Richardson S B, Twente S
Research Program, Veterans Administration, Medical Center, New York, New York 10010.
Endocrinology. 1990 Feb;126(2):1043-6. doi: 10.1210/endo-126-2-1043.
A number of in vivo studies suggest that hypothalamic somatostatin (SRIF) tone is stimulated by the beta-adrenergic system. Employing dispersed adult male rat hypothalamic cells, we studied the effects of beta-adrenergic antagonists on the release of hypothalamic SRIF. Propranolol, at concentrations of 1-100 microM, had no detectable effect on basal SRIF release, but caused dose-dependent inhibition of SRIF release stimulated by ouabain. Two other beta-adrenergic antagonists, labetolol and metoprolol, also caused inhibition of ouabain-stimulated SRIF release. The alpha 2-agonist clonidine was without effect on SRIF release under basal or stimulated conditions. GH secretion from monolayers of dispersed rat anterior pituitary cells was also examined. Propranolol (1-100 microM) had no significant effect on basal GH secretion or GH secretion stimulated by rat GRF. In conclusion, 1) beta-adrenergic antagonists caused inhibition of stimulated SRIF release; 2) clonidine had no detectable effect on SRIF release; and 3) propranolol did not affect GH secretion in vitro. These findings support the hypothesis that beta-adrenergic antagonists augment GH responsivity by inhibiting hypothalamic SRIF release.
多项体内研究表明，β-肾上腺素能系统可刺激下丘脑生长抑素（SRIF）分泌。我们利用成年雄性大鼠下丘脑分散细胞，研究了β-肾上腺素能拮抗剂对下丘脑SRIF释放的影响。普萘洛尔在浓度为1-100微摩尔时，对基础SRIF释放无明显影响，但可剂量依赖性抑制哇巴因刺激的SRIF释放。另外两种β-肾上腺素能拮抗剂拉贝洛尔和美托洛尔也可抑制哇巴因刺激的SRIF释放。α2-激动剂可乐定在基础或刺激条件下对SRIF释放均无影响。我们还检测了大鼠垂体前叶分散细胞单层的生长激素（GH）分泌。普萘洛尔（1-100微摩尔）对基础GH分泌或大鼠生长激素释放因子（GRF）刺激的GH分泌均无显著影响。总之，1）β-肾上腺素能拮抗剂可抑制刺激后的SRIF释放；2）可乐定对SRIF释放无明显影响；3）普萘洛尔在体外不影响GH分泌。这些发现支持了β-肾上腺素能拮抗剂通过抑制下丘脑SRIF释放来增强GH反应性的假说。
