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 i n this situation there is a lack of all nutrients. We report here the effec t of specific protein lack in the diet during 21 days, on pituitary gonadot ropin synthesis and response to exogenous GnRH in adult male rats. We also studied the effect of the aproteic diet (AP) on the positive feedback mecha nism in adult female castrated rats. The AP diet decreased significantly, b oth LH and FSH pituitary concentration and also basal gonadotropin plasma l evels in male rats. GnRH produced a significantly increment in LH secretion in both treated and control groups, reaching similar levels after stimulat ion. Nevertheless, the percentile increment from basal levels in the aprote ic group was almost four times the controls, suggesting an increased sensit ivity in pituitary response to GnRH in rats fed with AP diet. In female cas trated rats, the aproteic diet imposed 3 weeks after the surgery was unable to reduce basal gonadotropin secretion, and so also prolactin secretion. E stradiol/progesterone (EP) administration produced the activation of positi ve feedback mechanism, increasing significantly LH and FSH secretion in bot h controls and AP groups. Nevertheless, both gonadotropin responses to EP w ere significantly greater in rats fed with AP diet. Basal prolactin levels and response to EP were not different between both groups. This results sug gest that selective protein lack in a diet, reduced pituitary LH and FSH sy nthesis and secretion. This type of diet also increments pituitary sensitiv ity to GnRH administration in male rats, and gonadotropin response to posit ive feedback mechanism in female rats.