Xie Z J, Wang Y H, Askari A, Huang W H, Klaunig J E, Askari A
Department of Pharmacology, Medical College of Ohio, Toledo, OH 43699-0008.
J Mol Cell Cardiol. 1990 Aug;22(8):911-20. doi: 10.1016/0022-2828(90)90122-i.
Isolated myocytes of rat heart, and sealed sarcolemmal vesicles of bovine heart, were used to examine the selectivity of the effects of partially reduced oxygen species (generated by a mixture of xanthine and xanthine oxidase) on cardiac sodium pump and several other ion transporters of the plasma membrane. When myocytes were exposed to xanthine plus xanthine oxidase, there were time-dependent inhibitions of ouabain-sensitive 86Rb+ uptake and (Na+ + K+)-ATPase activity that could be prevented by allopurinol, or by catalase and superoxide dismutase; suggesting the involvements of H2O2 or oxygen free radicals in the inhibition of the pump. This inhibition preceded any significant decrease in cellular ATP or in the number of viable cells. While ouabain increased 45Ca2+ uptake by myocytes as expected, exposure to xanthine plus xanthine oxidase decreased 45Ca2+ uptake; suggesting that the Na+, Ca2(+)-exchanger of the intact myocytes is also inhibited by oxygen metabolites. Simultaneous inhibitions of the pump, the Na+, Ca2(+)-exchange, the Na+, H(+)-exchange, and the Na+, Pi-cotransport activities also occurred in sarcolemmal vesicles that were treated with xanthine plus xanthine oxidase. These findings indicate that inactivations of the sodium pump and other sarcolemmal ion carriers are early events in the oxidant-induced damage to the cardiomyocyte. In the rat heart myocytes, a fraction of (Na+ + K+)-ATPase that seems to be more sensitive to ouabain, was inactivated more rapidly upon exposure of myocytes to xanthine plus xanthine oxidase; raising the possibility of the existence of different pump populations with different sensitivities to extracellularly generated oxygen metabolites.
采用大鼠心脏的分离心肌细胞和牛心脏的封闭肌膜囊泡，研究部分还原氧物种（由黄嘌呤和黄嘌呤氧化酶混合物产生）对心脏钠泵及质膜上其他几种离子转运体作用的选择性。当心肌细胞暴露于黄嘌呤加黄嘌呤氧化酶时，哇巴因敏感的⁸⁶Rb⁺摄取和（Na⁺ + K⁺）-ATP酶活性出现时间依赖性抑制，这种抑制可被别嘌呤醇、过氧化氢酶和超氧化物歧化酶阻止；提示H₂O₂或氧自由基参与了对泵的抑制作用。这种抑制在细胞ATP或活细胞数量显著减少之前就已出现。正如预期的那样，哇巴因增加了心肌细胞对⁴⁵Ca²⁺的摄取，而暴露于黄嘌呤加黄嘌呤氧化酶则降低了⁴⁵Ca²⁺的摄取；表明完整心肌细胞的Na⁺，Ca²⁺交换体也受到氧代谢产物的抑制。在用黄嘌呤加黄嘌呤氧化酶处理的肌膜囊泡中，泵、Na⁺，Ca²⁺交换、Na⁺，H⁺交换和Na⁺，Pi共转运活性也同时受到抑制。这些发现表明，钠泵和其他肌膜离子载体的失活是氧化剂诱导心肌细胞损伤的早期事件。在大鼠心脏心肌细胞中，一部分似乎对哇巴因更敏感的（Na⁺ + K⁺）-ATP酶，在心肌细胞暴露于黄嘌呤加黄嘌呤氧化酶后更快失活；增加了存在对细胞外产生的氧代谢产物敏感性不同的不同泵群体的可能性。
