Effect of benzo(α)pyrene treatment on the benzo(α)pyrene hydroxylase activity in maternal liver,placenta, and fetus of the rat during day 13 to day 18 of gestation

Summary Pregnant rats were treated with an oral dose of 40.0 mg benzo() pyrene (BP) per kg body weight and were sacrificed 24 h later. Maternal liver, placenta, and fetus were assayed for BP-hydroxylase activity. The enzyme activity was measured from day 13 to day 18 of gestation. Pretreatment of rats with BP results in an approximately 15-fold increase of BP-hydroxylase activity in the maternal liver compared to the enzyme activity in the liver of control animals. These enzyme levels were maintained throughout the duration of gestation.No BP-hydroxylase activity could be measured in the fetus and the placenta of control animals. After treatment with BP maximal induction of BP-hydroxylase activity in the placenta was not achieved before day 15 of gestation. BP treatment resulted in a detectable enzyme activity in the fetus. However, the degree of induction increased with the age of the fetus. Electron microscopic pictures demonstrate a swelling and enlargement of the endoplasmic reticulum (ER) in the trophoblast cell of the placenta after BP treatment. In the fetal liver the ER is characterized by a moderate enlargement while there is no effect in the maternal liver after treatment of the animals with BP.This work was supported by a grant from the Deutsche Forschungsgemeinschaft given to the Sonderforschungsbereich 29, Embryonale Entwicklung und Differenzierung (Embryonal-Pharmakologie).Parts of this work were presented at the Spring Meeting of the German Pharmacological Society held in Mainz, March 1971.