Fishman A, Hertz P, Hochberg Z
Department of Pharmacology, Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa.
Neuroendocrinology. 1993 May;57(5):782-8. doi: 10.1159/000126437.
The aims of the present study were to investigate the sexual dimorphism and the role of sex steroids in GH secretion at the pituitary level, and to evaluate the ontogenesis of these effects. Towards these aims we used an in vitro perifusion system of hemipituitaries under a simulated milieu of hypothalamic factors: two 3-min pulses of GHRH at 3-hour intervals were separated by continuous flow of somatostatin. Rat GH was measured in 2.4-min fractions and analyzed by the pulse analysis program PULSAR. Pulses were similar in prepubertal male and female rats, but sexual dimorphism was evident in adults. In adult males, who had undergone neonatal gonadectomy, GH pulse amplitude and area under the curve (AUC) were lower compared to control. When gonadectomy had been performed at a prepubertal age, the pulse amplitude was still lower, but the AUC was not different from control. The gap between orchiectomy at neonatal and prepubertal age indicates the perinatal imprint, which induces an increase in AUC. Neonatal testosterone treatment of intact female rats had no effect on GH secretion by adult pituitaries. In neonatally gonadectomized female rats, under neonatal testosterone treatment, the pulse amplitude increased. A similar increase was observed after neonatal gonadectomy without testosterone treatment. We conclude that the sexual dimorphism of GH secretion is partially induced at the pituitary level and its response to the hypothalamic hormones. We assume that a neonatal imprint effect of testosterone in the male induces primarily an increase in AUC in response to GHRH. The imprint in females influences the GH pulse amplitude and AUC.
本研究的目的是调查生长激素（GH）分泌在垂体水平上的性别差异以及性类固醇的作用，并评估这些作用的个体发生过程。为实现这些目标，我们使用了半垂体体外灌流系统，该系统处于模拟的下丘脑因子环境中：每隔3小时给予两次3分钟的生长激素释放激素（GHRH）脉冲，两次脉冲之间为生长抑素的持续灌流。每隔2.4分钟收集一次大鼠GH样本，并通过脉冲分析程序PULSAR进行分析。青春期前的雄性和雌性大鼠的脉冲相似，但成年大鼠中存在明显的性别差异。成年雄性大鼠若在新生期进行性腺切除术，其GH脉冲幅度和曲线下面积（AUC）均低于对照组。若在青春期前进行性腺切除术，脉冲幅度仍然较低，但AUC与对照组无差异。新生期和青春期前睾丸切除术之间的差距表明围产期印记会导致AUC增加。对完整雌性大鼠进行新生期睾酮处理，对成年垂体的GH分泌没有影响。在新生期进行性腺切除的雌性大鼠中，给予新生期睾酮处理后，脉冲幅度增加。在未进行睾酮处理的新生期性腺切除后也观察到了类似的增加。我们得出结论，GH分泌的性别差异部分是在垂体水平及其对下丘脑激素的反应中诱导产生的。我们推测，雄性大鼠中睾酮的新生期印记效应主要导致对GHRH反应的AUC增加。雌性大鼠中的印记影响GH脉冲幅度和AUC。
