Weiss J, Harris P E, Halvorson L M, Crowley W F, Jameson J L
Department of Medicine, Massachusetts General Hospital, Boston 02114.
Endocrinology. 1992 Sep;131(3):1403-8. doi: 10.1210/endo.131.3.1505470.
Maintenance of FSH biosynthesis requires ongoing exposure to pulsatile GnRH. Recent data demonstrate that activin also stimulates FSH biosynthesis. We used a perifused pituitary system to examine regulation of FSH beta mRNA levels by pulsatile GnRH and activin. Hourly pulses of 10 nM GnRH increased FSH beta mRNA levels by 3-fold. In the same experiment, continuous infusion of 50 ng/ml activin elicited a 50-fold increase in FSH beta mRNA. This magnitude of response to activin in perifusion was unexpected, as only a 2.7-fold increase in FSH beta mRNA was observed when activin was administered to pituitary cells that were cultured in dishes. Since perifusion columns, unlike culture dishes, are exposed to a continuous supply of fresh medium, we examined the possibility that endogenous factors produced by pituitary cells cultured in dishes were stimulating the cells in a paracrine fashion, thereby precluding the full response to exogenously added activin. The kinetics of FSH beta mRNA expression were examined immediately after pituitary dispersion and at different times after culturing the cells in plates. FSH beta mRNA levels fell rapidly after dispersion to 8% of initial levels and remained low over 8 h. Thereafter, FSH beta mRNA levels increased slowly and exceeded initial levels by the second day of culture. In a parallel set of experiments, when medium conditioned by exposure to plated cells was applied to the perifusion system, FSH beta mRNA levels were selectively stimulated (6-fold). These data suggest the removal during dispersion and subsequent accumulation in culture of pituitary-derived factors that are important for the maintenance of FSH beta mRNA levels. We conclude that activin plays a greater role in the regulation of FSH beta mRNA levels than was suggested by previous experiments employing static culture systems in which autocrine or paracrine stimulation may have obscured the effects of exogenously added activin.
促卵泡激素（FSH）生物合成的维持需要持续暴露于脉冲式促性腺激素释放激素（GnRH）。近期数据表明，激活素也能刺激FSH生物合成。我们使用了一种灌流垂体系统来研究脉冲式GnRH和激活素对FSHβ mRNA水平的调控。每小时给予10 nM GnRH脉冲可使FSHβ mRNA水平增加3倍。在同一实验中，持续输注50 ng/ml激活素可使FSHβ mRNA增加50倍。在灌流实验中激活素引起的这种反应幅度出乎意料，因为当将激活素添加到培养皿中培养的垂体细胞时，仅观察到FSHβ mRNA增加2.7倍。由于与培养皿不同，灌流柱可接触到持续供应的新鲜培养基，我们推测培养皿中培养的垂体细胞产生的内源性因子可能以旁分泌方式刺激细胞，从而阻碍了对外源性添加激活素的完全反应。在垂体分散后以及在平板中培养细胞后的不同时间，立即检测FSHβ mRNA表达的动力学。分散后FSHβ mRNA水平迅速下降至初始水平的8%，并在8小时内保持较低水平。此后，FSHβ mRNA水平缓慢上升，在培养的第二天超过初始水平。在一组平行实验中，当将接触平板细胞后的条件培养基应用于灌流系统时，FSHβ mRNA水平被选择性刺激（增加6倍）。这些数据表明，在分散过程中去除了对维持FSHβ mRNA水平很重要的垂体源性因子，随后在培养过程中这些因子积累。我们得出结论，与先前使用静态培养系统的实验相比，激活素在FSHβ mRNA水平调控中发挥的作用更大，在静态培养系统中，自分泌或旁分泌刺激可能掩盖了外源性添加激活素的作用。
