The Impact of Acute Ethanol on Reproductive Hormone Synthesis, Processing, and Secretion in Female Rats at Proestrous

It is the purpose of this study to investigate the effects of acute ethanol (EtOH) on the female rat hypothalamic-pituitary-gonadal (HPG) axis. The molecular and cellular mechanistic details of such effects have been studied intensively in the male rat. However, there has been relatively little in-depth study of EtOH's effects on the adult, postpubertal female rat. Adult female rats with confirmed 4- or 5-day estrous cycles were given a single injection of EtOH or saline between noon and 1:00 PM on proestrous and were killed at 4:00 PM. EtOH caused a sharp 97% reduction in luteinizing hormone (LH) serum levels (p < 0.001), compared with controls with no concomitant change in LH mRNA. EtOH also significantly reduced hypothalamic LH releasing hormone (LHRH) by 49% (p < 0.01), with no change in content of the precursor pro-LHRH compared with saline-injected controls. The ratio of LHRH to pro-LHRH was also significantly reduced by EtOH (p < 0.05), compared with control. There was no EtOH-induced change in LHRH mRNA. Compared with saline, EtOH reduced both serum estradiol by 37% (p < 0.02) and progesterone by 47% (p < 0.001). These results show that EtOH has profound disruptive effects on the female HPG axis. Our data suggests that EtOH decreases the releasable LHRH pool either by decreasing conversion of pro-LHRH to LHRH and/or by increasing local LHRH degradation. This acutely restricts the release of LH and subsequent estradiol and progesterone secretion.