THE ACUTE EFFECTS OF ETHANOL AND ACETALDEHYDE ON THE SYNTHESIS OF MIXED AND CONTRACTILE PROTEINS OF THE JEJUNUM

An investigation was made into the acute effects of ethanoland acetaldehyde with or without enzyme inhibitors of alcoholdehydrogenase (4-methylpyrazole) and aldehyde dehydrogenase(cyanamide) on fractional rates of protein synthesis of mixedand contractile proteins of the jejunum. Ethanol decreased thefractional rates of mixed and contractile protein synthesis(i.e. k_o defined as the percentage of tissue protein renewedeach day) by -25%. Pretreatment with 4-methylpyrazole followedby treatment with ethanol further reduced mixed and contractilek_o by -30%, when compared with saline plus saline and 4-methylpyrazoleplus saline groups. The greatest reductions in k_o of mixed andcontractile proteins occurred with cyanamide pretreatment followedby ethanol treatment: mixed and contractile protein k_o in thecyanamide plus ethanol group decreased by -60% when comparedwith saline plus saline and cyanamide plus saline groups, whereask_o decreased by -45% when compared with the saline plus ethanolinjected group. Acetaldehyde treatment alone caused no significantinhibition of protein synthesis. However, 4-methylpyrazole pretreatmentplus acetaldehyde treatment significantly reduced mixed andcontractile k_o by -20% when compared with the saline group,and by -15% when compared with the 4-methylpyrazole plus salineand saline plus acetaldehyde groups. These data show that ethanolalone and perhaps high levels of acetaldehyde may be responsiblefor the inhibition of intestinal protein synthesis and relatedpathological derangements, e.g. motility disturbances due toloss of contractile proteins.