Transmembrane signal transduction in vascular smooth muscle and endothelial cells and physilogic responese

单胺类如去甲肾上腺素、血清素和组胺是有效的血管收缩剂。本研究的目的是研究受体介导的膜肌醇磷脂的水解及其调节，这导致在血管平滑肌中产生两种细胞内第二信使，肌醇1，4，5-三磷酸（IP 3）和甘油二酯。采用<32>~ 3 H-肌醇标记法和~ 3 H-肌醇标记法分别对兔离体主动脉平滑肌细胞和完整主动脉环进行标记。这些胺通过激活<alpha>^2-肾上腺素能、5-HT 2和H1受体，剂量依赖性地刺激磷酸肌醇的分解。各激动剂的磷脂酰肌醇标记曲线和收缩曲线相似。我们发现，鸟嘌呤核苷酸抑制（Gi）蛋白偶联5 HT受体的磷脂酶C和佛波醇酯，如TPA调节5 HT刺激的肌醇磷脂的水解。每种激动剂的特定调节机制可能存在于受体活化和磷酸肌醇分解之间，因为响应于每种激动剂的磷酸肌醇（PI、PIP和PIP 2）的早期降解和再合成是不同的。磷酸肌醇标记和这些胺诱导的收缩与细胞外Ca^++内流的内流不同地偶联。受体介导的磷酸肌醇的分解受环核苷酸（环AMP和环GMP）的调节。佛波酯（如TPA）可诱导离体兔主动脉的持续收缩，这种收缩完全依赖于细胞内Ca^++。TPA抑制乙酰胆碱诱导的内皮依赖性舒张，但不抑制硝酸甘油诱导的内皮依赖性舒张。

Monoamines such as norepinephrine, serotonin, and histamine are potent vasoconstrictors. The goal of this study was to examine receptor-mediated hydrolysis of membrane inositol phospholipids and its regulation, which results in the generation of two intracellular second messengers, inositol 1,4,5-trisphosphate(IP3) and diacylglycerol in vascular smooth muscles. We adopted ^<32>Pi labeling method in intact aortic ring preparatin and ^3H-inositol labeling method in cultured aortic smooth muscle cells obtained from rabbits. These amines stimulated phosphoinositides breakdown dose-dependently through <alpha>^2-adrenergic, 5HT2 and H1 receptor activations. Phosphatidylinositol labeling curve and contractin curve for each agonist were similar. We found that a guanine nucleotide inhibitory (Gi) protein coupled 5HT receptor to phospholipase C and phorbol esters such as TPA modulated 5HT-stimu-lated hydrolysis of inositol phospholipids. Specific regulatory mechanisms for each agonist may exist between receptor activatin and phosphoinositides breakdown, as early degradation and resynthesis of phosphoinositides (PI,PIP and PIP2) in response to each agonist were different. Phosphoinositides labeling and the contractin induced by these amines were differently coupled with the influx of extracellular Ca^<++> influx. Receptor-mediated phosphoinositides breakdown was regulated by cyclic nucleotides ( cyclic AMP and cyclic GMP ). Phorbol esters such as TPA induced a sustained contraction of isolated rabbit aorta that was entirely dependent on intracellular Ca^<++>. TPA inhibited the endothelium dependent relaxation induced by acetylcholine, but not the nitroglycerin-induced relaxation.