Displacement Characteristics of Intracellularly Accumulated p-Aminohippurate in a Mammalian Renal Transport System in Vitro

¹ From the Department of Zoology, Dartmouth College, Hanover, New Hampshire

Studies on the displacement of actively transported organic acids, subsequent to their intracellular accumulation by thin slices of rabbit renal cortex, indicate the existence of a carrier or trapping mechanism. Displacement of accumulated PAH from carrier is facilitated by the simultaneous presence of transfer competitors. Those competitors which are least actively transported are generally the most effective in causing run-out out of the more actively transported members of the series. Competitive displacement of PAH does not occur in the cold. 2, 4-Dinitrophenol, while very effective in causing run-out of PAH at room temperature, is without such effect in the cold. Metabolic intermediates such as acetate and pyruvate which stimulate the initial uptake of PAH inhibit the loss of intracellularly accumulated PAH. Others such as succinate and -ketoglutarate which inhibit uptake of PAH facilitate its run-out. None of these metabolites affects the competitive displacement of PAH at 0°C.