Okabe E, Kato Y, Sasaki H, Saito G, Hess M L, Ito H
Arch Biochem Biophys. 1987 Jun;255(2):464-8. doi: 10.1016/0003-9861(87)90416-4.
The effect of scavengers of oxygen radicals on canine cardiac sarcoplasmic reticulum (SR) Ca2+ uptake velocity was investigated at pH 6.4, the intracellular pH of the ischemic myocardium. With the generation of oxygen radicals from a xanthine-xanthine oxidase reaction, there was a significant depression of SR Ca2+ uptake velocity. Xanthine alone or xanthine plus denatured xanthine oxidase had no effect on this system. Superoxide dismutase (SOD), a scavenger of .O2-, or denatured SOD had no effect on the depression of Ca2+ uptake velocity induced by the xanthine-xanthine oxidase reaction. However, catalase, which can impair hydroxyl radical (.OH) formation by destroying the precursor H2O2, significantly inhibited the effect of the xanthine-xanthine oxidase reaction. This effect of catalase was enhanced by SOD, but not by denatured SOD. Dimethyl sulfoxide (Me2SO), a known .OH scavenger, completely inhibited the effect of the xanthine-xanthine oxidase reaction. The observed effect of oxygen radicals and radical scavengers was not seen in the calmodulin-depleted SR vesicles. Addition of exogenous calmodulin, however, reproduced the effect of oxygen radicals and the scavengers. The effect of oxygen radicals was enhanced by the calmodulin antagonists (compounds 48/80 and W-7) at concentrations which showed no effect alone on Ca2+ uptake velocity. Taken together, these findings strongly suggest that .OH, but not .O2-, is involved in a mechanism that may cause SR dysfunction, and that the effect of oxygen radicals is calmodulin dependent.
在缺血心肌细胞内pH值6.4的条件下，研究了氧自由基清除剂对犬心肌肌浆网（SR）Ca2+摄取速度的影响。通过黄嘌呤-黄嘌呤氧化酶反应产生氧自由基时，SR Ca2+摄取速度显著降低。单独的黄嘌呤或黄嘌呤加变性黄嘌呤氧化酶对该系统无影响。超氧化物歧化酶（SOD），一种.O2-的清除剂，或变性SOD对黄嘌呤-黄嘌呤氧化酶反应诱导的Ca2+摄取速度降低无影响。然而，过氧化氢酶可通过破坏前体H2O2来抑制羟自由基（.OH）的形成，它能显著抑制黄嘌呤-黄嘌呤氧化酶反应的作用。SOD可增强过氧化氢酶的这种作用，但变性SOD则不能。二甲基亚砜（Me2SO），一种已知的.OH清除剂，可完全抑制黄嘌呤-黄嘌呤氧化酶反应的作用。在钙调蛋白缺失的SR囊泡中未观察到氧自由基和自由基清除剂的上述作用。然而，添加外源性钙调蛋白可重现氧自由基和清除剂的作用。钙调蛋白拮抗剂（化合物48/80和W-7）在单独对Ca2+摄取速度无影响的浓度下可增强氧自由基的作用。综上所述，这些发现强烈表明，参与可能导致SR功能障碍机制的是.OH而非.O2-，并且氧自由基的作用依赖于钙调蛋白。
