Gonadotropin secretion in infantile rats exposed to ethanol in utero

Previous studies have shown that fetal alcohol exposure (FAE) alters reproductive function in both male and female rats. In females, FAE delays the onset of puberty, reduces a preovulatory-like LH surge, and results in an early onset of acyclicity. In males exposed to ethanol in utero, the perinatal surge of testosterone is reduced. During the infantile period of the female rat, there is a dramatic increase in plasma follicle-stimulating hormone (FSH), which is thought to play a role in initiating ovarian activity and perhaps the onset of puberty. In this study, we determined the effects of FAE on the patterns of gonadotropin secretion during the infantile period [postnatal days (PND) 8-21] in both male and female rats. Timed pregnant dams were fed a liquid diet containing 35% ethanol-derived calories during the final week of gestation. Control dams were fed either an isocaloric diet with sucrose substituted for ethanol (pair fed, PF) or laboratory chow (chow fed, CF). Male and female pups were sacrificed on PND 8, 10, 12, 15, 18, and 21, and trunk blood was collected. In males, LH levels decreased to a nadir on PND 18, and this decrease was blunted by FAE (p < 0.05). In contrast, FSH secretion was not altered by FAE. In females, plasma FSH levels were greater than males, and increased to peak on PND 12. This FSH peak was significantly delayed in FAE females (p < 0.02). There was no age-related change in LH levels in FAE females, and LH levels were not altered by FAE. The delayed peak of FSH secretion by FAE correlates with the delay in puberty previously seen in females. To investigate this further, we examined the possibility that the delay in the peak of serum FSH in FAE females is due to a reduced number of FSH-producing gonadotrophs. FSH-containing gonadotrophs were identified by immunocytochemistry. Cell counts of FSH-immunoreactive cells in pituitaries from PND 8, 15, and 21 control-fed and FAE female rats showed developmental increases in the number of FSH gonadotrophs per unit area (p < 0.001), but no treatment differences were observed. Overall, these data show that fetal alcohol exposure can alter gonadotropin secretion in infantile life in male and female rats. Importantly, the delay in FSH secretion in females may ultimately play a role in the delay in puberty observed in the FAE female rat.