Effects of gossypol on PAH transport in the rabbit kidney slice

The present work was carried out to investigate if gossypol, a toxic weak organic acid (p K = 7.2) contained in cottonseed, is secreted by the renal proximal tubule through the organic anion transport system in the rabbit. The slice uptake of p-aminohippurate (PAH), a prototypical organic anion, was significantly inhibited (by 30%) only when the medium concentration of gossypol was raised to 10 −4 M. However, gossypol at the latter concentration also induced a 30% inhibition of the slice uptake of tetraethylammonium (TEA), a prototypical organic cation. Moreover, gossypol at 10 −4 M significantly decreased the slice oxygen consumption (⋍30%) and Mg-ATPase (70%) and NaK-ATPase (90%) activities of renal cortical microsomes, while it significantly decreased the intracellular (K +). These results indicate that gossypol inhibits PAH uptake through nonspecific nephrotoxic effects on cell metabolism and NaK-ATPase activity rather than through its specific interaction with the organic anion transport system.