Modifications of carcinogen metabolism in hepatic microsomes of suckling young by 3-methylcholanthrene or beta-naphthoflavone administered to lactating rats

Neonatal modulation of adult rat hepatic microsomal benzo[a]pyrene hydroxylase activities by Aroclor 1254 or phenobarbital

The constitutive and Aroclor 1254-induced activities of hepatic microsomal benzo[a]pyrene hydroxylases in male and female rats were determined in animals from ages 11 to 120 days. In 11-day-old noninduced male rats, benzo[a]pyrenediones and 9-hydroxybenzo[a]pyrene were the major microsomal metabolites; in 21-day-old males benzo[a]pyrene-diones and benzo[a]pyrene-9,10-dihydrodiol were predominant. In 60- and 120-day-old animals 3-hydroxybenzo[a]pyrene was the major microsomal metabolite. A similar trend was observed for the development of benzo[a]pyrene hydroxylase activities in female rats. With the exception of 4,5-dihydrodiol formation, the highest induction of individual and total benzo[a]pyrene hydroxylase activities by Aroclor 1254 was observed in the 21-day-old immature male rats, in which there was a 330- and 4.5-fold increase in the formation of 3-hydroxybenzo[a]pyrene and quinone metabolites, respectively. The induction of benzo[a]pyrene total metabolite formation by Aroclor 1254 in female rats from 11 to 120 days of age was relatively constant (i.e., 13.3- to 10.1-fold induction); however, the relative induction of the individual benzo[a]pyrene hydroxylases was highly variable. In a second set of experiments, male and female rats were neonatally exposed to phenobarbital (600 mumol/kg) or Aroclor 1254 (100 mumol/kg), and the effects of these xenobiotics on neonatal imprinting of hepatic microsomal benzo[a]pyrene hydroxylase activities were determined in the 120-day-old animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Sex hormone-mediated effects on the phase I and phase II metabolism of N-2-fluorenylacetamide. Modulation of 9-hydroxylation

Sex differences in the phase I (cytochrome P-450-catalyzed hydroxylations) and phase II (conjugations) metabolism of N-2-fluorenylacetamide (2-FAA) by the livers of 50-day-old Sprague-Dawley rats and effects of gonadectomy were determined. The higher level (1.4 times) of cytochrome P-450 in the microsomes of male rats correlated with their 8 and 1.3 times greater capacities to form 9-hydroxy(OH)-2-FAA and 7-OH-2-FAA respectively. One week after gonadectomy, the formation of 9-OH-2-FAA, the major metabolite in the male, was decreased by 70%, whereas in the female it was increased 1.3 times. Treatment of male rats with beta-naphthoflavone (beta-NF) increased the formation of phenolic metabolites and N-OH-2-FAA, but decreased that of 9-OH-2-FAA. The amounts of 9-OH-2-FAA were increased, however, in beta-NF-treated female and gonadectomized male rats. These sex hormone- and beta-NF-mediated differences in the extent of 9-hydroxylation of 2-FAA are discussed in relation to the fluctuations in the levels of specific cytochrome P-450 isozymes. In contrast to the phenolic metabolites and N-OH-2-FAA, 9-OH-2-FAA was a poor substrate for UDP-glucuronyltransferase; this conjugation was not induced by treatment of male rats with beta-NF. Hence, in the presence of male hormones, relatively large amounts of 9-OH-2-FAA were formed and possibly retained in the liver. A role of this alcohol as a potential promoter in hepatocarcinogenesis by 2-FAA is suggested.