Determination of the target cells of activins and the mechanisms of FSH secretion stimulated by activins

本研究的目的是阐明激活素在脑下垂体中的作用机制。激活素刺激卵泡刺激素的分泌，而对促黄体生成素的分泌没有影响。但激活素如何刺激FSH分泌的作用机制尚不清楚。本研究利用流式细胞仪和荧光显微镜系统对激活素的复杂作用机制进行了研究。激活素A、AB、B的靶细胞通过[Ca^&lt；2+&gt；]_i对每种下丘脑释放激素的反应来表征。其中50-70%的靶细胞为CHRH，40-7%的靶细胞为TRH反应细胞。用细胞分选机纯化的细胞与激光处理的细胞结果相似。此外，一些Tie激活素反应细胞对GHRH和TRH都有反应，因此我们试图确定PRL分泌细胞、TRH反应细胞和促性腺激素细胞之间的关系。斑点杂交结果显示，黄体生成素分泌细胞中黄体生成素和卵泡刺激素分泌细胞的比例分别为6.23%和5.91%，而黄体生成素和卵泡刺激素分泌细胞中分泌细胞的比例分别为18.4%和15.5%。促性腺激素释放激素(GnRH)和促性腺激素释放激素(TRH)使PRL分泌细胞[Ca^&lt；2+1&gt；]_i升高。这些结果表明，在激活素的刺激下，将自身转化为FSH分泌细胞的靶细胞属于GH或PRL分泌细胞亚群。由于这些细胞的数量较少，其转化过程尚不清楚。

The purpose of the study is to clarify the mechanisms of the action of activin in the pituitary gland. Activin stimulates FSH secretion without eny effect on LH secretion. But the mechaanisms of the action how activin stimulates FSH secretion specifically is unknown. This sutdy was performed to clarify the mechanisms of the complicated effect of activin using FACS and fluorescence microscope system. The results of the study may have a important roles in reproductive medicine.The target cells of the activin A,AB,B were characterized by their responses in [Ca^<2+>]_i to each Hyopothalamic releasing hormone. 50-70% of the target cells of them were proved to be CHRH,and 40-7-%, TRH-respondirig cells. The results using purified cells by cell sorter and laser treatment were similar. Moreover some of tie activin-responding cells have response to both GHRH and TRH.Then we tired to determine the relationship between PRL secreting cells, TRH-responding cells, and gonadotrophs. The results of dot bloting assey revealed the populations of the LH and FSH secreting cells in the PRL secreting cells were 6.23% and 5.91% respectively, while the populations of the PRL secreting cells in the LH and FSH secreting cell were 18.4% and 15.5% respectively. GnRH as well as TRH increased [Ca^<2+1>]_i in the PRL secreting cells as determined by RHPA.These data suggests theat the target cells which transform itself to FSH-secretinng cells stimulated by the activin are in a subpopulation of GH or PRL-secreting cells. The process of the transformation of these cells was not clarified becaouse of the small population of these cells.