EFFECTS OF VOLUNTARY ETHANOL INGESTION ON THE POMC GENE EXPRESSION IN THE RAT PITUITARY AND ON THE PLASMA {beta}-ENDORPHIN CONTENT

Studies investigating the influence of chronic ethanol treatmenton the ß-endorphin content and the proopiomelanocortin(POMC) gene expression in the rat pituitary revealed contradictoryresults. Because of this we decided to start a more complexstudy to investigate the effects of isolation stress, chronicethanol treatment and voluntary ethanol consumption on the POMCmRNA level in the rat pituitary. The immediately prepared totalRNA from rat pituitaries was used in hybridization experiments(Northern- and Dot-blots). The results suggest a correlationbetween the POMC gene expression and the different fashionsof ‘living conditions’ tested. So the POMC geneexpression in long-term alcohol-treated animals was decreasedsupporting the theory of ß-endorphin deficiency inalcoholism. More interestingly, data obtained from the groupof voluntary ethanol consumption suggest an inverse correlationbetween total ethanol ingestion and POMC gene expression. Thisindicates the importance of the method of ethanol administration.Consistent with a decreased POMC gene expression in the pituitaryduring chronic ethanol treatment are previous studies showinga decrease in the plasma ß-endorphin content in suchsituations. Surprisingly, in the present study the plasma ß-endorphinlevels measured by radioimmunoassay were only slightly decreasedin chronically ethanol-treated rats. This may be due to dysregulatoryeffects of ethanol on post-translational processing, degradationand/or release of ß-endorphin.