Rat pancreatic islet function during prolonged glucose stimulation in vitro: Effect of sex and reproductive state

Prolonged stimulation with glucose may induce desensitisation of pancreatic beta-cell function in male rats. The effects of such a treatment on pancreatic islets of pregnant (P) rats, in which beta-cell function is enhanced, were studied in a perifusion design and compared with the effects on islets of cyclic female (C) and male (M) rats. The treatment induced in all three groups of islets a transient increase in both insulin and amylin secretion, followed by a gradual decline (desensitisation). Islets of P-rats released more insulin, but not amylin, than the other types of islets. Furthermore, desensitisation occurred later in islets of P-rats (after 2.5 h) than in islets of C- and M-rats (after 0.5 h) The amount of insulin, but not of amylin, stored in islets of P-rats was also much higher than in the islets of C- and M-rats. Glucagon release in all three groups of islets was suppressed during glucose stimulation, but tended to increase again after 3 h of continuous stimulation. It is concluded that the control of beta-cell function is similar in M- and C-rats, but is significantly altered in P-rats. It is suggested that desensitisation of the beta-cells is associated with desensitisation of the alpha-cells

SUPPRESSION BY LH-RELEASING HORMONE (LHRH) OF THE AUGMENTING EFFECT OF ESTRADIOL ON THE SECRETION OF LH AND FSH BY THE RAT PITUITARY-GLAND

Estradiol sensitizes the pituitary gland for the gonadotropin-releasing activity of LHRH. LHRH desensitizes the pituitary gland and does so in a dose-dependent manner. Moreover, LHRH dose-dependently suppresses the sensitizing effect of EB. In rats with an LHRH concentration in the plasma of about 90 pg/ml, the sensitizing effect of estradiol is absent