Influence of thiamine deficiency on the response to ethanol in two inbred rat strains.

We investigated whether thiamine deficiency (TD), a frequent concomitant of chronic alcoholism, differentially modifies the response to ethanol in two inbred rat strains with highly different genetic susceptibilities to development of TD encephalopathy. Ethanol-induced (3 g/kg i.p.) behavioral impairment and hypothermia were studied after 2, 5 and 7 weeks of TD and after 6 weeks of repletion on normal diet. Controls of the M520/N (TD-sensitive) strain metabolized ethanol more rapidly, had a greater liver to body weight ratio, greater total body water, earlier and lower peak blood ethanol concentrations (BEC), diminished area under the BEC curve and lesser behavioral impairment and hypothermia (even at equivalent BEC values) than those of the F344/N (TD-resistant) strain. In both strains, TD resulted in reduced ethanol metabolic rate and liver to body weight ratio and equivalent ethanol-induced hypothermia and behavioral impairment at lower BEC. Lower and delayed peak BEC and unchanged area under the BEC curve suggest an increased volume of ethanol distribution during TD. Recovery appeared complete after 6 weeks of normal diet. Both strains lost an equivalent proportion of body weight during TD but M520/N rats had lesser decrements in ethanol metabolic rate, had greater reductions in liver weight, peak BEC and baseline body temperature and developed overt encephalopathy whereas F344/N rats did not. Therefore, in the chronic alcoholic, TD may modify ethanol's effects via pharmacokinetic and pharmacodynamic mechanisms. Relatively high ethanol tolerance of the strain with a genetic predisposition to TD encephalopathy is consistent with the hypothesized role of this avitaminosis in the pharmacogenetics of alcoholism.