Cell-cell communication in the ovarian tissue and its regulation by pituitary prolactin : in case of GnRH and annexin 5

在卵巢组织中，黄体中的膜联蛋白5（钙-磷脂结合蛋白和GnRH的新靶点）的表达受到催乳素的抑制。在每日两次泌乳素激增的大鼠假妊娠期间，多巴胺激动剂2α-甲磺酸溴包络隐碱（CB-154）抑制泌乳素分泌，导致同一黄体细胞膜联蛋白5表达增加，出现TUNEL阳性反应。GnRH拮抗剂Cetrorelix局部应用于CB-154假孕大鼠的单侧卵巢囊，通过渗透泵完全抑制细胞凋亡和膜联蛋白5的表达，同时在对侧未处理的卵巢黄体细胞中观察到它们的表达。用渗透泵将GnRH激动剂（GnRHa）注入假妊娠大鼠的半侧卵巢囊，观察GnRH对黄体细胞的直接作用。GnRHa诱导相同黄体细胞凋亡和膜联蛋白5表达。由于黄体酮没有抑制CB-154处理的假妊娠大鼠的细胞凋亡和膜联蛋白5的表达，催乳素被认为直接抑制卵巢中的GnRH作用。综上所述，催乳素至少在一定程度上通过抑制局部GnRH的作用来维持黄体期的功能。（这项研究发表在内分泌学2003年144:3625-3631）。

In the ovarian tissue, the expression of annexin 5, a calcium-phospholipid binding protein and a novel target of GnRH, in the corpus luteum is suppressed by prolactin. During pseudopregnancy of rats in which two daily prolactin surges occur, inhibition of prolactin secretion by dopamine agonist, 2α-bromoergocriptine mesylate (CB-154), resulted in the augmentation of annexin 5 expression and the occurrence of TUNEL positive reaction in the same luteal cells. Local administration of GnRH antagonist, Cetrorelix, to unilateral ovarian bursa of a CB-154 administered pseudopregnant rat with an osmotic pump completely suppressed both apoptosis and annexin 5 expression, while they were observed in the luteal cells of the contralateral non-treated ovary. The direct effect of GnRH on luteal cells was examined by administering GnRH agonist (GnRHa) with an osmotic pump to hemilateral ovarian bursa of a pseudopregnant rat. GnRHa induced apoptosis and annexin 5 expression in the same luteal cells. Since the administration of progesterone did not suppressed apoptosis and annexin 5 expression in the CB-154 treated pseudopregnant rats, prolactin is thought to inhibit GnRH action directly in the ovary. Getting together, it is suggested that prolactin maintains the functional luteal phase at least partly by suppressing local GnRH action. (this work was published in Endocrinology 2003 144:3625-3631).