Klindt J, Buonomo F C, Wise T, Yen J T
U.S. Department of Agriculture-Animal Research Service, Roman L. Hruska U.S. Meat Animal Research Center, Clay Center, Nebraska 68933, USA.
Endocrinology. 1996 Sep;137(9):3689-95. doi: 10.1210/endo.137.9.8756534.
The effects of long term administration of GH on serum concentrations of hormones and metabolites was investigated in intact and castrate male swine. At 10 weeks of age, male swine were assigned to six treatments (n = 10/group): nonimplanted intact and castrate males; intact males implanted for 6 weeks, from 22-28 weeks of age; intact males implanted for 12 weeks, from 16-28 weeks of age; and intact and castrate males implanted for 18 weeks, from 10-28 weeks of age. Recombinant porcine GH was administered with sustained release implants designed to deliver a dose of 4 mg/day for 6 weeks. Throughout the study, blood samples were collected, and serum was harvested to quantitate circulating concentrations of glucose, urea nitrogen, GH, insulin, insulin-like growth factor I (IGF-I), IGF-II, and PRL. The pattern of administered GH in the serum suggests that the presence of testes and prior treatment with GH influence GH clearance. Somatotropin treatment elevated serum concentrations of GH and increased serum levels of glucose, insulin, IGF-I, and IGF-II in both intact and castrate animals. However, during the prepubertal period of 10-16 weeks, GH-treated intact males were resistant to the diabetogenic actions of GH, whereas significantly increased serum levels of glucose and insulin occurred in GH-treated castrates during this period. Changes in serum levels of IGF-I throughout the study and in insulin after the first 6 weeks followed the pattern of circulating GH concentrations in the treated animals. Serum concentrations of IGF-II were increased after GH administration, but, in contrast to the IGF-I response, IGF-II levels remained elevated as GH concentrations waned in the latter portion of the implant period. The maintenance of higher serum levels of IGF-II may be less dependent upon GH than are insulin and IGF-I. Administration of GH to intact males is more efficacious in altering metabolites and hormones, with the exception of IGF-I, during the peripubertal and postpubertal periods than during the prepubertal period.
在完整和去势雄性猪中研究了长期施用生长激素（GH）对血清激素和代谢物浓度的影响。10周龄时，将雄性猪分为六种处理组（每组n = 10）：未植入的完整和去势雄性；22至28周龄植入6周的完整雄性；16至28周龄植入12周的完整雄性；以及10至28周龄植入18周的完整和去势雄性。使用设计为以4毫克/天的剂量持续释放6周的植入物给予重组猪生长激素。在整个研究过程中，采集血样并收集血清，以定量循环中的葡萄糖、尿素氮、生长激素、胰岛素、胰岛素样生长因子I（IGF-I）、IGF-II和催乳素（PRL）的浓度。血清中施用的生长激素模式表明，睾丸的存在和先前生长激素治疗会影响生长激素清除率。生长激素治疗提高了完整和去势动物血清生长激素浓度，并增加了血清葡萄糖、胰岛素、IGF-I和IGF-II水平。然而，在10至16周的青春期前阶段，接受生长激素治疗的完整雄性对生长激素的致糖尿病作用具有抗性，而在此期间接受生长激素治疗的去势动物血清葡萄糖和胰岛素水平显著升高。在整个研究过程中，IGF-I血清水平的变化以及前6周后胰岛素的变化遵循治疗动物中循环生长激素浓度的模式。生长激素给药后，IGF-II血清浓度升高，但与IGF-I反应不同的是，在植入期后期生长激素浓度下降时，IGF-II水平仍保持升高。与胰岛素和IGF-I相比，维持较高的血清IGF-II水平可能对生长激素的依赖性较小。在青春期和青春期后阶段，向完整雄性施用生长激素在改变代谢物和激素（IGF-I除外）方面比青春期前阶段更有效。
