Raymond G, Potreau D, Cognard C, Jacquenod J C, Poindessault J P
Can J Physiol Pharmacol. 1987 Apr;65(4):704-10. doi: 10.1139/y87-116.
The effect of stimulation rate and of external ionic composition on the repriming period of contractures induced by 6 mM caffeine was tested on isolated skeletal muscle fibres of the frog (Rana ridibunda). The repriming period, which was 11.2 +/- 0.1 min (mean +/- SEM, n = 9) on quiescent fibres, was shortened in fibres stimulated at a frequency ranging from 3 to 12 min-1 (optimal rate, 8 min-1; full repriming 5.7 +/- 0.2 min; n = 10). A 10-fold increase in the extracellular calcium concentration shortened the repriming period on both stimulated and quiescent fibres, whereas decreasing external calcium (1/10) delayed it. In a Na+-free solution (Li+ substituted) the repriming period of stimulated fibres was markedly delayed (14 min), whereas quiescent fibres never recover more than 10% of their ability to develop subsequent caffeine contractures. In contrast, with a 35% Na solution, the repriming period was greatly shortened (stimulated, 5.4 +/- 0.2 min, n = 7; quiescent, 6.2 +/- 0.5 min, n = 8). It is concluded that repriming depends on three mechanisms that seem to refill a calcium store and trigger recovery: the slow inward calcium current, a Na+-Ca2+ exchange, and perhaps a passive Ca2 influx.
在青蛙（泽蛙）的离体骨骼肌纤维上，测试了刺激频率和外部离子组成对6 mM咖啡因诱导的挛缩再激发期的影响。静息纤维的再激发期为11.2±0.1分钟（平均值±标准误，n = 9），在以3至12分钟-1的频率刺激的纤维中再激发期缩短（最佳频率为8分钟-1；完全再激发为5.7±0.2分钟；n = 10）。细胞外钙浓度增加10倍会缩短刺激纤维和静息纤维的再激发期，而降低外部钙浓度（降至1/10）则会延迟再激发期。在无钠溶液（用锂替代）中，刺激纤维的再激发期明显延迟（14分钟），而静息纤维随后产生咖啡因挛缩的能力恢复从未超过10%。相反，在35%的钠溶液中，再激发期大大缩短（刺激纤维，5.4±0.2分钟，n = 7；静息纤维，6.2±0.5分钟，n = 8）。结论是，再激发取决于三种机制，这三种机制似乎是对钙储存进行再填充并触发恢复：缓慢内向钙电流、钠-钙交换，可能还有被动钙内流。
