Organic anion transport in rabbit renal basolateral membrane vesicles

Pathways for p-aminohippurate (PAH) transport across the basolateral membrane of rabbit proximal tubule cells were investigated from studies of [3H] PAH uptake in membrane vesicles isolated by Percoll-density gradient centrifugation. The 10-s uptake of PAH was not significantly different when measured in the absence of cation gradients or in the presence of inwardly directed Na, Li, K or choline gradients that suggests the absence of a mechanism mediating Na-PAH cotransport. A probenicid-sensitive, trans-stimulation of [3H] PAH uptake was observed in the presence of an outward PAH gradient. PAH gradient-driven [3H] PAH uptake was cis-inhibited by glutarate, alpha-ketoglutarate, adipate and sebacate and outward gradients of alpha-ketoglutarate trans-stimulated probenicid-sensitive PAH uptake. A concentrative accumulation of PAH was measured in the presence of an inward Na gradient and the dicarboxylates glutarate or alpha-ketoglutarate. Compared to the absence of a pH gradient, an inside alkaline pH gradient induced an increased PAH uptake both in the presence and absence of CO2/HCO3. Inside-negative and inside-positive voltage differences were observed to stimulate and inhibit alpha-ketoglutarate gradient-driven PAH uptake, respectively. alpha-Ketoglutarate gradient-driven PAH uptake was progressively reduced in the presence of increasing penicillin concentration and an outward gradient of alpha-ketoglutarate induced an increased level of [14C] penicillin uptake. These results suggest the presence of a probenicid-sensitive organic anion exchange mechanism as a pathway for PAH and penicillin transport across the basolateral membrane of rabbit proximal tubule cells.(ABSTRACT TRUNCATED AT 250 WORDS)