Molecular mechanism of gonadotropin and prolactin release from pituitary cells

LH- rh诱导垂体前叶LH，泌乳素由TRH分泌。溴隐亭是一种多巴胺激动剂，可用于治疗催乳素瘤。这种药不仅能抑制催乳素的释放，还能缩小肿瘤的大小。本研究旨在阐明催乳素和LH分泌的受体后机制，以及多巴胺抑制催乳素释放的分子机制。（方法）采用大鼠垂体前叶细胞和HG_3细胞系进行实验。（结果）(1)Maitotoxin诱导Ca^<2+>内流至细胞内并释放催乳素。(2) TRH刺激-^<32>P在磷脂酰肌醇转化中的掺入。(3)磷脂酶C，经钙活化，将磷脂酰肌醇溶解为二酰基甘油和三磷酸接种糖醇，诱导泌乳素释放。(4)垂体细胞蛋白激酶C被PMA激活。PMA刺激LH和催乳素分泌。TRH诱导GH_3细胞泌乳素激酶C易位。(5) TRH刺激经^ 3h -花生四烯酸预孵育的垂体细胞的磷脂释放花生四烯酸。(6)垂体细胞与花生四烯酸酯孵育后释放催乳素和LH。(7)环氧合酶产物对催乳素释放无影响，而5-HETE和白三烯、5-脂氧合酶产物可诱导催乳素和LH分泌。(8)多巴胺抑制PMA、花生四烯酸酯、磷脂酶C、乳酸菌毒素和5-HETE刺激的催乳素释放。在没有多巴胺受体的GH_3细胞中，TRH诱导的催乳素释放不受多巴胺的抑制。（结论）TRH和LH- rh分别通过二酰基甘油、蛋白激酶和钙、花生四烯酸体系刺激催乳素和LH。多巴胺会抑制这些信号。

LH-RH induces LH from anterior pituitary gland and prolactin is secreted by TRH. Bromocriptine, a dopamine agonist, is useful for the treatment of prolactinoma. This drug not only suppresses prolactin release but also reduces tumor size. The purpose of this research is to clarify the postreceptor mechanism in prolactin and LH secretion, and molecular mechanism of inhibition of prolactin release by dopamine. (METHODS) Rat anterior pituitary cells and HG_3 cell line were used for the experiment. (RESULTS) (1) Maitotoxin induced Ca^<2+> influx into the cells and prolactin release.(2) TRH stimulated-^<32>P incorporation in phosphatidyl inositol turnover. (3)Phospholipase C, Activated by calcium, dissolved phosphatidyl inositol into diacylglycerol and inocitol triphosphate, and induced prolactin release. (4) Protein kinase C in pituitary cells was activated PMA. PMA stimulated LH and prolactin secretion. TRH induced the translocation of prolactin kinase C In GH_3 cells. (5) TRH stimulated arachidonate release from the phospholipids of pituitary cells preincubated with ^3H-arachidonate. (6) Prolactin and LH was released when pituitary cells was incubated with arachidonate. (7) Products of cyclooxygenase has no effects on prolactin release, although 5-HETE and leukotriene, 5-lipoxygenase products, induced prolactin and LH secretion.(8) Dopamine inhibited prolactin release stimulated by PMA, arachidonate, phospholipase C, maitotoxin and 5-HETE. TRH- induced prolactin release was not inhibited by dopamine in GH_3 cells which has no dopamine receptor. (CONCLUSION) TRH and LH-RH stimulated prolactin and LH respectively though diacylglycerol, protein kinase and calcium, arachidonate system. Dopamine inhibit every these signals.