Control of vascular tone by endothelium-derived relaxing and hyperpolarizing factors

应用膜片钳技术研究了内皮源性舒张因子（EDRF）和超极化因子（EDHF）对猪冠状动脉平滑肌细胞和内皮细胞血管张力的调控作用。我们表征了平滑肌细胞中两种主要的K通道，即atp敏感K通道（KATP）和Ca^<2+>激活K通道（Kca），并研究了EDRF和EDHF的靶通道。这些通道也是各种血管活性物质的靶器官，许多血管活性物质通过这些通道发挥作用。在细胞贴附斑块中，EDRF，即一氧化氮（NO），通过生成cGMP激活平滑肌细胞的Kca通道。我们还发现NO也激活了KATP通道和超极化膜。在由内而外的补丁中，NO没有激活这些通道。我们还研究了EDHF对平滑肌细胞离子通道的影响，平滑肌细胞位于内皮完整的冠状动脉条带附近。在N^ g -单甲基l -精氨酸（LNMMA）和吲哚美辛前，乙酰胆碱激活了平滑肌的Kca通道，表明EDHF的靶点是Kca通道。特异的Kca通道阻滞剂四乙基铵和白蜡毒素抑制了该通道，但特异的KATP通道阻滞剂格列本脲没有显著改变通道活性。我们还发现了从猪冠状动脉和主动脉内皮生成一氧化氮的新途径。与以往研究不同的是，组胺没有增加内皮细胞的胞浆Ca^<2+>，但增加了内皮细胞的cAMP。组胺在H_1受体拮抗剂存在的情况下产生NO，而在H_2受体拮抗剂存在的情况下，NO的产生明显受到抑制，说明组胺诱导的NO的产生是通过H_2受体和cAMP的产生介导的。磷酸二酯酶抑制剂Amrinone和腺苷酸环化酶激活剂folskoline从猪内皮中产生NO。这些结果表明，一氧化氮的产生存在一条新的途径，即在不增加胞质Ca^<2+>的情况下，通过增加cAMP来产生一氧化氮。少

Control of vascular tone by endothelium-derived relaxing (EDRF) and hyperpolarizing factors (EDHF) was studied in cultured porcine coronary artery smooth muscle cells and endothelial cells using patch clamp techniques. We characterized two major K channels in smooth muscle cells, i.e.ATP sensitive K channel (KATP) and Ca^<2+>-activated K channels (Kca) and studied the target channels for EDRF and EDHF.These channels were targets organs of various vasoactive substances as well, and many vasoactive aubstances exert their actions through thses channels.In cell-attached patches, EDRF,which is known as nitric oxide (NO), activated Kca channel of smooth muscle cells via production of cGMP.We also found that NO also activated KATP channels and hyperpolarized membrane. In inside-out patches NO did not activated thses channels. We also studied the effect of EDHF on the ionic channles of smooth muslce cells, where is located close to the coronary artery strips with intact endothelium. In the pre … More sence of N^G-monomethyl L-arginine (LNMMA) and indomethacine, acetylcholine activated Kca channels of smooth muscle, suggesting that the target of EDHF was Kca channels. Tetraethylammonium and charybdotoxin, specific Kca channel blockers, suppressed this channels but glibenclamide, a specific KATP channel blocker, did not significantly altered the channel activity.We also found new pathway for production of NO from endothelium of porcine coronary artery and aorta. Different from previous studies, histamine did not increased cytosolic Ca^<2+> in endothelium but increased cAMP in endothelium. Histamine produced NO in the presence of histamine H_1 receptor antagonist, but NO production was significantly suppressed in the presence of H_2 receptor antagonist, suggesting that the histamine-induced NO production was mediated by H_2 receptor and through cAMP production. Amrinone, a phosphodiesterase inhibitor, and folskoline, an activator of adenylate cyclase, produced NO from porcine endothelium. These results indicated that there in a new pathway of NO production and that NO is produced by increasing cAMP without increase in cytosolic Ca^<2+>. Less