Busselen P
Pflugers Arch. 1987 May;408(5):458-64. doi: 10.1007/BF00585069.
Reduction of the Na concentration in the Ca-free perfusion solution reduces the amount of myoglobin released by the cells when Ca is readmitted if sucrose is used to replace NaCl under mild hypothermia. When salts like cholinechloride or LiCl are used instead of sucrose, no protection is seen at any temperature. The temperature threshold above which myoglobin loss sharply increases is lowered by prolonged Ca depletion or by the addition of EGTA to the Ca-free solution. Protection by sucrose does not occur in the presence of EGTA. An increase of cell Na induced by strophanthidin during the Ca depletion phase has no effect on myoglobin release. The exponential decline in twitch tension in the early phase of Ca deprivation has the same half-live (T1/2) for Ca-free solutions containing 145 mM Na or 35 mM Na (110 mM Li or choline), but its T1/2 is prolonged if sucrose is used to replace NaCl. When 5 mM EGTA is added to the Ca-free solutions, the T1/2 is shortened and is not changed by the replacement of NaCl with sucrose. The rate of washout of Ca within the first 20 s of Ca depletion has a similar time course in a normal Na or in a Li and low Na solution. In a sucrose and low Na solution the rate of the Ca efflux is reduced. The addition of EGTA increases this rate and abolishes the slowing effect of a sucrose and low Na solution. Therefore myoglobin release during the Ca paradox does not depend on the Na gradient across the sarcolemma.(ABSTRACT TRUNCATED AT 250 WORDS)
在轻度低温条件下，如果用蔗糖替代氯化钠，降低无钙灌注溶液中的钠浓度可减少重新加入钙时细胞释放的肌红蛋白量。当使用氯化胆碱或氯化锂等盐类替代蔗糖时，在任何温度下均未观察到保护作用。长时间的钙缺失或向无钙溶液中添加乙二醇双四乙酸（EGTA）会降低肌红蛋白损失急剧增加的温度阈值。在EGTA存在的情况下，蔗糖不会产生保护作用。在钙缺失阶段，毒毛花苷诱导的细胞内钠增加对肌红蛋白释放没有影响。在无钙溶液中，含有145 mM钠或35 mM钠（110 mM锂或胆碱）时，钙剥夺早期抽搐张力的指数下降具有相同的半衰期（T1/2），但如果用蔗糖替代氯化钠，其T1/2会延长。当向无钙溶液中添加5 mM EGTA时，T1/2缩短，且用蔗糖替代氯化钠不会改变T1/2。在正常钠溶液或锂和低钠溶液中，钙剥夺最初20秒内钙的洗脱速率具有相似的时间进程。在蔗糖和低钠溶液中，钙外流速率降低。添加EGTA可增加该速率，并消除蔗糖和低钠溶液的减缓作用。因此，钙反常期间的肌红蛋白释放不依赖于跨肌膜的钠梯度。（摘要截短于250字）
