THE INFLUENCE OF AGE AND SOME INDUCERS ON UDP-GLUCURONOSYLTRANSFERASEACTIVITY

UDP-glucuronyltransferase (UDP-GT) activity was examined in male Wista r rats aged 0.5, 1, 2, 4, 8, 12, 20, and 28 months. The rats were trea ted with phenobarbital (75 mg/kg, 72 and 48 h before death), beta-naph thoflavone or dexamethasone (40 mg/kg and 20 mg/kg, respectively, for three days before death). Prior to decapitation the rats were fasted f or 12 h. Hepatic microsomes were prepared according to the method of D allner. UDP-GT activity was determined by the method of Burchell and W eatherill. p-Nitrophenol was used as an aglucone. UDP-GT activity decr eased rapidly in the control rats aged from two weeks to four months. In the older control rats the activity tended to increase. Two-week-ol d rats treated with phenobarbital showed a slightly increased UDP-GT a ctivity. In the older animals (up to one year) UDP-GT activity increas ed to 150% of the control value and stayed at this level in the remain ing age groups. beta-Naphthoflavone was a more potent inducer of UDP-G T than phenobarbital. The activity of beta-naphthoflavone-induced UDP- GT was low in the youngest rats. It was about 180% in two-month-old ra ts and reached 260% of the control value in eight-month-old rats. Alth ough the activity decreased in the older rats, it still exceeded 200%. Dexamethasone did not affect UDP-GT activity. Only in two-week-old an d two-month-old rats did we observe a slight increase in the activity of UDP-GT. (C) 1997 Elsevier Science Inc.