Inhibition of placental valine uptake after acute and chronic maternal ethanol consumption

The effects of acute and chronic maternal ethanol intake on the in vitro uptake of valine (Val) by rat placental villous fragments were determined. Ethanol (4 g/kg), given by intubation to 16- or 20- day pregnant dams 2 hr before sacrifice, reduced subsequent in vitro placental uptake of Val by 31 and 40%, respectively (P <.05). This effect was not mediated by ethanol induced hypothermia. When ethanol (4 g/kg each 12 hr) was administered on days 11 to 13 or days 14 to 16 of gestation, placental villous uptake of Val, as measured on day 20 of gestation, was reduced by 24 and 28%, respectively (P <.05). Maternal chronic ethanol consumption for 30 days before and throughout gestation induced a 44% depression (P <.05) in in vitro placental Val uptake tested on day 20. In vitro exposure of previously untreated placental villous fragments to ethanol or acetaldehyde for a 2-hr preincubation and a 10-min incubation with [ ¹⁴C]Val, showed that ethanol-reduced Val uptake at concentrations as low as 1.0 mg/ml (P <.05), whereas acetaldehyde levels of 465 μM were needed to cause a significant inhibition. Placental villous fragments accrue Val by a concentrative process that is temperature, sodium, and energy-dependent and is partially inhibited by ouabain. Neither ethanol nor acetaldehyde (3 mg/ml and 620 μM, respectively) exert an effect (P >.05) on villous Val uptake if sodium is excluded from the incubation media. It is concluded that acute and chronic maternal ethanol consumption can significantly alter placental Val uptake measured in vitro and that a direct effect of ethanol on a sodium-dependent Val transport system may be one of the mechanisms involved. This phenomenon may be one mechanism by which maternal ethanol consumption induces deficits in fetal growth and development.