Division of Cardiothoracic Surgery, Department of Surgery (M.M.A., E.M.K., C.M.M., A.D.K., R.B.S., J.S.L.) and Departments of Cell Biology and Physiology (H.Z., C.G.N.), Washington University School of Medicine, St. Louis, MO.
Circulation. 2013 Sep 10;128(11 Suppl 1):S130-5. doi: 10.1161/CIRCULATIONAHA.112.000128.
Cardiac myocytes demonstrate significant swelling and associated reduced contractility in response to stress that is prevented by the ATP-sensitive potassium channel opener, diazoxide (DZX) via an unknown mechanism. One proposed mechanism of cardioprotection is mitochondrial matrix swelling. To establish the relationship between mitochondrial and cellular volume during stress, this study examined the effect of DZX on mitochondrial volume.
Isolated mouse mitochondria were exposed to the following solutions: Tyrode, isolation buffer, cardioplegia (CPG)±DZX±ATP-sensitive potassium channel inhibitor, 5-hydroxydecanoate, and metabolic inhibition (MI) ± DZX ± 5-hydroxydecanoate. Mitochondrial volume was measured. DZX resulted in significant mitochondrial swelling (P<0.0001 versus Tyrode). MI and CPG resulted in significant mitochondrial swelling compared with baseline volume. The addition of DZX did not alter the response of mitochondrial volume to CPG (P=0.912) but increased swelling in response to MI (P=0.036). The addition of 5-hydroxydecanoate to MI + DZX or CPG+DZX significantly reduced mitochondrial swelling (P<0.003 MI+DZX versus MI + DZX + 5HD; P<0.001 CPG+DZX versus CPG + DZX + 5HD).
Both cellular and mitochondrial volume increased during exposure to MI and CPG. DZX did not alter mitochondrial volume during CPG; however, it was associated with an increase in mitochondrial volume during MI. 5-Hydroxydecanoate reduced mitochondrial volume during exposure to both stresses with DZX, supporting a role for a mitochondrial ATP-sensitive potassium channel in the mechanism of cardioprotection by DZX.
心肌细胞在应激时会发生显著肿胀，并伴有收缩力降低，这一现象可被三磷酸腺苷敏感性钾通道开放剂二氮嗪（DZX）所阻止，但具体机制尚不清楚。一种被提出的心肌保护机制是线粒体基质肿胀。为了确定应激过程中线粒体和细胞体积之间的关系，本研究检测了 DZX 对线粒体体积的影响。
分离的小鼠线粒体暴露于以下溶液中：Tyrode、分离缓冲液、心脏停搏液（CPG）±DZX±三磷酸腺苷敏感性钾通道抑制剂 5-羟基癸酸、代谢抑制（MI）±DZX±5-羟基癸酸。测量线粒体体积。DZX 导致线粒体显著肿胀（P<0.0001 与 Tyrode 相比）。MI 和 CPG 与基础体积相比导致线粒体肿胀显著增加。DZX 的添加并没有改变线粒体体积对 CPG 的反应（P=0.912），但增加了对 MI 的肿胀反应（P=0.036）。在 MI+DZX 或 CPG+DZX 中加入 5-羟基癸酸显著降低线粒体肿胀（P<0.003 MI+DZX 与 MI+DZX+5HD 相比；P<0.001 CPG+DZX 与 CPG+DZX+5HD 相比）。
MI 和 CPG 暴露期间，细胞和线粒体体积均增加。DZX 在 CPG 期间不会改变线粒体体积；然而，它与 MI 期间线粒体体积的增加有关。5-羟基癸酸降低了暴露于两种应激源时的线粒体体积，这支持了线粒体三磷酸腺苷敏感性钾通道在 DZX 心肌保护机制中的作用。
