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 ethanol and acetal dehyde with or without enzyme inhibitors of alcohol dehydrogenase (4-m ethylpyrazole) and aldehyde dehydrogenase (cyanamide) on fractional ra tes of protein synthesis of mixed and contractile proteins of the jeju num. Ethanol decreased the fractional rates of mixed and contractile p rotein synthesis (i.e. k(s), defined as the percentage of tissue prote in renewed each day) by similar to 25%. Pretreatment with 4-methylpyra zole followed by treatment with ethanol further reduced mixed and cont ractile k(s) by similar to 30%, when compared with saline plus saline and 4-methylpyrazole plus saline groups. The greatest reductions in k( s) of mixed and contractile proteins occurred with cyanamide pretretme nt followed by ethanol treatment: mixed and contractile protein k(s) i n the cyanamide plus ethanol group decreased by similar to 60% when co mpared with saline plus saline and cyanamide plus saline groups, where as k(s) decreased by similar to 45% when compared with the saline plus ethanol injected group. Acetaldehyde treatment alone caused no signif icant inhibition of protein synthesis. However, 4-methylpyrazole pretr eatment plus acetaldehyde treatment significantly reduced mixed and co ntractile k( )s by similar to 20% when compared with the saline group, and by similar to 15% when compared with the 4-methylpyrazole plus sa line and saline plus acetaldehyde groups. These data show that ethanol alone and perhaps high levels of acetaldehyde may be responsible for the inhibition of intestinal protein synthesis and related pathologica l derangements, e.g. motility disturbances due to loss of contractile proteins.