Enhanced glutathione S-transferase (GST) activity in pregnant rats treated with benzo(a)pyrene

Administration of Benzo(a)pyrene (BP, 50 mg/kg/d) to pregnant rats significantly increased Glutathione S-transferase (GST) activity in placental tissue-extract (Vmax = 40 nmol/min/mg protein and 69 nmol/min/mg protein in controls versus treated animals respectively; P less than 0.01) and total fetal tissue-extract (Vmax = 51 nmol/min/mg protein and 82 nmol/min/mg protein in controls versus treated animals respectively; P less than 0.01) indicating an induction effect of BP on the GST system. An increase in the Km values was also observed: 1.61 x 10(-3) M and 2.84 x 10(-3) M in control versus treated placentae; 1.38 x 10(-3) M and 2.05 x 10(-3) M in control versus treated fetuses. A competitive effect on the enzyme by the BP present in the sample may also be involved. The glutathione content in both tissues did not show any changes after the treatment with BP. This increase in the GST system was not sufficient to protect the fetus. BP affected the reproductive performance of pregnant rats by significantly increasing the number of resorptions and fetal wastage, and, also, by decreasing the fetal weight.