Luck M R, Jungclas B
Institute for Hormone and Fertility Research, Hamburg, Federal Republic of Germany.
J Endocrinol. 1988 Feb;116(2):247-58. doi: 10.1677/joe.0.1160247.
Bovine granulosa cells secrete oxytocin when cultured in a serum-supplemented medium. The time-course of secretion is similar to that in the early corpus luteum in vivo, with a delay of 1 to 2 days followed by a peak and decline over the first 5 days of culture. We have investigated the basis of this time-course in vitro and studied the temporal characteristics of the stimulatory actions of ascorbic acid and adrenaline on this process. Cells cultured on stirred microcarriers showed a similar pattern of secretion of oxytocin to those cultured on conventional flat plates, despite continuing and rapid mitosis. This indicated that the secretion profile in conventional culture was not an artifact related to the cessation of mitosis. Furthermore, secretion of oxytocin and progesterone by cells on microcarriers was stimulated without a corresponding change in mitotic rate, showing that the secretion per cell had been increased. In conventional culture, addition of ascorbic acid to culture media (0.5 mmol/l) increased the secretion of oxytocin (up to 4.5-fold) but only if ascorbic acid was present during the first day of culture. The cells showed a progressive refractoriness to stimulation after 12 h. Since the time-course of secretion was unaltered by treatment, this resulted in a delay of 1 to 2 days before the action of the ascorbate was seen. The secretion of progesterone was similarly affected but with less stimulation and less consistency. In contrast, cells treated with adrenaline (10 mumol/l) secreted more oxytocin on the day of treatment and did so at any time during culture provided that there was sufficient basal secretion of hormone. Adrenaline also failed to alter the time-course of secretion but treated cells showed a persistent response, maintaining enhanced secretion for up to 3 days after the adrenaline had been removed. Ascorbate and adrenaline were highly synergistic in their effects, provided that the ascorbate was present from the start of culture; the response to adrenaline strongly reflected the degree of ascorbate stimulation. We conclude that granulosa cells secrete oxytocin according to an inherent time-schedule and that there is a limited period during which they can respond to ascorbate. Since ascorbate is required for the biosynthesis of oxytocin, this suggests that the availability of ascorbate during corpus luteum formation may determine the amount of oxytocin which can be released subsequently in response to catecholamines.
牛颗粒细胞在补充血清的培养基中培养时会分泌催产素。分泌的时间进程与体内早期黄体中的相似，有1至2天的延迟，随后在培养的前5天出现一个峰值并下降。我们研究了体外这种时间进程的基础，并研究了抗坏血酸和肾上腺素对这一过程刺激作用的时间特征。在搅拌的微载体上培养的细胞，尽管有持续且快速的有丝分裂，但催产素的分泌模式与在传统平板上培养的细胞相似。这表明传统培养中的分泌模式不是与有丝分裂停止相关的假象。此外，微载体上的细胞分泌催产素和孕酮受到刺激，而有丝分裂率没有相应变化，这表明每个细胞的分泌增加了。在传统培养中，向培养基中添加抗坏血酸（0.5 mmol/L）可增加催产素的分泌（高达4.5倍），但前提是抗坏血酸在培养的第一天就存在。12小时后，细胞对刺激表现出逐渐的不应性。由于分泌的时间进程不受处理影响，这导致抗坏血酸作用出现前有1至2天的延迟。孕酮的分泌也受到类似影响，但刺激较少且一致性较差。相比之下，用肾上腺素（10 μmol/L）处理的细胞在处理当天分泌更多的催产素，并且只要激素有足够的基础分泌，在培养的任何时候都如此。肾上腺素也未能改变分泌的时间进程，但处理过的细胞表现出持续反应，在去除肾上腺素后长达3天维持增强的分泌。如果从培养开始就存在抗坏血酸，抗坏血酸和肾上腺素在其作用上具有高度协同性；对肾上腺素的反应强烈反映了抗坏血酸刺激的程度。我们得出结论，颗粒细胞根据内在的时间表分泌催产素，并且它们对抗坏血酸作出反应的时期有限。由于催产素的生物合成需要抗坏血酸，这表明黄体形成过程中抗坏血酸的可用性可能决定随后响应儿茶酚胺而释放的催产素的量。
