Thompson K, Coleman E S, Hudmon A, Kemppainen R J, Soyoola E O, Sartin J L
Department of Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, AL 36849-5520, USA.
Am J Vet Res. 1995 Sep;56(9):1228-31.
Excess production or long-term administration of glucocorticoids is detrimental to longitudinal growth in people and rats. A portion of this effect is attributed to cortisol inhibition of growth hormone (GH). Glucocorticoid effects are usually studied in subjects under long-term treatment with synthetic, more potent glucocorticoids, and, to the authors' knowledge, have not been examined in domestic animals. We sought to examine the effects of cortisol infusion on GH release in sheep. Cortisol infusion into castrated, male Suffolk sheep (1 to 1.5 years old) caused a significant (P < 0.0001) increase in cortisol concentration. Basal GH release was not affected over the 4-hour period of infusion. Growth hormone-releasing hormone administration stimulated GH release in both groups (P < 0.001); however, the control group had a greater response to growth hormone-releasing hormone than did the cortisol infused group (P < 0.0001). These results were duplicated in cultured sheep pituitary cells. Cortisol inhibition of GH release may be mediated via enhanced somatostatin release, owing to a direct inhibition of somatotrope function, or a combination of both mechanisms. Because of effects of stress and disease in increasing cortisol concentration, additional study of the mechanisms for cortisol inhibition of GH release in sheep needs to be performed.
糖皮质激素的过量产生或长期给药对人和大鼠的纵向生长有害。这种影响部分归因于皮质醇对生长激素（GH）的抑制作用。糖皮质激素的作用通常在长期接受合成的、效力更强的糖皮质激素治疗的受试者中进行研究，据作者所知，尚未在家畜中进行过研究。我们试图研究皮质醇输注对绵羊GH释放的影响。向去势的1至1.5岁雄性萨福克绵羊输注皮质醇导致皮质醇浓度显著升高（P < 0.0001）。在输注的4小时期间，基础GH释放未受影响。给予生长激素释放激素刺激了两组的GH释放（P < 0.001）；然而，对照组对生长激素释放激素的反应比皮质醇输注组更大（P < 0.0001）。这些结果在培养的绵羊垂体细胞中得到了重复。皮质醇对GH释放的抑制作用可能是通过增强生长抑素的释放介导的，这是由于对生长激素细胞功能的直接抑制，或两种机制的结合。由于应激和疾病会增加皮质醇浓度，因此需要对皮质醇抑制绵羊GH释放的机制进行进一步研究。
