Benzo(a)pyrene hydroxylase activity in the whole implantation site, decidua, placenta and fetal membranes of the rat.

Abstract

Treatment of pregnant rats with 40 mg benzo(a)pyrene (BP) per kg body weight p.o. 24 h prior to sacrifice results in an induction of BP hydroxylase activity in the whole implantation site, the decidua, the placenta, and the fetal membranes. In control animals, no enzyme activity can be measured in these tissues with the exception of the fetal membranes which occasionally have a very low BP hydroxylase activity. In the BP-treated rats the enzyme activity is at least 3 to 6 times higher in the fetal membranes than in the placenta. The disappearance rate of BP hydroxylase activity was measured in the whole implantation site for 48 h after treatment with 40 mg BP kg body weight on day 8 of gestation. In the whole implantation site, the maximum enzyme induction is observed within 18 h while 48 h after BP-treatment, the enzyme activity is very low. The disappearance rate of BP hydroxylase activity was also measured for 48 h in the placenta on day 12 and on day 19 of gestation, respectively. In the placenta the height of enzyme induction remains almost unchanged within a 48 h interval. After BP-treatment of rats, morphological alterations can be observed in the decidua which are characterized by a moderate enlargement of the vesicles of the rough endoplasmic reticulum while this treatment does not effect the fine structure of the fetal membranes.