Twort C H, van Breemen C
Department of Pharmacology, University of Miami School of Medicine, Florida.
Circ Res. 1988 May;62(5):961-4. doi: 10.1161/01.res.62.5.961.
The purpose of this study was to investigate the effects of the intracellular messenger cyclic GMP (cGMP) on sequestration of cytosolic calcium (Ca2+) into the intracellular Ca2+ store (the sarcoplasmic reticulum) of vascular smooth muscle. Using saponin-skinned primary cultures of rat aortic smooth muscle, we investigated the effect of cGMP on 45Ca uptake in monolayers of cells. The intracellular store was loaded with Ca2+ by exposing the skinned cells to a 45Ca-labeled 1-microM free Ca2+-containing solution for varying durations (0-20 minutes). Addition of 10 microM cGMP to six monolayers increased both the initial Ca2+ uptake at 2 minutes (control, 240 +/- 8 pmol Ca2+/10(6) cells; + cGMP 295 +/- 7; mean +/- SEM; n = 6, p less than 0.01) and the final steady-state uptake reached at 20 minutes (control, 0.96 +/- 0.03 nmol Ca2+/10(6) cells; + cGMP 1.12 +/- 0.03, p less than 0.02). This stimulation of uptake was quantitatively similar to that caused by 10 microM cyclic AMP. It occurred at varying ambient cytosolic Ca2+ concentrations (0.1-1.0 microM Ca2+) and was not further enhanced by addition of 10 microM cGMP-dependent protein kinase. The dose-response of stimulation of Ca2+ uptake with cGMP indicated an ED50 of 5 nM cGMP. The release of Ca2+ from the sarcoplasmic reticulum in response to inositol 1,4,5-trisphosphate or caffeine was unaffected by cGMP. We conclude that the relaxation of vascular smooth muscle with cGMP-producing vasodilators is mediated in part by sequestration of cytosolic Ca2+ by the sarcoplasmic reticulum.
本研究的目的是探讨细胞内信使环鸟苷酸（cGMP）对血管平滑肌细胞溶质钙（Ca2+）隔离至细胞内Ca2+储存库（肌浆网）的影响。利用皂素处理的大鼠主动脉平滑肌原代培养物，我们研究了cGMP对单层细胞45Ca摄取的影响。通过将去垢剂处理的细胞暴露于含45Ca标记的1微摩尔游离Ca2+溶液中不同时间（0 - 20分钟），使细胞内储存库加载Ca2+。向六个单层细胞中添加10微摩尔cGMP，增加了2分钟时的初始Ca2+摄取量（对照组，240±8皮摩尔Ca2+/10^6个细胞；+ cGMP组为295±7；平均值±标准误；n = 6，p < 0.01）以及20分钟时达到的最终稳态摄取量（对照组，0.96±0.03纳摩尔Ca2+/10^6个细胞；+ cGMP组为1.12±0.03，p < 0.02）。这种摄取刺激在数量上与10微摩尔环磷酸腺苷引起的相似。它在不同的细胞溶质Ca2+环境浓度（0.1 - 1.0微摩尔Ca2+）下发生，并且添加10微摩尔cGMP依赖性蛋白激酶后未进一步增强。cGMP刺激Ca2+摄取的剂量反应表明其半数有效剂量（ED50）为5纳摩尔cGMP。肌浆网对肌醇1,4,5 - 三磷酸或咖啡因的Ca2+释放不受cGMP影响。我们得出结论，产生cGMP的血管舒张剂使血管平滑肌舒张部分是通过肌浆网隔离细胞溶质Ca2+来介导的。
