Effects of Chronic Ethanol Treatment on the In Vitro Biosynthesis of Pro‐Opiomelanocortin and ItsPosttranslational Processing to (β‐Endorphin in theIntermediate Lobe of the Rat Pituitary

Abstract

Chronic treatment of rats with 15% (vol/vol) ethanol in tap water as their only source of liquid over a period of 3 weeks resulted in a strong decrease by almost 50% in tissue levels and in vitro release of immunoreactive β-endorphin of the neurointermediate pituitary. Moreover, the in vitro incorporation of [³H]phenylalanine into peptides of the neurointermediate pituitary, immunoprecipitable with β-endorphin antiserum, was found to be decreased by more than 30%. Analysis of β-endorphinrelated peptides on sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that chronic ethanol treatment reduced the in vitro biosynthesis of the β-endorphin precursor pro-opiomelanocortin. This ethanol-induced effect was combined with a retardation in the time course of the posttranslational processing of the precursor into β-endorphin. Thus, chronic ethanol treatment may influence the activity of enzymes which process the opioid peptide precursor pro-opiomelanocortin, leading to a decreased formation of the final secretory product β-endorphin.