Dubreuil P, Pelletier G, Couture Y, Lapierre H, Petitclerc D, Morisset J, Gaudreau P, Brazeau P
Department of Biology, Univ. Sherbrooke, QC, Canada.
Domest Anim Endocrinol. 1989 Jan;6(1):15-24. doi: 10.1016/0739-7240(89)90003-9.
Growth hormone (GH) release is influenced mainly by two hypothalamic factors, growth hormone-releasing factor (GRF) and somatostatin and is modulated by other hormones such as gonadal steroids. The objective of this study was to determine if castration (CA) and exogenous testosterone (TE) affect endogenous and GRF-induced GH release. Purebred Yorkshire male pigs (n = 32) were assigned to one of the following treatments: T1:CA; T2:CA +/- TE; T3: intact (IN); T4: IN +/- TE, in a 2 x 2 factorial design. Piglets were castrated at 3 days of age. Testosterone propionate (1.0 mg/kg) in sesame oil (2 ml) or sesame oil alone was injected sc SID during a 10-day period before each sampling day at 9, 15 and 21 weeks of age. Jugular blood samples were collected for a 6-hr period preceding and following iv injection of hGRF (1-29)NH2 (10 micrograms/kg). These procedures were repeated at 9, 15 and 21 weeks of age. The overall mean GH levels and the area under the GH peaks before and after GRF stimulation were lower (P less than .05) in castrated animals than in intact animals. Testosterone treatment increased (P less than .05) circulating TE levels and increased the amplitude of the endogenous GH peaks but did not affect (P greater than .05) the GRF-induced GH release. Increasing age produced a marked reduction of the amplitude of the GH peaks, the area under the GH peaks, the baseline mean and the overall mean GH levels during the 6-hr period preceding GRF injection. The present data support the hypothesis that castration in pigs reduces circulating and GRF-induced GH release. Exogenous testosterone for 10 days did not stimulate endogenous or GRF-induced GH release with the exception of the amplitude of the endogenous GH peaks.
生长激素（GH）的释放主要受两种下丘脑因子，即生长激素释放因子（GRF）和生长抑素的影响，并受其他激素如性腺类固醇的调节。本研究的目的是确定去势（CA）和外源性睾酮（TE）是否影响内源性和GRF诱导的GH释放。将纯种约克夏雄性仔猪（n = 32）按照2×2析因设计分为以下处理组之一：T1：去势；T2：去势+/- TE；T3：完整（IN）；T4：完整+/- TE。仔猪在3日龄时去势。在9、15和21周龄的每个采样日前10天期间，每天一次皮下注射芝麻油（2 ml）中含丙酸睾酮（1.0 mg/kg）或仅注射芝麻油。在静脉注射hGRF（1-29）NH2（10微克/千克）前后6小时内采集颈静脉血样。这些程序在9、15和21周龄时重复进行。去势动物中，GRF刺激前后的总体平均GH水平和GH峰值下的面积低于（P <.05）完整动物。睾酮处理增加了（P <.05）循环TE水平，并增加了内源性GH峰值的幅度，但不影响（P>.05）GRF诱导的GH释放。随着年龄增长，GRF注射前6小时期间GH峰值的幅度、GH峰值下的面积、基线平均值和总体平均GH水平显著降低。目前的数据支持以下假设：猪去势会降低循环和GRF诱导的GH释放。除了内源性GH峰值的幅度外，外源性睾酮处理10天并未刺激内源性或GRF诱导的GH释放。
