Jetton A E, Turek F W, Schwartz N B
Department of Neurobiology and Physiology, Northwestern University, Evanston, Ill.
Neuroendocrinology. 1994 Nov;60(5):527-34. doi: 10.1159/000126790.
Melatonin, a pineal hormone, is known to play an important role in mediating changes in the reproductive system which occur in response to seasonal changes in the length of the day. An in vitro pituitary perifusion system has been used to examine both direct and indirect effects of melatonin on pituitary gonadotropin basal secretion and responsiveness to GnRH stimulation. Anterior pituitaries from adult male golden hamsters were perifused with an APS 10 perifusion system for 6 h. Both basal secretion and secretion in response to hourly GnRH stimulation (1 min, 35 ng/ml pulses) were evaluated for LH and FSH. In order to expose pituitaries to shorter and longer durations of melatonin, tissue was perifused with melatonin-containing medium following dissection in the daytime (when endogenous melatonin levels are low) and following dissection in the nighttime (when endogenous melatonin levels are high). Exposure of pituitary tissue from golden hamsters to melatonin during perifusion caused a decrease in basal secretion of LH but did not affect GnRH stimulated LH or FSH release regardless of the time of dissection. There was, however, an effect of some diurnal factor to lower FSH responsiveness to GnRH stimulation from tissue dissected in the nighttime. It is suggested that melatonin may be responsible for this diurnal difference. Therefore, melatonin can act directly at the anterior pituitary to lower basal LH secretion, and melatonin or some other diurnal factor can act in vivo to lower pituitary FSH secretion in response to GnRH stimulation during the night.
褪黑素是一种松果体激素，已知在介导生殖系统随白昼长度季节性变化而发生的改变中发挥重要作用。已使用体外垂体灌流系统来研究褪黑素对垂体促性腺激素基础分泌以及对促性腺激素释放激素（GnRH）刺激反应性的直接和间接影响。用APS 10灌流系统对成年雄性金黄仓鼠的垂体前叶进行6小时灌流。评估了促黄体生成素（LH）和促卵泡生成素（FSH）的基础分泌以及对每小时一次GnRH刺激（1分钟，35纳克/毫升脉冲）的分泌情况。为了使垂体暴露于不同时长的褪黑素中，在白天（内源性褪黑素水平较低时）解剖后以及夜间（内源性褪黑素水平较高时）解剖后，用含褪黑素的培养基对组织进行灌流。在灌流过程中，将金黄仓鼠的垂体组织暴露于褪黑素中会导致LH基础分泌减少，但无论解剖时间如何，均不影响GnRH刺激的LH或FSH释放。然而，存在某种昼夜因素会降低夜间解剖的组织对GnRH刺激的FSH反应性。提示褪黑素可能是造成这种昼夜差异的原因。因此，褪黑素可直接作用于垂体前叶以降低基础LH分泌，并且褪黑素或其他一些昼夜因素可在体内发挥作用，降低夜间垂体对GnRH刺激的FSH分泌。
