Chung C S, Etherton T D
Endocrinology. 1986 Aug;119(2):780-6. doi: 10.1210/endo-119-2-780.
The effect that GH has on regulating GH binding to its receptors has not been resolved. This report describes the characterization of porcine (p) GH binding to pig liver membranes and clarifies the issue of regulation of GH binding by measuring pGH binding to liver membranes prepared from pigs treated daily for 35 days with different doses of pGH (0, 10, 30, or 70 micrograms/kg BW). Specific binding of [125I]pGH was dependent on time, pH, and membrane protein concentration. At 23 C, pGH binding reached a steady state after 24 h. Maximal pGH binding was observed at pH 7. Binding increased linearly as membrane protein concentration was increased from 150 to 450 micrograms/tube. Specificity studies indicated that the hepatic GH receptor was somatogenic, since porcine PRL poorly inhibited [125I] pGH binding (cross-reactivity, 0.1%). Treatment of microsomes from control pigs with 4 m MgCl2 to remove endogenously bound pGH did not affect pGH binding, whereas binding was significantly increased to microsomes from pGH-treated pigs. Binding of pGH increased in a linear manner with the dose of pGH given for 35 days (r = 0.79), thus establishing the inductive effect of chronic pGH administration on pGH binding in pig liver. GH binding was highly correlated with weight gain in pigs treated with pGH (r = 0.76). In addition, the serum insulin-like growth factor I (IGF-I) concentration was increased linearly (r = 0.87) by pGH. This increase in serum IGF-I was also highly correlated with the increase in pGH binding (r = 0.71). These results suggest that hepatic GH binding plays an important role in regulating pig growth, which may be mediated, in part, by an increase in hepatic IGF-I synthesis and secretion. The present report is also the first to establish that exogenous pGH induces pGH binding to pig hepatic GH receptors and to relate this increase in binding to an enhancement in pig growth.
生长激素（GH）对调节其与受体结合的作用尚未明确。本报告描述了猪生长激素（pGH）与猪肝细胞膜结合的特性，并通过测量pGH与用不同剂量的pGH（0、10、30或70微克/千克体重）每日处理35天的猪所制备的肝细胞膜的结合情况，阐明了GH结合的调节问题。[125I]pGH的特异性结合取决于时间、pH值和膜蛋白浓度。在23℃下，pGH结合在24小时后达到稳态。在pH 7时观察到最大pGH结合。随着膜蛋白浓度从150微克/管增加到450微克/管，结合呈线性增加。特异性研究表明，肝脏GH受体具有促生长作用，因为猪催乳素（PRL）对[125I]pGH结合的抑制作用较弱（交叉反应性为0.1%）。用4 mM MgCl2处理对照猪的微粒体以去除内源性结合的pGH并不影响pGH结合，而pGH处理猪的微粒体结合则显著增加。pGH的结合随着35天给予的pGH剂量呈线性增加（r = 0.79），从而确定了长期给予pGH对猪肝中pGH结合的诱导作用。在接受pGH治疗的猪中，GH结合与体重增加高度相关（r = 0.76）。此外，pGH使血清胰岛素样生长因子I（IGF-I）浓度呈线性增加（r = 0.87）。血清IGF-I的这种增加也与pGH结合的增加高度相关（r = 0.71）。这些结果表明，肝脏GH结合在调节猪的生长中起重要作用，这可能部分是由肝脏IGF-I合成和分泌的增加介导的。本报告也是首次证实外源性pGH诱导pGH与猪肝脏GH受体结合，并将这种结合增加与猪生长的增强联系起来。
