p-Aminohippurate transport in apical and basolateral membranes of the OK kidney epithelial cells.

p-Aminohippurate (PAH) transport in apical and basolateral membranes of OK cells was studied to characterize each membrane process and to determine which process is important for the vectorial transport of PAH across the OK cell monolayers. PAH uptake from the basal side into OK cells was much higher than from the apical side, and was inhibited almost completely by anion transport inhibitors (probenecid and furosemide) and low temperature. On the other hand, PAH efflux from OK cells to the apical side was higher than to the basal side. The efflux across the apical membrane also was inhibited by the transport inhibitors and low temperature. The uptake of PAH across the basolateral membrane was inhibited by dicarboxylates such as alpha-ketoglutarate, and kinetic analysis showed that the inhibition was a mixed-type. These findings suggest that PAH transport in apical and basolateral membranes of OK cells is a specifically mediated process, and both processes contribute to the vectorial transport of PAH across the cell monolayers. PAH/dicarboxylate exchange may be involved in PAH transport in the basolateral membrane of OK cells.