Inhibition of Placental Amino Acid Uptake in Rats Following Acute and Chronic Ethanol Exposure

Abstract

The effects of acute and chronic maternal ethanol consumption on in vitro placental uptake of .alpha.-amino-isobutyric acid (AIB), cycloleucine, L-alanine (Ala), L-leucine (Leu) and L-lysine (Lys) were determined. Ethanol (4 g/kg, po [by mouth]) administered 2 h prior to sacrifice, reduced (P < 0.05) placental villous net uptake of cycloleucine and Ala by 29%. Prior chronic ethanol consumption depressed (P < 0.05) placental uptake of AIB (38%), cycloleucine (45%), Ala (35%), Leu (25%) and Lys (34%). In vitro exposure of previously untreated villous fragments for 2 h to 2 mg/ml of ethanol reduced (P < 0.05) the net uptake of AIB and cycloleucine by 24 and 31%, respectively; whereas the minimum concentration of acetaldehyde required to cause a significant inhibition was 310 .mu.M for AIB and 465 .mu.M for cycloleucine. Ethanol (3 mg/ml) had no effect on AIB or cycloleucine net uptake if Na was omitted from the incubation media. The efflux of AIB (10-6 M) and cycloleucine (10-6 M) from villous tissue was unaffected (P > 0.05) by either ethanol (3 mg/ml) or acetaldehyde (600 .mu.M) and obeyed 1st-order kinetics. Acute, and especially chronic, maternal ethanol consumption can depress the placental uptake of a variety of amino acids in the rat and, in the acute setting, the effect was on a Na-dependent system involved in amino acid influx into placental cells.