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 acetaldehyde with or without enzyme inhibitors of alcohol dehydrogenase (4-methylpyrazole) and aldehyde dehydrogenase (cyanamide) on fractional rates of protein synthesis of mixed and contractile proteins of the jejunum. Ethanol decreased the fractional rates of mixed and contractile protein synthesis (i.e. ks, defined as the percentage of tissue protein renewed each day) by approximately 25%. Pretreatment with 4-methylpyrazole followed by treatment with ethanol further reduced mixed and contractile ks by approximately 30%, when compared with saline plus saline and 4-methylpyrazole plus saline groups. The greatest reductions in ks of mixed and contractile proteins occurred with cyanamide pretreatment followed by ethanol treatment; mixed and contractile protein ks in the cyanamide plus ethanol group decreased by approximately 60% when compared with saline plus saline and cyanamide plus saline groups, whereas ks decreased by approximately 45% when compared with the saline plus ethanol injected group. Acetaldehyde treatment alone caused no significant inhibition of protein synthesis. However, 4-methylpyrazole pretreatment plus acetaldehyde treatment significantly reduced mixed and contractile ks by approximately 20% when compared with the saline group, and by approximately 15% when compared with the 4-methylpyrazole plus saline 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 pathological derangements, e.g. motility disturbances due to loss of contractile proteins.