Effect of maternal ethanol consumption on foetal and neonatal rat hepatic protein synthesis

Abstract

Effects of maternal ethanol consumption were investigated on the rates of protein synthesis by livers of fetal and neonatal rats in vivo and in vitro, and on the activities of enzymes involved in protein synthesis and degradation. The rates of general protein synthesis by ribosomes in vitro studied by measuring the incorporation of [14C]leucine into ribosomal protein showed that maternal ethanol consumption resulted in an inhibition of the rates of protein synthesis by fetal and neonatal livers from the ethanol-fed group. The rates of incorporation of i.v. injected [14C]leucine into hepatic proteins were significantly lower in the fetal, neonatal and adult livers from the ethanol-fed group. Incubation of adult-rat liver slices with ethanol resulted in an inhibition of the incorporation of [14C]leucine into hepatic proteins; this effect was not observed in the fetal liver slices. This effect of externally added ethanol was at least partially prevented by the addition of pyrazole to the adult liver slices. Pyrazole addition to fetal liver slices was without significant effect on the rates of protein synthesis. Cross-mixing experiments showed that the capacity of both hepatic ribosomes and pH 5 enzyme fractions to synthesize protein was decreased in the fetal liver from the ethanol-fed group. Maternal ethanol consumption resulted in a decrease in hepatic total RNA content, RNA/DNA ratio and ribosomal protein content in the fetal liver. Fetal hepatic DNA content was not significantly affected. Ethanol consumption resulted in a significant decrease in proteolytic activity and the activity of tryptophan oxygenase in the fetal, neonatal and adult livers. It is possible that the mechanisms of inhibition of protein synthesis observed here in the fetal liver after maternal ethanol consumption may be responsible for at least some of the changes observed in fetal alcohol syndrome.