Tang Y P, Sisk C L
Department of Psychology, Michigan State University, East Lansing 48824.
J Endocrinol. 1988 Jun;117(3):461-6. doi: 10.1677/joe.0.1170461.
The biological activity of testosterone often depends on the conversion of testosterone within the target cell to an androgenic or oestrogenic metabolite. The purpose of this study was to compare the relative ability of testosterone and two of its metabolites, dihydrotestosterone (DHT) and oestradiol, to suppress LH secretion in castrated male ferrets. Castrated ferrets were treated with five different doses of steroid by implanting various numbers of s.c. silicone elastomer capsules packed with either testosterone, DHT or oestradiol. The lowest dose of oestradiol (0.1 mm capsule length/100 g body weight, mean estimated total release rate of 25 ng/day) significantly suppressed plasma concentrations of LH in castrated ferrets. Higher amounts of DHT (2.5 mm capsule length/100 g body weight, mean estimated total release rate of 88 ng/day) were required for a significant reduction in plasma concentrations of LH. Concentrations of LH were also significantly lowered by testosterone when administered at a 2.5 mm capsule length/100 g body weight; however, estimated total release rate was 312 ng/day from these capsules. The fact that oestradiol was more effective than DHT, and that DHT was more effective than testosterone in inhibiting LH secretion in castrated ferrets, suggests that in gonadally intact ferrets, testosterone may be converted to DHT or oestradiol within target cells that mediate steroid negative feedback on LH secretion.
睾酮的生物活性通常取决于其在靶细胞内转化为雄激素或雌激素代谢物。本研究的目的是比较睾酮及其两种代谢物，即双氢睾酮（DHT）和雌二醇，在去势雄性雪貂中抑制促黄体生成素（LH）分泌的相对能力。通过植入不同数量皮下填充睾酮、DHT或雌二醇的硅胶弹性体胶囊，对去势雪貂用五种不同剂量的类固醇进行治疗。最低剂量的雌二醇（0.1毫米胶囊长度/100克体重，平均估计总释放率为25纳克/天）可显著抑制去势雪貂血浆中LH的浓度。需要更高剂量的DHT（2.5毫米胶囊长度/100克体重，平均估计总释放率为88纳克/天）才能使血浆中LH浓度显著降低。当以2.5毫米胶囊长度/100克体重给药时，睾酮也可显著降低LH的浓度；然而，这些胶囊的估计总释放率为312纳克/天。在去势雪貂中，雌二醇比DHT更有效，DHT比睾酮更有效地抑制LH分泌，这一事实表明，在性腺完整的雪貂中，睾酮可能在介导对LH分泌的类固醇负反馈的靶细胞内转化为DHT或雌二醇。
