EFFECTS OF ALCOHOL ON BETA-ENDORPHIN AND REPRODUCTIVE HORMONES IN THE MALE-RAT

In an attempt to examine the relationship between alcohol-induced alterations in immunoreactive beta-endorphin (i-beta-E) levels in the hypothalamic-pituitary-gonadal axis and the synthesis and release of reproductive hormones, male rats were treated with either an acute intraperitoneal injection of alcohol or were chronically exposed to an alcohol-containing liquid diet. Hypothalamic, pituitary, serum, and testicular levels of immunoreactive beta-endorphin (i-beta-E) and serum levels of luteinizing hormone (LH) and testosterone were measured at various times after initiation of these treatments. Testicular interstitial fluid (TIF) volumes and levels of TIF i-beta-E and testosterone were also measured 4 hr after acute treatment as an index of testicular release of these substances. Acute alcohol decreased pituitary levels of i-beta-E and increased serum levels of the peptide for up to 1 hr after its injection, but did not alter hypothalamic or testicular levels. Acute alcohol markedly increased TIF i-beta-E and decreased TIF testosterone and TIF volume. Sharp decreases in serum LH and testosterone were observed in association with these acute changes in i-beta-E levels in the pituitary, blood, and testes. During chronic alcohol exposure serum testosterone levels were substantially depressed, but tolerance appeared to develop quickly to the chronic effects of alcohol on serum LH. Similarly, tolerance to alcohol's effects on i-beta-E levels in the pituitary and serum also appeared to develop during chronic alcohol administration. However, hypothalamic and testicular i-beta-E levels were markedly suppressed by chronic alcohol administration in contrast to the lack of effect observed after acute alcohol administration. Our data demonstrate that both acute and chronic alcohol administration alter the functional activity of i-beta-E systems in the hypothalamic-pituitary-gonadal axis and suggest that these changes may be involved in alcohol's effects on reproductive endocrinology. Whether the effects we have observed are simply correlational in nature or demonstrate cause/effect relationships remains to be determined.