at least one of cellular membrane potential and cellular membrane conductivity. Additional aspects provide compositions and methods suitable for modulating intracellular signal transduction, including modulation of at least one of membrane structure, membrane potential or membrane conductivity, membrane proteins or receptors, ion channels, and calcium dependant cellular messaging systems, comprising use of the inventive electrokinetically altered solutions to impart electrochemical and/or conformational changes in membranous structures (e.g., membrane proteins, receptors and/or other components) including G-protein coupled receptors (GPCRs), G-proteins, and/or intracellular junctions (e.g., tight junctions, gap junctions, zona adherins and desmasomes).