Resolution and reconstitution of human placental monooxygenase activity responsive to maternal cigarette smoking

Human placental cytochrome P-450 monooxygenase activity toward 7-ethoxyresorufin increases in response to maternal cigarette smoking and is specifically inhibited in vitro by 7,8-benzoflavone. Using a mixture of ionic and nonionic detergents we have solubilized placental cytochrome P-450 CO binding and cytochrome C reductase activities and separated them by anion exchange chromatography. Fractions containing cytochrome P-450 from placentas from smokers will catalyze 7,8-benzoflavone-inhibitable activity in reconstituted systems. SDS polyacryl-amide gel electrophoresis reveals proteins (molecular weight 70,000-40,000) in cytochrome P-450-containing fractions, derived from women who smoke, which are not detected in material from nonsmokers. These findings support the contention that placental response to maternal smoking involves induction of cytochrome P-450.