ETHANOL (E) METABOLISM IN PREGNANCY (P) AS DETERMINED BY THE [14C] ETHANOL BREATH TEST (EBT)

Maternal E consumption in P poses a known risk to the mother and fetus. The purpose of this study was to determine the effects of P on in vivo metabolism of E. The in vivo rate of E metabolism can be monitored by the EBT by measuring the rate of CO2derived from the metabolism of radiolabeled E (Toxicol Appl Pharmacol, 61:177, 1981). The EBT was conducted in 7 pregnant (Pg) and 5 nonpregnant (Npg) C57/B6J mice of similar ages. Day 0 was when vaginal plugs were found or when Npg mice were entered into the protocol. The EBT was conducted on days 6,8,10,14, and 16. [14C] E (5×105dpm) and unlabeled E (50 mg/kg) were administered i.p. The mice were immediately placed in air collection chambers, 14CO2was collected by bubbling exhaled air through an alcohol trapping solution and then a CO2trapping solution of ethanolamine methanol, and the rate of 14CO2exhaled was determined. The elimination rate constant (Kel) of labeled CO2was calculated and used as the measurement parameter of E clearance. The Kel did not change for Npg mice. In the Pg mice, the Kel did not differ from that of Npg mice on day 6 or 10 of gestation, but was increased on day 8 (Npg Kel=0.0592±0.002, Pg Day 8 Kel=0.0698±0.003; p<.001) and was decreased on days 14 and 16 (0.0525±0.002 and 0.0501±0.002, respectively; p<.001 vs. Npg). In summary, the rate of E metabolism in P changes biphasically. The rate of E metabolism as determined by the EBT increased significantly during organogenesis but decreased in late P.