Nitroxyl increases force development in rat cardiac muscle
Nitroxyl increases force development in rat cardiac muscle
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DOI：
10.1113/jphysiol.2007.129254
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发表时间：
2007-05-01
影响因子：
5.5
通讯作者：
Gao, Wei Dong
中科院分区：
文献类型：
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作者：
Dai, Tieying;Tian, Ye;Gao, Wei Dong
氮氧基(HNO)供体是一氧化氮(NO)的还原异构体，在体内和体外发挥正性心脏变力/肌力作用，部分原因是它们促进了钙离子循环进入和流出肌浆网。在这里，我们测试了HNO的心脏作用是否进一步涉及肌丝-钙相互作用的变化。将完整的大鼠右室小梁固定在力传感器和运动臂之间，用Krebs-Henseleit(K-H)溶液(pH 7.4，室温)灌流，用Fura-2离子电泳法测定[Ca~(2+)]_i，肌节长度设置为2.2~2.3微米，用Angeli‘s盐(As；Na_2N_2O_3)供体的HNO可剂量依赖性地增加扭体力和[Ca~(2+)]i瞬变(从50~1000mU/M)。力量的增加超过了瞬间的[Ca~(2+)]，尤其是在较高剂量时(332+/-33%比221+/-27%，P<；0.01)。As/HNO(250µM)在任何给定的[Ca~(2+)](O)(0.5-2.0 mm)下，在不改变Ca~(2+)瞬变的情况下，增加了发展力。在稳态激活过程中，As/HNO(250mM)增加了最大钙激活力(F-max，106.8+/-4.3vs86.7+/-4.2mN mm(-2)，n=7-8，P<；0.01)，但不影响50%激活所需的钙(Ca-50，0.44+/-0.04mU，不显著)或希尔系数(4.75+/-0.67vs5.02+/-1.1，不显著)。AS/HNO不改变肌原纤维MG-ATPase活性，支持对肌丝本身的影响。硫醇还原剂二硫苏糖醇(DTT，5.0 mM)既可阻止也可逆转HNO作用，证实了AS/HNO氧化还原的敏感性。最后，NO(来自DEA/NO)不能模拟AS/HNO的心脏效应。因此，除了报道的钙循环的变化外，HNO还起到了心脏钙增敏剂的作用，在不改变肌动蛋白ATPase活性的情况下增加了最大力量。这很可能是由于含有HNO靶标的活性硫基的肌丝蛋白的调节。
Donors of nitroxyl (HNO), the reduced congener of nitric oxide (NO), exert positive cardiac inotropy/lusitropy in vivo and in vitro, due in part to their enhancement of Ca2+ cycling into and out of the sarcoplasmic reticulum. Here we tested whether the cardiac action of HNO further involves changes in myofilament-calcium interaction. Intact rat trabeculae from the right ventricle were mounted between a force transducer and a motor arm, superfused with Krebs-Henseleit (K-H) solution (pH 7.4, room temperature) and loaded iontophoretically with fura-2 to determine [Ca2+]i. Sarcomere length was set at 2.2-2.3 mu m. HNO donated by Angeli's salt (AS; Na2N2O3) dose-dependently increased both twitch force and [Ca2+]i transients (from 50 to 1000 mu M). Force increased more than [Ca2+], transients, especially at higher doses (332 +/- 33% versus 221 +/- 27%, P < 0.01 at 1000 mu M). AS/HNO (250 mu M) increased developed force without changing Ca2+ transients at any given [Ca2+](o) (0.5-2.0 mM). During steady-state activation, AS/HNO (250 mu M) increased maximal Ca2+- activated force (F-max, 106.8 +/- 4.3 versus 86.7 +/- 4.2 mN mm(-2), n = 7-8, P < 0.01) without affecting Ca2+ required for 50% activation (Ca-50, 0.44 +/- 0.04 versus 0.52 +/- 0.04 mu M, not significant) or the Hill coefficient (4.75 +/- 0.67 versus 5.02 +/- 1.1, not significant). AS/HNO did not alter myofibrillar Mg-ATPase activity, supporting an effect on the myofilaments themselves. The thiol reducing agent dithiothreitol (DTT, 5.0 mm) both prevented and reversed HNO action, confirming AS/HNO redox sensitivity. Lastly, NO (from DEA/NO) did not mimic AS/HNO cardiac effects. Thus, in addition to reported changes in Ca2+ cycling, HNO also acts as a cardiac Ca2+ sensitizer, augmenting maximal force without altering actomyosin ATPase activity. This is likely to be due to modulation of myofilament proteins that harbour reactive thiolate groups that are targets of HNO.