Lubbers L S, Hileman S M, Kuehl D E, Ferreira S A, Jackson G L
Department of Veterinary Biosciences, University of Illinois, Urbana-Champaign 61801, USA.
Domest Anim Endocrinol. 1998 Nov;15(6):511-24. doi: 10.1016/s0739-7240(98)00039-3.
We tested the hypothesis that rapidly expressed inhibitory effects of estradiol (E) on luteinizing hormone (LH) release in the male are attributable, in part, to suppression of luteinizing hormone-releasing hormone (LHRH) release. Hypophyseal-portal cannulated, castrated male sheep were infused with E (15 ng/kg/hr) or vehicle. Portal and jugular blood samples were collected at 10-min intervals for 4 hr before, and for either 12 hr (E, n = 4; vehicle, n = 4) or 24 hr (E, n = 8; vehicle, n = 3) after the start of infusion. In animals sampled for 16 hr, temporal changes in both LHRH and LH were assessed. In animals sampled for 28 hr, only LH data were analyzed. Before either the 12-hr or 24-hr infusion, LHRH and/or LH mean concentrations, pulse amplitude and interpulse interval (IPI) did not differ between E- and vehicle-infused animals. In animals sampled for 16 hr, no effects of time or steroid x time interactions were detected for mean LHRH and LHRH pulse amplitude; however, both were greater (P < 0.01) in vehicle-infused than in E-infused males. LHRH IPI was unaffected by infusion. In contrast, both mean LH and LH pulse amplitude declined (P < 0.01) within 4-8 hr after the start of E infusion, whereas mean LH IPI was unaffected. In animals sampled for 28 hr, an effect of time (P < 0.01) and a steroid x time interaction (P < 0.01) was detected for mean LH, and there was an effect of time (P < 0.01) on LH pulse amplitude. Mean LH IPI was not affected. Our results show that in male sheep E rapidly reduces LH release in the absence of a detectable change in LHRH release.
在雄性动物中，雌二醇（E）对促黄体生成素（LH）释放的快速抑制作用，部分归因于对促黄体生成素释放激素（LHRH）释放的抑制。对垂体门脉插管的去势雄性绵羊输注E（15纳克/千克/小时）或赋形剂。在输注开始前4小时，以及输注开始后12小时（E组，n = 4；赋形剂组，n = 4）或24小时（E组，n = 8；赋形剂组，n = 3），每隔10分钟采集一次垂体门脉和颈静脉血样。在采样16小时的动物中，评估LHRH和LH的时间变化。在采样28小时的动物中，仅分析LH数据。在12小时或24小时输注之前，输注E和输注赋形剂的动物之间，LHRH和/或LH的平均浓度、脉冲幅度和脉冲间期（IPI）没有差异。在采样16小时的动物中，未检测到时间或类固醇×时间相互作用对LHRH平均浓度和LHRH脉冲幅度的影响；然而，输注赋形剂的雄性动物的这两项指标均高于输注E的雄性动物（P < 0.01）。LHRH IPI不受输注影响。相比之下，在开始输注E后4 - 8小时内，LH平均浓度和LH脉冲幅度均下降（P < 0.01），而LH平均IPI不受影响。在采样28小时的动物中，检测到时间对LH平均浓度有影响（P < 0.01），以及类固醇×时间相互作用对LH平均浓度有影响（P < 0.01），并且时间对LH脉冲幅度有影响（P < 0.01）。LH平均IPI不受影响。我们的结果表明，在雄性绵羊中，E在未检测到LHRH释放有可察觉变化的情况下，迅速降低LH释放。
