Kanai A J, Mesaros S, Finkel M S, Oddis C V, Birder L A, Malinski T
Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708, USA.
Am J Physiol. 1997 Oct;273(4):C1371-7. doi: 10.1152/ajpcell.1997.273.4.C1371.
Nitric oxide (NO) has been implicated in endogenous control of myocardial contractility. However, NO release has not yet been demonstrated in cardiac myocytes. Accordingly, endogenous NO production was measured with a porphyrinic microsensor positioned on the surface of individual neonatal or adult rat ventricular myocytes (n > 6 neonatal and adult cells per experiment). In beating neonatal myocytes, there was no detectable spontaneous NO release with each contraction. However, norepinephrine (NE; 0.25-1 microM) elicited transient NO release from beating neonatal (149 +/- 11 to 767 +/- 83 nM NO) and noncontracting adult (157 +/- 13 to 791 +/- 89 nM NO) cells. NO was released by adrenergic agonists with the following rank order of potency: isoproterenol (beta1beta2) > NE (alpha/beta1) > dobutamine (beta1) approximately epinephrine (alpha/beta1beta2) > tertbutylene (beta2); NO was not released by phenylephrine (alpha). NE-evoked NO release was reversibly blocked by N(G)-monomethyl-L-arginine, trifluoperazine, guanosine 5'-O-(2-thiodiphosphate), and nifedipine but was enhanced by 3-isobutyl-1-methylxanthine (0.5 mM = 14.5 +/- 1.6%) and BAY K 8644 (10 microM = 11.9 +/- 1%). NO was also released by A-23187 (10 microM = 884 +/- 88 nM NO), guanosine 5'-O-(3-thiotriphosphate) (1 microM = 334 +/- 56 nM NO), and dibutyryl adenosine 3',5'-cyclic monophosphate (10-100 microM = 35 +/- 9 to 284 +/- 49 nM NO) but not by ATP, bradykinin, carbachol, 8-bromoguanosine 3',5'-cyclic monophosphate, or shear stress. This first functional demonstration of a constitutive NO synthase in cardiac myocytes suggests its regulation by a beta-adrenergic signaling pathway and may provide a novel mechanism for the coronary artery vasodilatation and enhanced diastolic relaxation observed with adrenergic stimulation.
一氧化氮（NO）与心肌收缩力的内源性调控有关。然而，心肌细胞中尚未证实有NO释放。因此，我们使用卟啉微传感器测量单个新生或成年大鼠心室肌细胞表面的内源性NO生成（每个实验中新生和成年细胞均>6个）。在跳动的新生心肌细胞中，每次收缩时均未检测到自发的NO释放。然而，去甲肾上腺素（NE；0.25 - 1 microM）可引起跳动的新生细胞（149±11至767±83 nM NO）和不收缩的成年细胞（157±13至791±89 nM NO）短暂释放NO。肾上腺素能激动剂释放NO的效力顺序如下：异丙肾上腺素（β1β2）>NE（α/β1）>多巴酚丁胺（β1）≈肾上腺素（α/β1β2）>叔丁喘宁（β2）；苯肾上腺素（α）不释放NO。NE诱发的NO释放可被N（G）-单甲基-L-精氨酸、三氟拉嗪、鸟苷5'-O-（2-硫代二磷酸）和硝苯地平可逆性阻断，但可被3-异丁基-1-甲基黄嘌呤（0.5 mM = 14.5±1.6%）和BAY K 8644（10 microM = 11.9±1%）增强。A-23187（10 microM = 884±88 nM NO）、鸟苷5'-O-（3-硫代三磷酸）（1 microM = 334±56 nM NO）和二丁酰腺苷3'，5'-环磷酸（10 - 100 microM = 35±9至284±49 nM NO）也可释放NO，但ATP、缓激肽、卡巴胆碱、8-溴鸟苷3'，5'-环磷酸或剪切力则不能。心肌细胞中组成型NO合酶的这一首次功能证明表明其受β-肾上腺素能信号通路调控，并可能为肾上腺素能刺激时观察到的冠状动脉血管舒张和舒张期松弛增强提供一种新机制。
