Siegmund B, Schlack W, Ladilov Y V, Balser C, Piper H M
Physiologisches Institut, Justus-Liebig-Universität, Giessen, Germany.
Circulation. 1997 Dec 16;96(12):4372-9. doi: 10.1161/01.cir.96.12.4372.
Resupply of oxygen to the myocardium after extended periods of ischemia or hypoxia can rapidly aggravate the already existing injury by provoking hypercontracture of cardiomyocytes (acute reperfusion injury). Previous studies indicated that halothane can protect ischemic-reperfused myocardium. The aim of the present study was to analyze on the cellular level the mechanism by which halothane may protect against reoxygenation-induced hypercontracture.
To simulate ischemia-reperfusion, isolated adult rat cardiomyocytes were incubated at pH 6.4 under anoxia and reoxygenated at pH 7.4 in the presence or absence of 0.4 mmol/L halothane. Reoxygenation was started when intracellular Ca2+ (measured with fura 2) had increased to > or = 10(-5) mol/L and pHi (BCECF) had decreased to 6.5. Development of hypercontracture was determined microscopically. In the control group, reoxygenation provoked oscillations of cytosolic Ca2+ (72+/-9 per minute at fourth minute of reoxygenation) accompanied by development of hypercontracture (to 65+/-3% of end-ischemic cell length). When halothane was added on reoxygenation, Ca2+ oscillations were markedly reduced (4+/-2 per minute, P<.001) and hypercontracture was virtually abolished (90+/-4% of end-ischemic cell length, P<.001). Halothane did not influence the recovery of pHi during reoxygenation. Similar effects on Ca2+ oscillations and hypercontracture were observed when ryanodine (3 micromol/L), an inhibitor of the sarcoplasmic reticulum Ca2+ release, or cyclopiazonic acid (10 micromol/L), an inhibitor of the sarcoplasmic reticulum Ca2+ pump, were applied instead of halothane.
Halothane protects cardiomyocytes against reoxygenation-induced hypercontracture by preventing oscillations of intracellular Ca2+ during the early phase of reoxygenation.
在长时间缺血或缺氧后，心肌的氧再供应可通过引发心肌细胞的过度收缩（急性再灌注损伤）迅速加重已有的损伤。先前的研究表明，氟烷可保护缺血再灌注心肌。本研究的目的是在细胞水平上分析氟烷可能预防复氧诱导的过度收缩的机制。
为模拟缺血再灌注，将分离的成年大鼠心肌细胞在pH 6.4、缺氧条件下孵育，然后在有或无0.4 mmol/L氟烷存在的情况下于pH 7.4复氧。当细胞内Ca²⁺（用fura 2测量）增加至≥10⁻⁵ mol/L且细胞内pH（BCECF）降至6.5时开始复氧。通过显微镜观察过度收缩的发展情况。在对照组中，复氧引发胞质Ca²⁺振荡（复氧第4分钟时每分钟72±9次），同时伴有过度收缩的发展（达到缺血末期细胞长度的65±3%）。当复氧时加入氟烷，Ca²⁺振荡明显减少（每分钟4±2次，P<0.001），过度收缩几乎完全消除（缺血末期细胞长度的90±4%，P<0.001）。氟烷不影响复氧期间细胞内pH的恢复。当使用肌浆网Ca²⁺释放抑制剂ryanodine（3 μmol/L）或肌浆网Ca²⁺泵抑制剂环匹阿尼酸（10 μmol/L）代替氟烷时，观察到对Ca²⁺振荡和过度收缩有类似的影响。
氟烷通过在复氧早期防止细胞内Ca²⁺振荡来保护心肌细胞免受复氧诱导的过度收缩。
