Sharikabad Mohammad Nouri, Aronsen Jan Magnus, Haugen Espen, Pedersen Janne, Møller Anne-Sophie W, Mørk Halvor Kjeang, Aass Hans C D, Sejersted Ole M, Sjaastad Ivar, Brørs Odd
Dept. of Clinical Chemistry, Ullevål Univ. Hopital, 0407 Oslo, Norway.
Am J Physiol Heart Circ Physiol. 2009 Mar;296(3):H787-95. doi: 10.1152/ajpheart.00796.2008. Epub 2009 Jan 9.
Altered myocardial Ca(2+) and Na(+) handling in congestive heart failure (CHF) may be expected to decrease the tolerance to ischemia by augmenting reperfusion Ca(2+) overload. The aim of the present study was to investigate tolerance to hypoxia-reoxygenation by measuring enzyme release, cell death, ATP level, and cell Ca(2+) and Na(+) in cardiomyocytes from failing rat hearts. CHF was induced in Wistar rats by ligation of the left coronary artery during isoflurane anesthesia, after which cardiac failure developed within 6 wk. Isolated cardiomyocytes were cultured for 24 h and subsequently exposed to 4 h of hypoxia and 2 h of reoxygenation. Cell damage was measured as lactate dehydrogenase (LD) release, cell death as propidium iodide uptake, and ATP by firefly luciferase assay. Cell Ca(2+) and Na(+) were determined with radioactive isotopes, and free intracellular Ca(2+) concentration (Ca(2+)) with fluo-3 AM. CHF cells showed less increase in LD release and cell death after hypoxia-reoxygenation and had less relative reduction in ATP level after hypoxia than sham cells. CHF cells accumulated less Na(+) than sham cells during hypoxia (117 vs. 267 nmol/mg protein). CHF cells maintained much lower Ca(2+) than sham cells during hypoxia (423 vs. 1,766 arbitrary units at 4 h of hypoxia), and exchangeable Ca(2+) increased much less in CHF than in sham cells (1.4 vs. 6.7 nmol/mg protein) after 120 min of reoxygenation. Ranolazine, an inhibitor of late Na(+) current, significantly attenuated both the increase in exchangeable Ca(2+) and the increase in LD release in sham cells after reoxygenation. This supports the suggestion that differences in Na(+) accumulation during hypoxia cause the observed differences in Ca(2+) accumulation during reoxygenation. Tolerance to hypoxia and reoxygenation was surprisingly higher in CHF than in sham cardiomyocytes, probably explained by lower hypoxia-mediated Na(+) accumulation and subsequent lower Ca(2+) accumulation in CHF after reoxygenation.
充血性心力衰竭（CHF）中心肌钙（Ca2+）和钠（Na+）处理的改变，可能会因再灌注钙超载增加而降低对缺血的耐受性。本研究的目的是通过测量衰竭大鼠心脏心肌细胞中的酶释放、细胞死亡、ATP水平以及细胞钙（Ca2+）和钠（Na+），来研究对缺氧-复氧的耐受性。在异氟烷麻醉期间，通过结扎左冠状动脉在Wistar大鼠中诱导CHF，此后在6周内出现心力衰竭。分离的心肌细胞培养24小时，随后暴露于4小时缺氧和2小时复氧。细胞损伤以乳酸脱氢酶（LD）释放来衡量，细胞死亡以碘化丙啶摄取来衡量，ATP通过萤火虫荧光素酶测定法来测定。细胞钙（Ca2+）和钠（Na+）用放射性同位素测定，细胞内游离钙（Ca2+）浓度（[Ca2+]i）用Fluo-3 AM测定。与假手术组细胞相比，CHF细胞在缺氧-复氧后LD释放和细胞死亡的增加较少，并且在缺氧后ATP水平的相对降低也较少。在缺氧期间，CHF细胞比假手术组细胞积累的钠（Na+）更少（117对267 nmol/mg蛋白质）。在缺氧期间，CHF细胞维持的[Ca2+]i比假手术组细胞低得多（在缺氧4小时时为423对1766任意单位），并且在复氧120分钟后，CHF细胞中可交换钙（Ca2+）的增加比假手术组细胞少得多（1.4对6.7 nmol/mg蛋白质）。雷诺嗪是一种晚期钠电流抑制剂，在复氧后可显著减弱假手术组细胞中可交换钙（Ca2+）的增加和LD释放的增加。这支持了以下观点，即缺氧期间钠（Na+）积累的差异导致了复氧期间观察到的钙（Ca2+）积累的差异。令人惊讶的是，CHF心肌细胞对缺氧和复氧的耐受性高于假手术组心肌细胞，这可能是由于CHF中缺氧介导的钠（Na+）积累较低，以及复氧后随后的钙（Ca2+）积累较低所致。
