Zinc concentrations in two strains of mice after free choice and forced ethanol exposure

Abstract

from lack of control over the specific radioactivity of the precursor amino acid during the incorporation period. In the present study the rate of protein synthesis was measured in anaestheiized rats, using a continuous, intravenous infusion of valine (specific radioactivity 3.33 pCi/mol), lasting for 30 min. The specific radioactivity of valine was measured to be fairly constant from 11 min onwards. Liver specimens were taken at 11, 20 and 30 min. The protein synthesis rate was calculated from valine-specific radioactivity in protein and in the intracellular precursor pool measured from 11 to 30 min. The rats were pair-fed either a diet containing ethanol (9.2 g/kg per rat per day) or a control diet, in which lipid replaced ethanol isoenergetically, for 58 65 days. The animal growth rate was not significantly different between the groups (2.8 g/day in the ethanol-treated US. 2.9 g/day in controls). All animals were fasted for approximately 16 h before measurement of protein synthesis. In addition, some rats received an i.p. injection (1 ml/kg) of either saline or dexamethasone (4 mg/kg) 1 h prior to measurement of protein synthesis. Chronic ethanol treatment reduced the in uiuo protein synthesis rate by 37% from a control rate of 86.0 + 5.9 nmoles valine per 100 g body weight per min (a = 0.002). This reduction became less marked when the rats received an i.p. injection of saline and disappeared completely when given dexamethasone i.p. 1 h before measurement of protein synthesis. Thus ethanol-treated rats given dexamethasone i.p. had a significantly higher rate of protein synthesis than ethanol-treated rats given nothing or saline (a < 0.05). Our observations demonstrate that the handling procedure preceding the measurement of protein synthesis could be of critical importance to the outcome of the experiments. This could explain some of the controversies in the literature on ethanol effects on rates of protein synthesis.