Effects of Organic Anions and Bile Acid Conjugates on Biliary Excretion of LTC4 in the Rat

Biliary organic anion excretion is mediated by an ATP-dependent primary active transporter, so-called canalicular multispecific organic anion transporter (cMOAT). On the other hand, a multiplicity of canalicular organic anion transport has been suggested. Therefore, to examine the substrate specificity of cMOAT using inhibition of excretion of [³H] LTC₄-derived radioactive products in the bile as a marker, we examined the effects of various organic anions and bile acid conjugates on the biliary excretion of LTC₄ in rats. Biliary excretion of the metabolites of [³H] LTC₄, which was injected via the femoral vein, was markedly inhibited by sulfobromophthalein-glutathione, taurolithocholate-3-sulfate, and ursodeoxycholate-3-O-glucuronide. In contrast, dibromosulfophthalein and cefpiramide slightly inhibited, and pravastatin, taurocholate, and 3,7-sul-UDC did not affect biliary LTC₄ excretion. Furthermore, vinblastine and phenothiazine, a P-glycoprotein substrate and inducer, did not affect biliary LTC₄ excretion. Among various organic anions and bile acid conjugates, LTC₄, sulfobromophthalein-glutathione, taurolithocholate-3-sulfate, and ursodeoxycholate-3-O-glucuronide may be good substrates for cMOAT.