Direct Effects of KATP Channel Openers Pinacidil and Diazoxide on Oxidative Phosphorylation of Mitochondria in situ

Cellular Physiology and Biochemistry

关键词: Mitochondria in situ;    Oxidative phosphorylation;    KATP channel openers;    Skinned cardiac fibers;    Pinacidil;    Diazoxide;    Uncoupling;   

DOI  :  10.1159/000276552

学科分类：分子生物学，细胞生物学和基因

来源: S Karger AG

【 摘 要 】

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°C). Our results showed that both pinacidil and diazoxide (60-1250 µM) 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 µM) 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.

【 授权许可】

CC BY-NC-ND