Conscious mature and immature rats were administered either saline or an ethanol (ETOH)-saline solution via a permanent intragastric cannula, and plasma growth hormone (GH) levels were measured by radioimmunoassay of external jugular blood samples drawn every 10 min through an indwelling Silastic catheter. Control injections of saline into the gastric cannula did not modify plasma GH concentrations, whereas both groups of rats which were administered ETOH showed significant decreases in plasma GH concentrations and no evidence of the pulsatile secretion of the hormone. Comparable increases in the area under the GH curve occurred following a challenge dose of GH-releasing factor in both saline- and ETOH-injected rats, indicating that pituitary responsiveness was the same for both groups. These results indicate that ETOH is capable of altering GH secretion in adult as well as prepubertal animals, via an action at the hypothalamic level.
To more completely assess the means by which alcohol impairs the female reproductive cycle in rats, we have measured hypothalamic luteinizing hormone-releasing hormone (LHRH), pituitary LHRH receptor content, and the serum levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin (Prl), and progesterone (P). After two successive cycles, the animals began receiving either an alcohol or a isocaloric control liquid diet regimen beginning on the first day of diestrus, with continued monitoring of the estrous cycle throughout the experiment. An additional set of controls consisted of animals maintained on lab chow and water provided ad libitum. Our results indicate that those animals receiving the control diets showed uninterrupted estrous patterns, whereas those animals receiving the alcohol diet remained in diestrus. Additionally, the alcohol-treated animals showed an increase (p less than 0.05) in LHRH content, with a concomitant decrease (p less than 0.01) in serum LH, and an increase (p less than 0.01) in serum Prl. No significant differences were detected in serum FSH levels or pituitary LHRH receptor content. No differences were detected in serum P levels. These results indicate that short-term alcohol administration disrupts the female reproductive cycle, causing persistent diestrus, and support our hypothesis that the alcohol-induced depression in serum LH levels is due to a diminished release rate of hypothalamic LHRH.
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