Ethanol-Induced Alterations in the Posttranslational Processing, But Not Secretion of Luteinizing Hormone-Releasing Hormone In Vitro

The effects of ethanol (EtOH) on the male hypothalamic pituitary reproductive axis are multiple and varied. Although direct gonadal toxicity has been reported, hypothalamic-pituitary perturbations have also been noted. The difficulty of sampling the hypothalamus has made direct investigation of EtOH-induced alterations on luteinizing hormone-releasing hormone (LHRH) fraught with interpretation problems. To circumvent this, we have conducted a series of experiments exploring the effect of 200 mg% EtOH in vitro on GT1-7 cells, a newly developed LHRH secreting neural cell line. Cell lines were treated with EtOH-containing or EtOH-free media for 2,6,24, or 48 hr. EtOH caused no significant change in LHRH secretion at any time point, although there was a trend to increased secretion after 2 hr EtOH exposure when compared with control. Significantly increased total (i.e., cellular plus secreted) pro-LHRH coupled with significantly reduced cellular LHRH after 6 hr only of EtOH exposure suggested that EtOH caused a transient decrease in processing from bioinactive pro-LHRH to bioactive LHRH. However, even at this time point, LHRH secretion from these EtOH-exposed cells was no different than from control cells. Steady-state LHRH mRNA levels were not changed by EtOH at any time point. These findings are concordant with previous in vitro data using hypothalamic tissue that has similarly demonstrated no effect of EtOH on LHRH secretion. Taken together with the in vivo demonstration that EtOH reduces hypothalamic-pituitary portal blood levels of LHRH, these data indicate that EtOH exerts its effect either at an extrahypothalamic locus and/or on non-LHRH-producing cells within the hypothalamus.