Winters S J, Medhamurthy R, Gay V L, Plant T M
Department of Medicine, University of Pittsburgh School of Medicine, Pennsylvania.
Endocrinology. 1991 Oct;129(4):1755-61. doi: 10.1210/endo-129-4-1755.
The secretion of inhibin by the testis was studied in the rhesus monkey, a species which exhibits marked episodic and diurnal patterns of testosterone (T) secretion. Inhibin and T were measured by RIA in blood samples drawn every 20 min for 24 h from 5 adult male monkeys. The molecular size of circulating inhibin, estimated by gel chromatography, was approximately 31 kDA. Plasma inhibin levels were undetectable in long term castrates. T was secreted episodically at a frequency of 6.0 +/- 0.9 pulses/24 h. The computer algorithm also identified 4.6 +/- 0.8 inhibin pulses/24 h. Of 30 T pulses among the 5 animals, however, only 7 coincided with low amplitude inhibin secretory bursts. Each animal demonstrated a significant diurnal periodicity in T secretion, with mean maximum concentrations at 0108 h (range, 2100-0640 h). By contrast, there was no significant diurnal rhythm for inhibin in any of the animals. The pulsatile administration of GnRH (0.1 micrograms/min, iv, for 3 min every 3 h) was used to activate the pituitary testicular axis in 6 juvenile monkeys. After 5 weeks of GnRH priming, a pulse of GnRH produced an immediate 4-fold rise in serum LH concentrations, followed within 30-50 min by a 5-fold increase in circulating T levels. FSH levels rose 50%. During the 3-h GnRH interpulse interval, however, there was no change in serum inhibin levels. Two GnRH-treated juvenile monkeys underwent bilateral orchidectomy. In each animal, circulating inhibin levels declined rapidly, with estimated first phase half-lives of 23 and 32 min, respectively. In conclusion, circulating inhibin concentrations in male rhesus monkeys exhibit neither the prominent moment to moment changes nor the circadian pattern characteristic of T secretion in this species. The relatively constant inhibin levels cannot be explained by prolonged metabolic clearance. The data are consistent with the proposal that most of the inhibin in the circulation is released across the apical surface of Sertoli cells into the seminiferous tubular fluid with passage into the rete testis from which it is continuously absorbed. The intermittent LH signal, by contrast, appears to make a minor contribution to the release of inhibin from the primate testis into the circulation.
在恒河猴（一种呈现出明显的睾酮（T）分泌的间歇性和昼夜模式的物种）中研究了睾丸抑制素的分泌。从5只成年雄性猴子身上，每20分钟采集一次血样，共采集24小时，用放射免疫分析法（RIA）测定抑制素和T。通过凝胶色谱法估计，循环抑制素的分子大小约为31 kDa。长期去势的猴子血浆中检测不到抑制素水平。T以6.0±0.9次脉冲/24小时的频率间歇性分泌。计算机算法还识别出4.6±0.8次抑制素脉冲/24小时。然而，在这5只动物的30次T脉冲中，只有7次与低幅度的抑制素分泌爆发同时发生。每只动物的T分泌都表现出显著的昼夜周期性，平均最高浓度出现在0108时（范围为2100 - 0640时）。相比之下，任何一只动物的抑制素都没有明显的昼夜节律。对6只幼年猴子采用GnRH脉冲给药（0.1微克/分钟，静脉注射，每3小时注射3分钟）来激活垂体 - 睾丸轴。GnRH预刺激5周后，一次GnRH脉冲使血清LH浓度立即升高4倍，随后在30 - 50分钟内循环T水平升高5倍。FSH水平升高50%。然而，在3小时的GnRH脉冲间期，血清抑制素水平没有变化。对2只接受GnRH治疗的幼年猴子进行了双侧睾丸切除术。在每只动物中，循环抑制素水平迅速下降，估计第一阶段半衰期分别为23分钟和32分钟。总之，雄性恒河猴循环中的抑制素浓度既没有该物种中T分泌所特有的显著的瞬间变化，也没有昼夜模式。抑制素水平相对恒定无法用代谢清除时间延长来解释。这些数据与以下观点一致：循环中的大部分抑制素是通过支持细胞的顶端表面释放到生精小管液中，然后进入睾丸网，再从那里被持续吸收。相比之下，间歇性的LH信号似乎对灵长类动物睾丸中抑制素释放到循环中的贡献较小。
