Zwain I, Gaillard J L, Dintinger T, Silberzahn P
Laboratoire de Biochimie, UA CNRS 609 Universite, Caen, France.
Biol Reprod. 1989 Mar;40(3):503-10. doi: 10.1095/biolreprod40.3.503.
A single i.m. injection of testosterone (750 mg of testosterone bexahydrobenzoate) or i.v. injection of human chorionic gonadotrophin (hCG) (10,000 IU) was given to geldings and stallions. Levels of unconjugated and conjugated (after solvolysis) androgens and estrogens were measured in blood and urine samples taken daily from the day of injection (D0) to the tenth day post-injection (D10). In the stallion, both treatments resulted in a sharp increase of plasma estrogens, which peaked one day before the androgen levels. Our results confirmed the testicular localization of a potent aromatase, which is able to aromatize androgens from endogenous as well as exogenous origin into conjugated estrogens. The very similar patterns of estrogen increase following testosterone or hCG administration suggest that the estrogen rise induced by hCG results at least partly from increased availability of testosterone. The abrupt drop in plasma estrogen levels cannot be explained by a lack of substrate, since two successive androgen injections did not succeed in maintaining the high estrogen levels. Since estrogens were unable to inhibit the aromatase activity in vitro, the drop in estrogen levels suggests a down-regulation of the aromatase synthesis.
对公马和去势雄马进行一次肌肉注射睾酮（750毫克环戊丙酸睾酮）或静脉注射人绒毛膜促性腺激素（hCG）（10,000国际单位）。从注射当天（D0）至注射后第十天（D10），每天采集血液和尿液样本，测定未结合和结合（溶剂解后）雄激素和雌激素的水平。在公马中，两种处理均导致血浆雌激素急剧增加，其峰值出现在雄激素水平达到峰值的前一天。我们的结果证实了一种强效芳香化酶的睾丸定位，该酶能够将内源性和外源性雄激素芳香化为结合雌激素。睾酮或hCG给药后雌激素增加的模式非常相似，这表明hCG诱导的雌激素升高至少部分是由于睾酮可用性增加所致。血浆雌激素水平的突然下降不能用底物缺乏来解释，因为连续两次注射雄激素未能维持高雌激素水平。由于雌激素在体外不能抑制芳香化酶活性，雌激素水平的下降表明芳香化酶合成的下调。
