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 renal p-aminohippurate (PAH) accumulation and Na+-K+ transport was studied in rabbit cortical slices. 2. Cyanide (CN-), 2,4-dinitrophenol (DNP) and fluoride (F-( at low-medium concentrations, giving rise to a slight decline of tissue ATP concentration, caused a reduction o PAH accumulation without significantly affecting intracellular Na+ and K+ concentrations. However, higher levels of the metabolic inhibitors also resulted in considerable inhibition of active Na+-K+ transport. 3. The rate of carrier-mediated PAH uptake was slow under anaerobic conditions, relative to that measured under aerobic conditions in Na+-depleted slices. In the latter case the maximal accumulation achieved was only 1.55 +/- 0.16. 4. The uptake rate of PAH under anaerobic conditions was not inhibited by the absence of Na+ or addition of metabolic inhibitors in the concentrations used under aerobic conditions. 5. It is concluded that although Na+ is required for the attainment of high accumulation ratios of PAH, oxidative metabolism stimulates PAH flux by a Na+-independent mechanism.