Plouzek C A, Trenkle A
Department of Animal Science, Iowa State University, Ames 50011.
Domest Anim Endocrinol. 1991 Jan;8(1):63-72. doi: 10.1016/0739-7240(91)90040-q.
Plasma Growth hormone (GH) profiles, secretion rates (SR), metabolic clearance rates (MCR) of intravenously infused GH, and response to 0.0165, 0.067, and 0.267 microgram of growth hormone-releasing factor (GHRF)/kg body weight (bwt) were studied in intact and castrated male and female cattle (4 of each) at 5, 8, 12, and 15 mo of age. As cattle aged, overall GH levels in the plasma decreased (P less than .01), GH baseline concentrations declined (P less than .05), SR decreased (P less than .01), half-life of GH decreased (P less than .01), and the GH response to intravenous injections of GHRF declined (P less than .05). Bulls had elevated overall and baseline GH concentrations (P less than .05), greater amplitude and number of GH secretory periods (P less than .01), and greater SR (P less than .05) than steers, heifers, or ovariectomized heifers. Males had more frequent GH spikes and secretory periods of higher amplitudes, greater SR, and greater GH responses to 0.0165 microgram GHRF kg bwt (P less than .05) than females. Castration had no impact on the GH status of heifers. It is suggested that testosterone or its metabolites enhanced GH secretion in bulls.
对5、8、12和15月龄的完整及阉割的雄性和雌性牛（每种4头），研究了血浆生长激素（GH）水平、分泌率（SR）、静脉注射GH的代谢清除率（MCR）以及对0.0165、0.067和0.267微克生长激素释放因子（GHRF）/千克体重（bwt）的反应。随着牛年龄增长，血浆中总体GH水平下降（P<0.01），GH基线浓度降低（P<0.05），SR下降（P<0.01），GH半衰期缩短（P<0.01），且对静脉注射GHRF的GH反应下降（P<0.05）。公牛的总体和基线GH浓度升高（P<0.05），GH分泌期的幅度和次数更多（P<0.01），且SR比阉牛、小母牛或去卵巢小母牛更高（P<0.05）。雄性比雌性有更频繁的GH峰值和更高幅度的分泌期，SR更高，对0.0165微克GHRF/kg bwt的GH反应更大（P<0.05）。阉割对小母牛的GH状态没有影响。提示睾酮或其代谢产物增强了公牛的GH分泌。
