Hudmon A, Davenport G, Coleman E S, Sartin J L
Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
Domest Anim Endocrinol. 2009 Oct;37(3):181-7. doi: 10.1016/j.domaniend.2009.05.004. Epub 2009 Jul 2.
Estradiol increases basal growth hormone (GH) concentrations in sheep and cattle. This study sought to determine the effects of estradiol on GH-releasing hormone (GRH)-stimulated GH release in sheep. Growth hormone secretory characteristics, the GH response to GRH, and steady-state GH mRNA concentrations were determined in castrated male lambs treated with 2 different doses of estradiol 17-beta for a 28-d experimental period. Although no differences between treatments in mean GH, basal GH, or GH pulse number were observed after 28 d of estradiol treatment, GH pulse amplitude was greater (P < 0.05) in the 2.00-cm implant-treated animals than in the control and 0.75-cm implant group. The effect of estradiol treatment on GRH-stimulated GH release revealed differences between the control and estradiol-treated animals (P < 0.05). The 15-min GH responses to 0.075 microg/kg hGRH in the control, 0.75-cm, and 2.00-cm implant groups, respectively, were 76 +/- 10, 22.6 +/- 2.1, and 43.6 +/- 15.0 ng/mL. Growth hormone mRNA content was determined for pituitary glands from the different treatment groups, and no differences in steady-state GH mRNA levels were observed. There were no differences in the mean plasma concentrations of IGF-I, cortisol, T(3), or T(4) from weekly samples. Growth hormone release from cultured ovine pituitary cells from control sheep was not affected by estradiol after 72 h or in a subsequent 3-h incubation with estradiol combined with GRH. These data suggest that estradiol has differing actions on basal and GRH-stimulated GH concentrations in plasma, but the increase in pulse amplitude does not represent an increased pituitary sensitivity to GRH.
雌二醇可提高绵羊和牛的基础生长激素（GH）浓度。本研究旨在确定雌二醇对绵羊中生长激素释放激素（GRH）刺激的GH释放的影响。在为期28天的实验期内，对用两种不同剂量的17-β雌二醇处理的去势雄性羔羊，测定其生长激素分泌特征、对GRH的GH反应以及稳态GH mRNA浓度。尽管在雌二醇处理28天后，各处理组之间在平均GH、基础GH或GH脉冲数上未观察到差异，但在植入2.00厘米的动物中，GH脉冲幅度比对照组和植入0.75厘米的组更大（P<0.05）。雌二醇处理对GRH刺激的GH释放的影响显示，对照组和雌二醇处理组动物之间存在差异（P<0.05）。对照组、植入0.75厘米和植入2.00厘米的组中，对0.075微克/千克hGRH的15分钟GH反应分别为76±10、22.6±2.1和43.6±15.0纳克/毫升。测定了不同处理组垂体的生长激素mRNA含量，未观察到稳态GH mRNA水平的差异。每周样本中IGF-I、皮质醇、T3或T4的平均血浆浓度没有差异。来自对照绵羊的培养绵羊垂体细胞的生长激素释放在72小时后或随后与雌二醇联合GRH孵育3小时后不受雌二醇影响。这些数据表明，雌二醇对血浆中基础和GRH刺激的GH浓度有不同作用，但脉冲幅度的增加并不代表垂体对GRH的敏感性增加。
