Oxidative biotransformation of 2-acetylaminofluorene in fetal and placental tissues of humans and monkeys. Correlations with aryl hydrocarbon hydroxylase activities

Abstract

The mixed-function oxidation of 14C-labled 2-acetylaminofluorene (AAF) was investigated in placental and fetal tissues of humans and monkeys (Macaca nemestrina) in vitro. The major metabolite formed in most tissues was 7-hydroxy-AAF. Rates of the hydroxylation reactions varied widely among the tissues investigated and were generally one to two orders of magnitude lower than those measured in rat hepatic tissues. High correlations among rates of 7-,5-, and 3- and between 1- and N-hydroxylations of AAF were observed. The latter two reactions were less responsive to inhibition by carbon monoxide. Rates of 3-hydroxylations of benzo[a]pyrene (BP) also were highly correlated with rates of 7-, 5-, and 3-hydroxylations of AAF but were not correlated with rates of 1- and N-hydroxylations in human placental microsomes. A lack of statistically significant correlations was observed among rates of many of these hydroxylation reactions studied in primate fetal tissues. Rates of 7-, 5-, and 3-hydroxylations of AAF were not statistically correlated with rates of 3-hydroxylation of BP in homogenates of primate fetal tissues in most instances, but statistically significant correlations among rates of 3-hydroxylation of BP and 1- and N-hydroxylations of AAF were observed in those preparations. The results suggested two separate mechanisms for the genetic control of rates of placental aromatic ring- and N-hydroxylation reactions as opposed to apparent multiple genetic controls for rates of these hydroxylation reactions in primate fetal tissues.