摘要
本工作探讨VIP在下丘脑水平对PRL和β-EP释放的调节,结果表明,所用三种剂量的VIP均显著兴奋PRL的释放,兴奋效应与VIP剂量相关;各剂量VIP对β-EP的释放均无明显影响,提示VIP可经某种下丘脑机制兴奋PRL的释放。我们的结果还进一步证明,VIP兴奋PRL的释放似与抑制DA的作用无关。另外,应用体外培养的正常大鼠前叶垂体细胞,观察10^(-10)～10^(-6)mol/L的VIP对PRL和β-EP释放的影响及其与细胞外Ca^(2+)浓度的关系,看到VIP可直接兴奋垂体细胞释放PRL,且具剂量相关效应;VIP兴奋PRL的释放与胞外Ca^(2+)浓度无关。剂量达10^(-7)mol/L的VIP仍不影响垂体细胞β-EP的释放。另用新鲜制备的正常大鼠离散前叶垂体细胞,比较VIP对细胞内cAMP和胞内Ca^(2+)的影响,结果表明,10^(-7)mol/L的VIP显著升高细胞内Ca^(2+)浓度,也显著升高胞内cAMP的水平,但后者可被2.0mmol/L EGTA消除,说明胞内cAMP水平的改变有赖于胞外Ca^(2+)的存在,联想上述VIP兴奋PRL的释放却与胞外Ca^(2+)的存在与否无关,提示VIP兴奋PRL的释放似由胞内Ca^(2+)而非cAMP介导信息跨膜传递。
Vasoactive intestinal polypeptide (VIP) when injected in doses of 0.2, 1.0 and 5.0μg into the third cerebral ventricle( 3 rd. V. I) of conscious, unrestra-ned male rats, outfitted with chronic 3 rd. V.I and jugular cannulae,markedly increased plasma prolactin (PRL) levels, and were dose-dependent response. All tested doses of VIP did not modify plasma β-endorphin (β-EP) levels. Spiroperidol (Spi, 0.5mg/kg, i. v) , a very potent dopamine receptor blocker, also significantly increased plasma PRL levels. The injection of Spi (0.5mg/kg, i. v) followed by injection of VIP (1.0ug, 3rd. V. 1) markedly increased plasma PRL levels, compared with Spi (0.5 mg/kg, i. v) alone or VIP (1.0μg,3 rd. V. I) alone. When VIP (10-8~10-8mol/L) were added to the medium of anterior pituitary cell culture, also caused dose-dependent increase of PRL secretion. The depletion of extracellular Ca2+ by EGTA (2.0 mmol/L) did not change the VIP stimulated PRL secretion, but inhibited the VIP (10-7mol/L) stimulated cAMP accumulation. Also, VIP (10~7mol/L) significantly elevated intracellular Ca2+ concentration. These results indicate that VIP stimulates PRL release via hypothalamic mechanism, but not via the inhibition of dopamine in vivo,and that it might be the calcium but not cAMP mediated the intracellular signalling in the VIP stimulated PRL release in vitro.
出处
《基础医学与临床》
CSCD
1992年第6期33-40,共8页
Basic and Clinical Medicine
基金
国家自然科学基金 (编号38970313)
关键词
催乳素
内啡呔
环磷酸腺苷
prolactin β-endorphin spiroperidol EGTA cAMP Ca^(2+)
