Chase D J, Schanbacher B D, Lunstra D D
Developmental and Reproductive Biology, University of Michigan, Ann Arbor 48109.
Endocrinology. 1988 Aug;123(2):816-26. doi: 10.1210/endo-123-2-816.
Yearling rams actively immunized against GnRH were used as a hypogonadotropic model for studies of the significance of the pulsatility of LH secretion in determining the trophic actions of the hormone on testicular steroidogenesis. GnRH-immunized rams, in which testicular regression was complete, were infused iv for 12-20 days with ovine LH (NIDDK oLH 24) in three different regimens, delivering a total daily dose of 60 micrograms/100 kg: 1) 1-min pulses of 5 micrograms/100 kg every 2 h (low amplitude, high frequency), 2) 1-min pulses of 30 micrograms/100 kg every 12 h (high amplitude, low frequency), or 3) continuous infusion of 2.5 micrograms/100 kg.h. Serum testosterone levels and acute responses to LH challenges were monitored at intervals throughout the infusion periods. Acute responses to LH were evaluated in terms of the area under the curve for serum testosterone vs. time after LH and the lag time between the infusion of LH and attainment of maximum serum testosterone levels. At the beginning of the experiments, serum testosterone was at castrate values, and testosterone responses to LH were of low magnitude with a long lag time. LH infusion in the low amplitude, high frequency regimen consistently increased the magnitude and decreased the lag time of acute responses to LH; these effects were significant by the sixth day of treatment and persisted for the duration of the experiments. This regimen also had positive effects on morphological features of testes and Leydig cells. Infusion of the high amplitude, low frequency regimen, however, had neither of the positive effects on responsiveness to LH, but did seem to improve testicular and Leydig cell morphology. Continuous infusion of LH also increased the magnitude and decreased the lag time of responses to low amplitude pulses of LH, at least as well as the high frequency infusion regimen did. These results suggest that the high frequency, low amplitude pattern of LH secretion characteristic of reproductively active animals has trophic actions on the testes, increasing their responsiveness to acute gonadotropic stimulation, but the pulsatility of that pattern of LH secretion is not necessary for its trophic actions. The efficacy of high frequency LH secretion may depend only on the elevation of basal or mean LH concentrations, rather than on the low amplitude peaks or the dynamic changes in LH concentrations to which the testes are exposed.
一岁公羊被主动免疫促性腺激素释放激素（GnRH），作为低促性腺激素模型，用于研究促黄体生成素（LH）分泌的脉冲性在决定该激素对睾丸类固醇生成的营养作用中的意义。GnRH免疫的公羊，其睾丸萎缩已完全，通过三种不同方案静脉输注绵羊LH（美国国立糖尿病、消化和肾脏疾病研究所oLH 24）12 - 20天，每日总剂量为60微克/100千克：1）每2小时一次5微克/100千克的1分钟脉冲（低幅度，高频），2）每12小时一次30微克/100千克的1分钟脉冲（高幅度，低频），或3）以2.5微克/100千克·小时的速度持续输注。在整个输注期间定期监测血清睾酮水平以及对LH刺激的急性反应。根据血清睾酮与LH注射后时间的曲线下面积以及LH注射与血清睾酮达到最大水平之间的滞后时间来评估对LH的急性反应。在实验开始时，血清睾酮处于去势水平，对LH的睾酮反应幅度低且滞后时间长。低幅度、高频方案的LH输注持续增加对LH急性反应的幅度并缩短滞后时间；这些效应在治疗的第六天就很显著，并在实验期间持续存在。该方案对睾丸和莱迪希细胞的形态特征也有积极影响。然而，高幅度、低频方案的输注对LH反应性没有任何积极影响，但似乎确实改善了睾丸和莱迪希细胞的形态。持续输注LH也增加了对低幅度LH脉冲反应的幅度并缩短了滞后时间，至少与高频输注方案一样有效。这些结果表明，生殖活跃动物特有的高频、低幅度LH分泌模式对睾丸具有营养作用，增加了它们对急性促性腺激素刺激的反应性，但该LH分泌模式的脉冲性对于其营养作用并非必需。高频LH分泌的功效可能仅取决于基础或平均LH浓度的升高，而不是取决于低幅度峰值或睾丸所暴露的LH浓度的动态变化。
