Schlatt Stefan, Pohl Clifford R, Ehmcke Jens, Ramaswamy Suresh
Department of Cell Biology and Physiology, Center for Research in Reproductive Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA.
Biol Reprod. 2008 Jul;79(1):93-9. doi: 10.1095/biolreprod.107.066126. Epub 2008 Mar 26.
Testosterone shows circadian rhythms in monkeys with low serum levels in the morning hours. The decline relies on a diminished frequency of LH pulses. Inhibin B shows no diurnal patterns. In elderly men, the diurnal rhythm of testosterone is blunted and inhibin levels fall. Here we explore whether aging exerts similar effects in the rhesus monkey. We collected blood samples from groups of young (6-9 yr) and old (12-16 yr) male rhesus monkeys at 20-min intervals for a period of 24 h under remote sampling via a venous catheter. We determined moment-to-moment changes in plasma levels of testosterone, FSH, and LH by RIA, and of inhibin B by ELISA. We found significant diurnal patterns of testosterone in both groups. The circadian rhythm in testosterone was enhanced in older monkeys. Testosterone levels and pulse frequencies dropped significantly below those of young monkeys during midday hours. Diminished pulse frequency of LH appeared to be responsible for the midday testosterone decrease in old monkeys, while LH and testosterone pulse frequency did not change in young monkeys at corresponding time points. Old monkeys showed extended periods of LH-pulse quiescence in the morning and midday hours. Inhibin B and FSH levels were generally lower in old monkeys compared with the young group, but neither inhibin B nor FSH showed circadian rhythms. We conclude from these data that old rhesus monkeys have a more prominent circadian rhythm of LH and testosterone resulting from an extended midday period of quiescence in the hypothalamus-pituitary-gonadal axis.
睾酮在猴子体内呈现昼夜节律，清晨血清水平较低。这种下降依赖于促黄体生成素（LH）脉冲频率的降低。抑制素B没有昼夜变化模式。在老年男性中，睾酮的昼夜节律变钝，抑制素水平下降。在此，我们探讨衰老在恒河猴身上是否有类似影响。我们通过静脉导管远程采样，以20分钟的间隔，在24小时内从年轻（6 - 9岁）和年老（12 - 16岁）雄性恒河猴组采集血样。我们通过放射免疫分析法（RIA）测定睾酮、促卵泡生成素（FSH）和LH的血浆水平的即时变化，通过酶联免疫吸附测定法（ELISA）测定抑制素B的血浆水平的即时变化。我们发现两组中睾酮均有显著的昼夜变化模式。老年猴子中睾酮的昼夜节律增强。在中午时段，睾酮水平和脉冲频率显著低于年轻猴子。老年猴子中午睾酮水平下降似乎是由于LH脉冲频率降低，而在相应时间点年轻猴子的LH和睾酮脉冲频率没有变化。老年猴子在早晨和中午时段LH脉冲静止期延长。与年轻组相比，老年猴子的抑制素B和FSH水平总体较低，但抑制素B和FSH均未显示昼夜节律。从这些数据我们得出结论，老年恒河猴下丘脑 - 垂体 - 性腺轴中午静止期延长，导致LH和睾酮的昼夜节律更显著。
