Liu T C, Pu H F, Jackson G L
Department of Medical Technology, National Yang-Ming Medical College, Taipei, Taiwan, Republic of China.
Neuroendocrinology. 1994 Jul;60(1):62-8. doi: 10.1159/000126720.
Receptor-mediated activation of phospholipase C (PLC) which releases diacylglycerol and inositol trisphosphate has been implicated in the action of gonadotropin-releasing hormone (GnRH) on gonadotrophs. Previously we demonstrated that the synthetic diacylglycerol, phorbol 12-myristate 13-acetate (PMA) and PLC mimic the stimulatory effects of GnRH on both luteinizing hormone (LH) glycosylation and release. In this study we further investigated how PMA or PLC interact with GnRH to control LH release versus glycosylation. Cultured pituitary cells were incubated in the presence of radiolabeled precursors and GnRH (0, 1, or 100 nM), with or without PMA (10 nM) or PLC (0.24 U/ml) for 4 h. LH translation and glycosylation were monitored by measuring incorporation of [14C]alanine and [3H]glucosamine, respectively, into total (cell and medium) immunoprecipitable LH. Immunoreactive LH (IRLH) was measured by radioimmunoassay. Both PMA and PLC increased (p < 0.01) basal IRLH release, and IRLH release stimulated by 1 nM GnRH. Neither PMA nor PLC exerted an additive effect on IRLH release stimulated by 100 nM GnRH. The interactions between PMA or PLC and GnRH on IRLH release were significant (p < 0.01). Both PMA and PLC elevated (p < 0.01) total [3H]glucosamine-LH, but had no additive effect with 1 nM GnRH; PLC depressed (p < 0.05) the stimulatory effect of 100 nM GnRH, whereas PMA had no effect. The interactions between PMA or PLC and GnRH on LH glycosylation were significant (p < 0.01). PMA, PLC or GnRH alone did not affect total [14C]alanine-LH. In the presence of 1 or 100 nM GnRH, PLC, but not PMA, decreased (p < 0.05) total [14C]alanine-LH.(ABSTRACT TRUNCATED AT 250 WORDS)
受体介导的磷脂酶C（PLC）激活可释放二酰甘油和肌醇三磷酸，这与促性腺激素释放激素（GnRH）对促性腺细胞的作用有关。此前我们证明，合成二酰甘油、佛波醇12-肉豆蔻酸酯13-乙酸酯（PMA）和PLC可模拟GnRH对促黄体生成素（LH）糖基化和释放的刺激作用。在本研究中，我们进一步研究了PMA或PLC如何与GnRH相互作用以控制LH释放与糖基化。将培养的垂体细胞在放射性标记前体和GnRH（0、1或100 nM）存在下孵育，添加或不添加PMA（10 nM）或PLC（0.24 U/ml）4小时。通过分别测量[14C]丙氨酸和[3H]葡糖胺掺入总（细胞和培养基）免疫沉淀LH中的量来监测LH翻译和糖基化。通过放射免疫测定法测量免疫反应性LH（IRLH）。PMA和PLC均增加（p<0.01）基础IRLH释放以及1 nM GnRH刺激的IRLH释放。PMA和PLC对100 nM GnRH刺激的IRLH释放均无相加作用。PMA或PLC与GnRH之间对IRLH释放的相互作用具有显著性（p<0.01）。PMA和PLC均提高（p<0.01）总[3H]葡糖胺-LH，但与1 nM GnRH无相加作用；PLC降低（p<0.05）100 nM GnRH的刺激作用，而PMA无影响。PMA或PLC与GnRH之间对LH糖基化的相互作用具有显著性（p<0.01）。单独的PMA、PLC或GnRH均不影响总[14C]丙氨酸-LH。在1或100 nM GnRH存在下，PLC而非PMA降低（p<0.05）总[14C]丙氨酸-LH。（摘要截断于250字）
