Effect of vanadate on the renal accumulation of p-aminohippurate in the rabbit kidney tubules in vitro

Abstract

The possible involvement of Na +-K +-ATPase on renal organic anion transport systems was investigated by examining the effect of vanadate and ouabain on the uptake of p-aminohippurate (PAH) by rabbit kidney cortical slices. Addition of increasing concentration of vanadate (0.01–0.1 mM) reduced Na +-K + transport and renal steady-state aerobic accumulation of PAH to 80–50 per cent of the control value, without any significant decrease in tissue concentration of ATP. The rapid Na +-independent component of PAH transport was unaffected by the presence of vanadate (0.1 mM) or ouabain (0.2 mM), whereas the slowly equilibrating component, which makes the largest contribution to the final accumulation of PAH was ca. 50 per cent inhibited, by vanadate and almost abolished by ouabain. The anaerobic uptake of PAH was unaffected by a high concentration of vanadate (1 mM), suggesting that vanadate does not competitively inhibit the transport of organic anions. On the basis of the above-mentioned findings, it is suggested that PAH transport is probably linked in a direct manner to the function of Na +-K +-ATPase.