Gender difference in the Oatp1-mediated tubular reabsorption of estradiol 17beta-D-glucuronide in rats

The gender difference in the urinary excretion of estradiol-17beta-glucuronide (E(2)-17betaG) was examined in rats. The urinary clearance of E(2)-17betaG was <250 times lower in male than in female rats. No such major gender difference was observed in its biliary excretion or metabolism in kidney homogenate. Both plasma protein binding and inulin clearance were comparable in male and female rats, suggesting that this gender difference cannot be explained by glomerular filtration. The urinary clearance with respect to the plasma unbound E(2)-17betaG in male rats was