An energy‐dependent, sodium‐independent component of active p‐aminohippurate transport in rabbit renal cortex.

1. The relation between the coupling of metabolic energy to renalp‐aminohippurate (PAH) accumulation and Na+‐K+ transport was studiedin rabbit cortical slices. 2. Cyanide (CN‐), 2,4‐dinitrophenol (DNP)and fluoride (F‐( at low‐medium concentrations, giving rise to aslight decline of tissue ATP concentration, caused a reduction o PAHaccumulation without significantly affecting intracellular Na+ and K+concentrations. However, higher levels of the metabolic inhibitorsalso resulted in considerable inhibition of active Na+‐K+transport. 3. The rate of carrier‐mediated PAH uptake was slow underanaerobic conditions, relative to that measured under aerobicconditions in Na+‐depleted slices. In the latter case the maximalaccumulation achieved was only 1.55 +/‐ 0.16. 4. The uptake rate ofPAH under anaerobic conditions was not inhibited by the absence of Na+or addition of metabolic inhibitors in the concentrations used underaerobic conditions. 5. It is concluded that although Na+ is requiredfor the attainment of high accumulation ratios of PAH, oxidativemetabolism stimulates PAH flux by a Na+‐independentmechanism.