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首页> 外文期刊>Canadian Journal of Physiology and Pharmacology >Caffeine and length dependence of staircase potentiation in skeletal muscle.
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Caffeine and length dependence of staircase potentiation in skeletal muscle.

机译：咖啡因和骨骼肌中楼梯增强的长度依赖性。

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Skeletal muscle sensitivity to Ca2+ is greater at long lengths, and this results in an optimal length for twitch contractions that is longer than optimal length for tetanic contractions. Caffeine abolishes this length dependence of Ca2+ sensitivity. Muscle length (ML) also affects the degree of staircase potentiation. Since staircase potentiation is apparently caused by an increased Ca2+ sensitivity of the myofilaments, we tested the hypothesis that caffeine depresses the length dependence of staircase potentiation. In situ isometric twitch contractions of rat gastrocnemius muscle before and after 10 s of 10-Hz stimulation were analyzed at seven different lengths to evaluate the length dependence of staircase potentiation. In the absence of caffeine, length dependence of Ca2+ sensitivity was observed, and the degree of potentiation after 10-Hz stimulation showed a linear decrease with increased length (DT = 1.47 - 0.05 ML, r2 = 0.95, where DT is developed tension). Length dependence of Ca2+ sensitivity was decreased by caffeine when caffeine was administered in amounts estimated to result in 0.5 and 0.75 mM concentrations. Furthermore, the negative slope of the relationship between staircase potentiation and muscle length was diminished at the lower caffeine dose, and the slope was not different from zero after the higher dose (DT = 1.53 - 0.009 ML, r2 = 0.43). Our study shows that length dependence of Ca2+ sensitivity in intact skeletal muscle is diminished by caffeine. Caffeine also suppressed the length dependence of staircase potentiation, suggesting that the mechanism of this length dependence may be closely related to the mechanism for length dependence of Ca2+ sensitivity.
机译：骨骼肌对Ca2 +的敏感性在较长的长度上更大，这导致抽搐收缩的最佳长度比破伤风收缩的最佳长度更长。咖啡因消除了Ca2 +敏感性的这种长度依赖性。肌肉长度（ML）也影响楼梯的增强程度。由于楼梯增强作用显然是由肌丝的Ca2 +敏感性增加引起的，因此我们测试了咖啡因抑制楼梯增强作用的长度依赖性的假说。在七个不同的长度上分析了10 Hz刺激10 s前后大鼠腓肠肌的等距抽搐收缩，以评估阶梯电位的长度依赖性。在不存在咖啡因的情况下，观察到了Ca2 +敏感性的长度依赖性，并且10 Hz刺激后的增强程度随长度增加呈线性下降（DT = 1.47-0.05 ML，r2 = 0.95，其中DT产生张力）。当咖啡因的施用量估计导致0.5和0.75 mM浓度时，咖啡因降低了Ca2 +敏感性的长度依赖性。此外，在较低的咖啡因剂量下，阶梯电位增强与肌肉长度之间的关系的负斜率减小，并且在较高的剂量后（DT = 1.53-0.009 ML，r2 = 0.43），该斜率与零无差异。我们的研究表明，咖啡因可降低骨骼肌中Ca2 +敏感性的长度依赖性。咖啡因还抑制了阶梯电位增强的长度依赖性，提示这种长度依赖性的机制可能与Ca2 +敏感性的长度依赖性机制密切相关。

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