Effect of chronic ethanol on reproductive and growth hormones in the peripubertal male rat

Ethanol (EtOH) has previously been shown to have profound effects on various endocrine systems. The present study further investigates the action of EtOH on testosterone and on the GH-IGF-I axis. Since these hormones are particularly important in male rats progressing through puberty, we examined the effect of 10 days of EtOH treatment at three different ages (35, 50 and 65 days old) as male rats progressed through puberty into adulthood. After 10 days of feeding a 6% EtOH liquid diet, serum testosterone levels were markedly decreased in all three ages (P < 0.02 at 35 days, P < 0.01 at 50 days and P < 0.03 at 65 days). IGF-I was assessed and was differentially affected at each age. At 35 days IGF-I levels were suppressed by EtOH (P < 0.0002), at 50 days no change was apparent, and at 65 days levels were significantly higher in EtOH-treated (P < 0.01) compared with liquid-fed controls. The levels of IGF-I in the EtOH-treated animals paralleled pituitary GH mRNA levels with a significant fall in the expression of GH mRNA levels noted at 35 days (P < 0.04), no change at 50 days and a significant rise observed at 65 days (P < 0.03). At the hypothalamic level, GH-releasing hormone (GRF) mRNA was significantly reduced in the two younger EtOH-treated age groups compared with controls (P < 0.04 at 35 days; P < 0.02 at 50 days). At 65 days of age, EtOH did not alter GRF mRNA levels. No EtOH-induced changes were seen in GRF content at any age. These observations indicate definite age-related alterations in hormonal gene expression and circulating serum hormone levels and emphasize the importance of studying these critical peripubertal ages after chronic EtOH exposure.