Effects of Chronic Ethanol Diet on Pituitary-Testicular Function of the Rat1

We studied the effects of a 6% ethanol liquid diet administered for 5 wk on the pituitary-gonadal function of adult male rats. Because ethanol is known to reduce body weight, we used sucrose-fed animals as controls. No significant differences in body, testis, or prostate weights were found between the rats exposed to ethanol and their sucrose-fed controls at the end of the 5-week treatment. Seminal vesicle weights decreased significantly (p<0.05) in the ethanol-treated group. Serum and testicular testosterone concentrations were significantly reduced in the ethanol-treated group, to 43.6% and 48.3% of levels in the sucrose-fed controls, respectively (p<0.05). Serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels of the ethanol-treated rats were 37.9% and 41.3%, respectively, of those of the sucrose-fed controls (p<0.01 – 0.05). The pituitary levels of these hormones were similar to those of controls, but the ratios of pituitary LH and FSH to their serum levels were clearly increased after ethanol exposure, to 492% and 206.1%, respectively (p<0.05). In contrast, pituitary prolactin (PRL) of the ethanol-treated rats was decreased to 40.2% (p<0.01) of sucrose-fed controls. Testicular content of LH receptors was significantly reduced (to 77.0% of controls; p<0.01), but content of FSH receptors was slightly increased by the ethanol diet (to 121.5% of sucrose-fed controls; p<0.05). No ethanol-associated changes were apparent in testicular PRL and gonadotropin-releasing hormone (GnRH) receptors or in pituitary GnRH receptors. The increased ratio of pituitary/serum gonadotropins upon ethanol treatment indicates that the release of gonadotropins is affected more than their synthesis. This effect is probably caused by changes in hypothalamic GnRH secretion, which may be sufficient to maintain the pituitary GnRH receptors and gonadotropin synthesis, but not to sustain normal LH and FSH release. The present data on effects of a 5-wk ethanol exposure differ considerably from those found by us recently after a short-term exposure (7 days) and emphasize that both in vivo models are important for studying effects of ethanol on male reproductive functions.