Effect of an aproteic diet on gonadotropin release response to GnRH and estrogen-progesterone in rats

The fasting-induced gonadotropin function decrease is unspecific, because in this situation there is a lack of all nutrients. We report here the effect of specific protein lack in the diet during 21 days, on pituitary gonadotropin synthesis and response to exogenous GnRH in adult male rats. We also studied the effect of the aproteic diet (AP) on the positive feedback mechanism in adult female castrated rats. The AP diet decreased significantly, both LH and FSH pituitary concentration and also basal gonadotropin plasma levels in male rats. GnRH produced a significantly increment in LH secretion in both treated and control groups, reaching similar levels after stimulation. Nevertheless, the percentile increment from basal levels in the aproteic group was almost four times the controls, suggesting an increased sensitivity in pituitary response to GnRH in rats fed with AP diet. In female castrated rats, the aproteic diet imposed 3 weeks after the surgery was unable to reduce basal gonadotropin secretion, and so also prolactin secretion. Estradiol/progesterone (EP) administration produced the activation of positive feedback mechanism, increasing significantly LH and FSH secretion in both controls and AP groups. Nevertheless, both gonadotropin responses to EP were significantly greater in rats fed with AP diet. Basal prolactin levels and response to EP were not different between both groups. This results suggest that selective protein lack in a diet, reduced pituitary LH and FSH synthesis and secretion. This type of diet also increments pituitary sensitivity to GnRH administration in male rats, and gonadotropin response to positive feedback mechanism in female rats.