Efflux of organic acids from rabbit kidney cortex

Abstract

Slices of rabbit kidney cortex were equilibrated with selected organic anions. Efflux of substrate from the slices was then observed as a function of time under conditions which emphasized diffusion and minimized energy-dependent reactions. Twenty compounds, including hippurates, benzoates, phenolsulfonphthalein dyes, and sulfonamides, were examined. Rates of diffusion of a variety of organic acids from kidney slices were of a single order of magnitude, ranging from 4 to 12 min. It is, therefore, unlikely that diffusion losses can contribute materially to differences in slice to medium concentration ratios for different substrates. No correlation was observed between the efflux of these compounds and their acidic dissociation constants, their participation in active renal transport, or their partition coefficients between organic solvents and water. Since diffusion of organic acids through renal cortical tissue appears to be independent of their partition coefficients, it is suggested that attempts to explain renal excretory phenomena by the application of the principles of nonionic diffusion should be re-evaluated.