Richardson S, Twente S, Audhya T
Department of Medicine, Veterans Administration Medical Center, New York, New York.
Am J Physiol. 1988 Dec;255(6 Pt 1):E829-32. doi: 10.1152/ajpendo.1988.255.6.E829.
The complex interactions of the hypothalamic releasing peptides somatostatin (SRIF) and growth hormone (GH)-releasing hormone (GHRF), which regulate GH secretion, are still incompletely understood. To further scrutinize these interactions, we have studied the effects of GHRF on SRIF secretion from dispersed adult rat hypothalamic cells. Rat GHRF caused calcium- and dose-dependent stimulation of SRIF release in static 1-h incubations. SRIF release was stimulated by GHRF in a concentration range of 1-100 nM. However, the extended dose-response curve was biphasic in nature, with a significantly lower SRIF response in the presence of 1 microM GHRF vs. 100 nM GHRF. SRIF release, stimulated by another secretagogue (10 microM veratridine), was not affected by the presence or absence of 1 microM GHRF, suggesting the lack of toxic impairment of hypothalamic cell function by GHRF at this concentration. In conclusion, a biphasic stimulatory pattern of SRIF secretion in response to GHRF was observed in experiments employing dispersed rat hypothalamic cells. The biphasic SRIF response pattern to GHRF may be relevant in the physiological regulation of GH secretion.
调节生长激素（GH）分泌的下丘脑释放肽——生长抑素（SRIF）和生长激素释放激素（GHRF）之间的复杂相互作用，目前仍未完全明确。为了进一步研究这些相互作用，我们研究了GHRF对成年大鼠下丘脑分散细胞分泌SRIF的影响。在1小时的静态孵育中，大鼠GHRF引起了钙依赖性和剂量依赖性的SRIF释放刺激。GHRF在1-100 nM的浓度范围内刺激SRIF释放。然而，扩展的剂量反应曲线本质上是双相的，与100 nM GHRF相比，在1 μM GHRF存在时SRIF反应显著降低。另一种促分泌素（10 μM藜芦碱）刺激的SRIF释放不受1 μM GHRF存在与否的影响，表明该浓度的GHRF对下丘脑细胞功能无毒性损害。总之，在使用大鼠下丘脑分散细胞的实验中，观察到SRIF分泌对GHRF的双相刺激模式。SRIF对GHRF的双相反应模式可能与GH分泌 的生理调节有关。
