INFLUENCE OF DIABETES ON THE GONADOTROPIN-RESPONSE TO THE NEGATIVE FEEDBACK EFFECT OF TESTOSTERONE AND HYPOTHALAMIC NEUROTRANSMITTER TURNOVER IN ADULT MALE-RATS

被引:18
作者
CHANDRASHEKAR, V
STEGER, RW
BARTKE, A
FADDEN, CT
KIENAST, SG
机构
[1] Department of Physiology, Southern Illinois University School of Medicine, Carbondale, IL
关键词
DIABETES; HYPOTHALAMUS; LUTEINIZING HORMONE; TESTOSTERONE; NEGATIVE FEEDBACK; NOREPINEPHRINE;
D O I
10.1159/000125847
中图分类号
R5 [内科学];
学科分类号
1002 ; 100201 ;
摘要
The influence of diabetes on the gonadotropin response to the negative feedback effect of testosterone (T) and hypothalamic neurotransmitter turnover rates in adult male rats was evaluated. Adult male Sprague-Dawley rats were made diabetic by an intraperitoneal injection of streptozotocin (STZ; 5 mg/100 g body weight) in citrate buffer. Vehicle-injected rats served as controls. On day 9, all rats were bilaterally castrated and treated subcutaneously on alternate days with either peanut oil or T propionate (TP) in peanut oil (100-mu-g/rat). Plasma follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), and T concentrations were measured by specific radioimmunoassays from blood samples collected on day 1 (before castration) and 2, 4, 6, and 7 days after castration. On day 7 after castration (day 15 after vehicle or STZ treatment), 1 h before autopsy, the rats were injected intraperitoneally with saline or a tyrosine hydroxylase inhibitor, alpha-methyl-p-tyrosine (25 mg/100 g BW), for the measurements of norepinephrine (NE) and dopamine turnover in median eminence and medial basal hypothalamus (MBH). Circulating FSH, LH, PRL, and T levels were significantly lower (FSH and T: p < 0.001; LH and PRL: p < 0.05) in gonad-intact rats treated with STZ than in vehicle-injected animals. The castration-induced increase in plasma LH levels was attenuated in diabetic rats. The suppressive effect of T on LH secretion was significantly greater (p < 0.001) in STZ-treated rats relative to TP-treated nondiabetic controls. Castration in both diabetic and nondiabetic rats increased (p < 0.001) FSH secretion, but these increases were not different until day 6 after castration, when plasma FSH levels in control rats significantly increased (p < 0.01), than in diabetic animals. In STZ-treated rats, the suppressive effect of TP on plasma FSH levels was significantly increased. The NE turnover rates in median eminence and MBH were significantly lower (p < 0.001) in castrated diabetic rats than in castrated controls. The MBH NE turnover was reduced after TP treatment in both subgroups, but the relative decline was much greater (p < 0.01) in diabetic rats. These results clearly indicate that induction of diabetes by STZ treatment reduces gonadotropin and PRL secretion and increases the sensitivity of the hypothalamic-pituitary axis to the negative feedback effect of T on gonadotropin secretion. The effect of diabetes on gonadotropin secretion in the adult male rat is probably due to the suppression of noradrenergic neuronal activity of the hypothalamus.
引用
收藏
页码:30 / 35
页数:6
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