Different biliary excretion systems for glucuronide and sulfate of a model compound; study using Eisai hyperbilirubinemic rats.

Abstract

The disposition of conjugated metabolites (sulfate and glucuronide) was investigated in Eisai hyperbilirubinemic rats (EHBR) and normal Sprague-Dawley (SD) rats by in vivo and liver perfusion methods. EHBR are mutant rats that have conjugated hyperbilirubinemia as an autosomal recessive trait inheritance, and they show impaired excretion of organic anions into the bile. 6-Hydroxy-5,7-dimethyl-2-methylamino-4-(3-pyridylmethyl) benzothiazole (E3040), a novel dual inhibitor of 5-lipoxygenase and thromboxane A2 synthetase, was used as a model compound, because the major metabolites of E3040 are glucuronide and sulfate. After the i.v. injection of [14C]E3040 to EHBR and SD rats, the plasma AUC for glucuronide was greater in EHBR than in SD rats. The cumulative biliary excretion of the glucuronide was impaired to a great extent in EHBR, and the urinary excretion was enhanced. There was no significant difference in the cumulative biliary and urinary excretion of sulfate between EHBR and SD rats. The influx, efflux and sequestration rates of E3040, measured by a multiple indicator dilution method in the perfused rat liver, were similar in EHBR and SD rats. The biliary excretion of the glucuronide formed in the liver, measured by the liver perfusion method, was also severely impaired in EHBR, so the recovery of the glucuronide in the outflow specimens was markedly enhanced. The disposition of the sulfate did not change in either type of rat.(ABSTRACT TRUNCATED AT 250 WORDS)