Abstract

Hepatic microsomal estrone and estradiol glucuronyltransferase activity were examined in nonpregnant female and pregnant rats and rabbits. Pregnancy decreased glucuronyltransferase activity towards both substrates by 30% in rats and rabbits when activity was expressed per mg of microsomal protein. Because of the increased size of the liver in pregnancy in the rat, activity was increased in this species when expressed per whole liver. The size of the liver was not increased in pregnancy in the rabbit, so that activity per whole liver was also decreased in this species. Pretreatment of nonpregnant rats with 3-methylcholanthrene had little effect on estradiol glucuronyltransferase activity and increased estrone glucuronyltransferase activity 35%. Similar pretreatment of pregnant rats, however, increased estradiol glucuronyltransferase activity approximately twofold and estrone glucuronyltransferase activity approximately threefold. Phenobarbital was a much less potent inducer of estrone and estradiol glucuronyltransferase activities but did increase activities to a greater extent in pregnant rats than in nonpregnant female controls.