Conversion of ethanol to acetaldehyde by human placental homogenates and villi in vitro

The authors have previously reported that placental villi in vitro metabolize acetaldehyde (Ach), and that Ach forms adducts with placental subcellular fractions. In the experiments reported here the authors have investigated the capacity of placental homogenates and villi to generate Ach from ethanol (EtOH). When placental homogenates (0.5 g wet weight) prepared in 50 mM Tris. pH 7.5, were incubated with 20 μM [1-14C]ethanol and an NADP- generating system, Ach was formed at the rate of 0.18 nmol/h/g wet weight of tissue, based on counts trappable with semicarbazide. NAD was as effective as NADP. Omission of cofactor resulted in a 69% decrease in activity. The addition of a human serum ultrafiltrate (25,000 m.w. cut-off) to 20% had no effect on Ach formation, whole serum at 20% reduced reaction by 60%. Sodium azide at 40 mM completely abolished Ach formation, 1,10-phenanthroline at 0.4 mM inhibited approximately 50%. In contrast, no Ach formation was detected when 1.0-g fragments of villous tissue were incubated with 20 μM [1-14C]EtOH. The data suggest that villous tissue is capable of Ach formation by a catalase-like activity, but the capacity of intact villi for EtOH oxidation is low