Interaction and Cytotoxic Effect of Superoxide and NO in Reperfusion Injury

通过同时测量细胞内Ca^<2+> ([Ca^<2+>]i)和收缩功能来检测过氧亚硝酸盐（ONOO^-）对培养心肌细胞的影响。暴露于0.2mM ONOO^-时，[Ca^<2+>]i在5分钟内增加到超过收缩期水平，同时自发收缩减少，随后完全停止。添加l型Ca^<2+>通道阻滞剂或去除细胞外Ca^<2+>可阻止ONOO^-诱导的[Ca^<2+>]i的增加；表明[Ca^<2+>]i的增加是由Ca^<2+>通过质膜流入增强引起的，而不是由肌浆网（SR）释放增强引起的。ONOO^-处理后，细胞内的质膜流动性和硫代巴比妥酸反应物质（TBARS）浓度保持不变。即使在额外的皂苷（5muM）处理诱导的[Ca^<2+>]i大量增加的情况下，肌细胞的完全停止收缩仍然存在。综上所述，ONOO^-通过干扰质膜中的Ca^<2+>运输系统，增加肌细胞中的[Ca^<2+>]i，并损害收缩蛋白。

The effects of peroxynitrite (ONOO^-) on cultured cardiac myocytes were examined by simultaneous measurements of intracellular Ca^<2+> ([Ca^<2+>]i) and contractile function. On exposure to 0.2mM ONOO^-, [Ca^<2+>]i increased to beyond the systolic level within 5 min with a concomitant decrease in spontaneous contraction, followed by complete arrest. Addition of a L-type Ca^<2+> channel blocker or removal of extracellular Ca^<2+> prevented the ONOO^--induced increase in [Ca^<2+>]i ; indicating that the increase in [Ca^<2+>]i was caused by the enhanced influx of Ca^<2+> through the plasma membrane and not by the enhanced release from sarcoplasmic reticulum (SR). Plasma membrane fluidity and concentration of the thiobarbiturate acid-reactive substance (TBARS) in the cells remained unchanged by the ONOO^- treatment. The complete cessation of contraction of myocytes persisted even under the massive increase in [Ca^<2+>]i which was induced by an additional saponin (5muM) treatment. In conclusion, ONOO^- increases [Ca^<2+>]i in myocytes through disturbance of Ca^<2+> transport systems in the plasma membrane and impairs contractile protein.