Effect of cadmium on some enzyme activities in first-trimester human placentae

Explants from first-trimester placentae obtained from non-smoking women were incubated with doses of 0, 0.75, 1.5, 3, 6 and 12 micrograms of cadmium (Cd) as CdCl2 for 6 or 24 h. At the end of the incubation period, the activities of placental aryl hydrocarbon hydroxylase (AHH) (a phase I enzyme), quinone reductase (QR) and catecholamine-O-methyltransferase (COMT) (both phase II enzymes) and glucose-6-phosphate dehydrogenase (G-6-PD) were determined. Cd at low dose levels increased significantly the activities of placental phases I and II enzymes in a time- and dose-dependent manner. Of the first 3 enzymes, only AHH showed a biphasic response for the two time periods, with the activities of QR and COMT continually increasing at all the dose levels tested for the two incubation periods. However, the G-6-PD activity was inhibited at all the dose levels of Cd, the effect being very drastic after exposure to 0.75 ppm Cd for both incubation periods.