Balligand J L, Kelly R A, Marsden P A, Smith T W, Michel T
Cardiovascular and Renal Divisions, Brigham and Women's Hospital, Boston, MA.
Proc Natl Acad Sci U S A. 1993 Jan 1;90(1):347-51. doi: 10.1073/pnas.90.1.347.
Nitric oxide (NO) synthesized from L-arginine is a ubiquitous intracellular chemical messenger and is involved in signal transduction in diverse mammalian cells, including vascular endothelium and neuronal tissues. The role of the NO-signaling pathway in the direct modulation of cardiac function is less well characterized. In this report, the effects of inhibitors of NO synthase (NOS) were examined in isolated neonatal and adult rat ventricular myocytes exposed to either muscarinic or adrenergic agonists. Carbachol (10 microM) caused a 91% inhibition of the spontaneous beating rate of cultured neonatal rat cardiac myocytes. N omega-monomethyl-L-arginine, an L-arginine analog that inhibits NOS, and methylene blue, an inhibitor of NO, blocked the negative chronotropic effect of carbachol but had no effect on the basal beating rate of these cells. The inhibition by N omega-monomethyl-L-arginine of the negative chronotropic effect of carbachol was reversed by adding excess L-arginine. The negative chronotropic effect of carbachol was also mimicked by analogs of cGMP, a second messenger implicated in mediating the action of NO in other cell types. Production of NO could be detected directly in carbachol-stimulated neonatal myocytes by using a reporter cell bioassay. The regulation of adrenergic responsiveness by the NO signaling system was also documented in studies of adult cardiac myocyte contractility. The NOS inhibitor N omega-nitro-L-arginine significantly increased the inotropic effect of the beta-adrenergic agonist isoproterenol on electrically stimulated adult rat ventricular myocytes, whereas this inhibitor had no effect on basal contractility. Inhibition of NO production by N omega-monomethyl-L-arginine in these cells, as measured by reporter cell bioassay, was also reversible with excess L-arginine. Thus, the physiologic response of isolated neonatal and adult ventricular myocytes to both muscarinic cholinergic and beta-adrenergic stimulation is mediated, at least in part, by products of an endogenous NOS.
由L-精氨酸合成的一氧化氮（NO）是一种普遍存在的细胞内化学信使，参与多种哺乳动物细胞的信号转导，包括血管内皮细胞和神经组织。NO信号通路在直接调节心脏功能方面的作用尚不十分明确。在本报告中，研究了一氧化氮合酶（NOS）抑制剂对分离的新生大鼠和成年大鼠心室肌细胞的影响，这些细胞分别暴露于毒蕈碱或肾上腺素能激动剂。卡巴胆碱（10微摩尔）可使培养的新生大鼠心肌细胞的自发搏动率抑制91%。Nω-单甲基-L-精氨酸是一种抑制NOS的L-精氨酸类似物，亚甲蓝是一种NO抑制剂，它们可阻断卡巴胆碱的负性变时作用，但对这些细胞的基础搏动率无影响。添加过量的L-精氨酸可逆转Nω-单甲基-L-精氨酸对卡巴胆碱负性变时作用效应的抑制。cGMP的类似物也可模拟卡巴胆碱的负性变时作用，cGMP是另一种细胞类型中介导NO作用的第二信使。通过使用报告细胞生物测定法可直接检测到卡巴胆碱刺激的新生心肌细胞中NO的产生。在成年心肌细胞收缩性研究中也证明了NO信号系统对肾上腺素能反应性的调节作用。NOS抑制剂Nω-硝基-L-精氨酸可显著增强β-肾上腺素能激动剂异丙肾上腺素对电刺激的成年大鼠心室肌细胞的正性肌力作用，而该抑制剂对基础收缩性无影响。通过报告细胞生物测定法测定，Nω-单甲基-L-精氨酸对这些细胞中NO产生的抑制作用也可被过量的L-精氨酸逆转。因此，分离的新生和成年心室肌细胞对毒蕈碱胆碱能和β-肾上腺素能刺激的生理反应至少部分是由内源性NOS的产物介导的。
