HUMAN PLACENTAL CYTOCHROME-P450 AND QUINONE REDUCTASE ENZYME-INDUCTION IN RELATION TO MATERNAL SMOKING

Components of cigarette smoke such as cadmium and polycyclic aromatic hydrocarbons have been shown to induce quinone reductase (QR) activity in placental explants. This study examines the relationship of matern al smoking habit and maternal plasma cotinine concentration with the a ctivities in vitro of both QR and the cytochrome P450 (CYP1A) marker e thoxyresorufin O-deethylase (EROD) in placental tissue. Maternal plasm a samples were taken at Week 34 of gestation, and placental tissues we re obtained at term. Plasma cotinine concentrations were determined by high-performance liquid chromatography. Trophoblast cytosolic QR and microsomal EROD activities were measured by resazurin reduction and et hoxyresorufin O-dealkylation respectively. QR activity was inhibited 7 0% by a mixture of dicoumarol (1 mu M) and rutin (20 mu M) Plasma coti nine concentrations correlated significantly (P < 0.001) with both dec lared smoking rate (r = 0.67, N = 37) and placental EROD activity (r = 0.63, N = 36), but not with QR activity, whether measured as total QR activity or specifically as either DT-diaphorase or carbonyl reductas e. It is concluded that smoking up to 40 cigarettes per day induces ER OD but does not affect QR activity in the placenta at term.