Zakharov S I, Pieramici S, Kumar G K, Prabhakar N R, Harvey R D
Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio 44106-4970, USA.
Circ Res. 1996 May;78(5):925-35. doi: 10.1161/01.res.78.5.925.
It has recently been demonstrated that NO plays an obligatory role in muscarinic inhibition of beta-adrenergically stimulated ion channels in cardiac sinoatrial node cells (J Gen Physiol. 1995;106:45-65). We looked for evidence that NO might play a similar role in ventricular cells by using histochemical staining for NO synthase (NOS) activity and whole-cell patch-clamp recording of cAMP-regulated Cl- currents. Myocytes isolated from guinea pig hearts stained positively for NADPH-diaphorase activity, suggesting that these cells do express NOS. Acetylcholine (ACh) inhibition of the R(-)-isoproterenol bitartrate (Iso)-activated Cl- current was also reversed by the cGMP-lowering agents LY-83583 and methylene blue, consistent with idea that NO activation of guanylate cyclase may contribute to muscarinic responses. However, LY-83583 and methylene blue activated the Cl- current in the presence of subthreshold concentrations of Iso alone, suggesting that their effects may not be due to antagonism of an NO/cGMP-dependent response. Furthermore, ACh inhibition of Iso-activated Cl- currents could not be mimicked by the NO donors sodium nitroprusside,3-morpholinosydnonimine, and spermine-NO. Similarly, ACh inhibition of the Iso-activated Cl- current could not be blocked by the NOS inhibitor NG-monomethyl-L-arginine. These results indicate that even though ventricular myocytes possess NOS activity, NO production does not play an important role in muscarinic inhibition of beta-adrenergically regulated Cl- channels in these cells.
最近有研究表明，一氧化氮（NO）在心脏窦房结细胞中对毒蕈碱抑制β-肾上腺素能刺激的离子通道起着必不可少的作用（《普通生理学杂志》。1995年；106:45 - 65）。我们通过对一氧化氮合酶（NOS）活性进行组织化学染色以及对cAMP调节的氯离子电流进行全细胞膜片钳记录，来寻找NO在心室细胞中可能发挥类似作用的证据。从豚鼠心脏分离的心肌细胞对NADPH - 黄递酶活性染色呈阳性，表明这些细胞确实表达NOS。毒蕈碱样乙酰胆碱（ACh）对R(-)-异丙肾上腺素酒石酸盐（Iso）激活的氯离子电流的抑制作用，也被降低cGMP的药物LY - 83583和亚甲蓝所逆转，这与NO激活鸟苷酸环化酶可能参与毒蕈碱样反应的观点一致。然而，LY - 83583和亚甲蓝在仅存在阈下浓度的Iso时就能激活氯离子电流，这表明它们的作用可能并非由于拮抗NO/cGMP依赖性反应。此外，NO供体硝普钠、3 - 吗啉代辛二亚胺和精胺 - NO无法模拟ACh对Iso激活的氯离子电流的抑制作用。同样，NOS抑制剂NG - 单甲基 - L - 精氨酸也不能阻断ACh对Iso激活的氯离子电流的抑制作用。这些结果表明，尽管心室肌细胞具有NOS活性，但NO的产生在这些细胞中毒蕈碱抑制β - 肾上腺素能调节的氯离子通道过程中并不起重要作用。
