Garza F, Thompson D L, St George R L, Reville-Moroz S I
J Anim Sci. 1985 Jul;61(1):240-4. doi: 10.2527/jas1985.611240x.
Eight long-term ovariectomized pony mares were treated with either dihydrotestosterone (DHT) benzoate (400 micrograms/kg body weight) in safflower oil or an equivalent amount of oil every other day for 21 d to determine the effects of DHT on follicle stimulating hormone (FSH) and luteinizing hormone (LH) concentrations in blood samples drawn once daily and after administration of three successive injections of gonadotropin releasing hormone (GnRH). The GnRH injections were given at 4-h intervals on the day following the last DHT or oil injection. Treatment with DHT benzoate did not alter (P greater than .10) concentrations of FSH or LH in daily blood samples relative to controls. The FSH and LH response, assessed by areas under the GnRH curves, decreased (P less than .05) from the first to third injection of GnRH when averaged over both groups of mares. There was no effect of DHT treatment on FSH response to GnRH. There was an interaction (P less than .05) between treatment and GnRH injection for LH areas; areas decreased (P less than .05) for DHT-treated mares from the first to third GnRH injection but were unchanged for control mares. It seems that DHT alone cannot mimic the stimulatory effects of testosterone on FSH production and secretion as observed in previous experiments with ovariectomized and intact mares. Moreover, because intact mares have been shown previously to respond to DHT treatment with an increase in GnRH-induced FSH secretion, it appears that some mechanism is lost in long-term ovariectomized mares, making them unresponsive to DHT treatment.
八匹长期卵巢切除的母马，每隔一天分别接受红花油中苯甲酸二氢睾酮（DHT）（400微克/千克体重）或等量油剂的治疗，持续21天，以确定DHT对每日采集的血样中促卵泡激素（FSH）和促黄体生成素（LH）浓度的影响，以及在连续三次注射促性腺激素释放激素（GnRH）后的影响。GnRH注射在最后一次DHT或油剂注射后的第二天，每隔4小时进行一次。与对照组相比，苯甲酸二氢睾酮治疗并未改变（P>0.10）每日血样中FSH或LH的浓度。当对两组母马的平均值进行评估时，通过GnRH曲线下面积评估的FSH和LH反应从第一次到第三次GnRH注射时下降（P<0.05）。DHT治疗对GnRH刺激的FSH反应没有影响。对于LH面积，治疗和GnRH注射之间存在交互作用（P<0.05）；DHT处理的母马从第一次到第三次GnRH注射时面积下降（P<0.05），而对照母马则无变化。似乎单独使用DHT不能模拟睾酮对FSH产生和分泌的刺激作用，这与之前对卵巢切除和未切除卵巢的母马所做的实验结果一致。此外，由于之前已表明未切除卵巢的母马对DHT治疗的反应是GnRH诱导的FSH分泌增加，因此似乎长期卵巢切除的母马失去了某种机制，使其对DHT治疗无反应。
