Effect of age and sex on the inducibility of hepatic microsomal 4-nitrophenol UDP-glucuronyltransferase activity in rats

Abstract

In this report, we examined the effect of age and sex of Long-Evans rats on the inducibility of 4-nitrophenol glucuronyltransferase activity in liver microsomes of animals treated with phénobarbital, dexamethasone, or 3-methylcholanthrene. Glucuronyltransferase activity in control male liver microsomes was approximately 50–75% higher than that in control female liver microsomes. Treatment with sodium phenobarbital (i.p., 75 mg/kg/day) for 3–4 days increased glucuronyltransferase activity by approximately 100% and 60% in liver microsomes from adult female and male rats, respectively, but did not influence this activity in liver microsomes from immature female and male rats. Treatment with dexamethasone (i.p., 75 mg/kg/day) for 3–4 days increased glucuronyltransferase activity by approximately 4-fold in liver microsomes from immature female rats but markedly decreased this enzyme activity in liver microsomes from adult female rats, adult male rats, and immature male rats. Treatment with 3-methylcholanthrene (i.p., 25 mg/kg/day) for 3–4 days increased glucuronyltransferase activity by approximately 10- to 13-fold in liver microsomes from immature female rats, adult female rats, and adult male rats, but only increased this enzyme activity by approximately 1-fold in liver microsomes from immature male rats. In conclusion, the extent of induction of hepatic microsomal glucuronyltransferase activity for 4-nitrophenol is affected dramatically by the age and sex of the animals.