Kopustinskiene Dalia M, Liobikas Julius, Skemiene Kristina, Malinauskas Faustas, Toleikis Adolfas
Laboratory of Biochemistry, Institute for Biomedical Research of Kaunas University of Medicine, 50009, Kaunas, Lithuania.
Cell Physiol Biochem. 2010;25(2-3):181-6. doi: 10.1159/000276552. Epub 2010 Jan 12.
K(ATP) channel openers protect ischemic-reperfused myocardium by mimicking ischemic preconditioning, however, the protection mechanisms have not been fully clarified yet. Since the skinned fibers technique gives an opportunity to investigate an entire population of mitochondria in their native milieu, in this study we have investigated the effects of K(ATP) channel openers pinacidil and diazoxide on the respiration rate of rat heart mitochondria in situ, oxidizing physiological substrates pyruvate and malate (6+6 mM). Respiration rates were recorded by the means of Clark-type oxygen electrode in the physiological salt solution (37 degrees C). Our results showed that both pinacidil and diazoxide (60-1250 muM) in a concentration-dependent manner increased pyruvate-malate supported State 2 respiration rate of skinned cardiac fibers (59.1 +/- 5.1 nmol O/min/mg fiber dry weight, RCI 2.6 +/- 0.2, n=4) by 15-120%. Moreover, diazoxide did not affect, whereas pinacidil (60-1250 muM) decreased the State 3 respiration rate of skinned cardiac fibers (116.6 +/- 13.6 nmol O/min/mg fiber dry weight, RCI 2.3 +/- 0.2, n=4) by 4-27%. Thus, common effect for both K(ATP) channel openers is uncoupling of pyruvate and malate oxidizing mitochondria in skinned cardiac fibers, whereas pinacidil under same conditions also inhibits mitochondrial respiratory chain. Since mitochondria in situ resemble to the great extent mitochondria in vivo, our results suggest that uncoupling and/or respiratory chain inhibition could play a role in the cardioprotection by K(ATP) channel openers.
K(ATP)通道开放剂通过模拟缺血预处理来保护缺血再灌注心肌，然而，其保护机制尚未完全阐明。由于透皮纤维技术为在天然环境中研究整个线粒体群体提供了机会，在本研究中，我们研究了K(ATP)通道开放剂吡那地尔和二氮嗪对大鼠心脏线粒体原位呼吸速率的影响，该线粒体氧化生理底物丙酮酸和苹果酸（6+6 mM）。通过Clark型氧电极在生理盐溶液（37℃）中记录呼吸速率。我们的结果表明，吡那地尔和二氮嗪（60-1250μM）均以浓度依赖性方式使透皮心脏纤维的丙酮酸-苹果酸支持的状态2呼吸速率（59.1±5.1 nmol O/分钟/毫克纤维干重，RCI 2.6±0.2，n = 4）提高了15-120%。此外，二氮嗪不影响，而吡那地尔（60-1250μM）使透皮心脏纤维的状态3呼吸速率（116.6±13.6 nmol O/分钟/毫克纤维干重，RCI 2.3±0.2，n = 4）降低了4-27%。因此，两种K(ATP)通道开放剂的共同作用是使透皮心脏纤维中丙酮酸和苹果酸氧化的线粒体解偶联，而吡那地尔在相同条件下也抑制线粒体呼吸链。由于原位线粒体在很大程度上类似于体内线粒体，我们的结果表明解偶联和/或呼吸链抑制可能在K(ATP)通道开放剂的心脏保护中起作用。
