Bittar E E, Xiang Z, Huang Y P
Department of Physiology, University of Wisconsin, Madison 53706.
Biochim Biophys Acta. 1992 Jul 27;1108(2):210-4. doi: 10.1016/0005-2736(92)90027-j.
The injection of citrate produces considerably greater stimulation of the Na efflux in ouabain-poisoned fibers (from the barnacle Balanus nubilus) than in unpoisoned fibers. When injected in excess together with Al into unpoisoned fibers it is without effect. Its injection is also without effect on the decline in the Na efflux elicited by injecting Al beforehand. Citrate injection into ouabain-poisoned fibers following peak stimulation by injecting Al produces a further rise which is a function of the Al concentration. Al injection after peak stimulation of the ouabain-insensitive Na efflux by citrate is usually without significant effect. Injection of aspartate into poisoned fibers causes a small rise in the remaining Na efflux and fails to prevent the response to Al injection from occurring. Taken together, these observations are in keeping with the view that citrate is not only a powerful chelator of Al but also a powerful activator of reverse Na+/Ca2+ exchange in ouabain-poisoned fibers, presumably because of its ability to raise myoplasmic pMg.
与未中毒的纤维相比，柠檬酸盐注射对哇巴因中毒的纤维（来自藤壶巴氏藤壶）中钠外流的刺激作用要大得多。当与铝一起过量注射到未中毒的纤维中时，它没有效果。其注射对预先注射铝引起的钠外流下降也没有影响。在铝引起的峰值刺激后，向哇巴因中毒的纤维中注射柠檬酸盐会导致进一步升高，这是铝浓度的函数。在柠檬酸盐对哇巴因不敏感的钠外流进行峰值刺激后注射铝通常没有显著影响。向中毒的纤维中注射天冬氨酸会使剩余的钠外流略有增加，并且不能阻止对铝注射的反应发生。综上所述，这些观察结果与以下观点一致：柠檬酸盐不仅是铝的强大螯合剂，而且是哇巴因中毒纤维中反向钠/钙交换的强大激活剂，大概是因为它能够提高肌浆中的镁离子浓度。
