Relaxation in Skeletal Muscle

从皮肤纤维和分离蛋白质的研究中得出的放松模型最终必须在完整的肌肉上进行测试。本提案的目的是测量与(i) Ca2+int和（ii）交叉桥相互调节相关的事件之间的关系。连接桥的比例滞后于Ca2+int的下降和完整细胞的松弛。交叉桥连接本身可能会减缓放松（Weber和Murray， 1973）。长度的快速变化导致心肌和藤条肌中出现额外的Ca2+int (Ridgeway和Gordon， 1984)，但在脊椎动物骨骼肌中没有（Fuchs和Wang， 1991）。快速长度变化将应用于注射水镁素的青蛙骨骼肌，以探索(i) Ca2+int, （ii）松弛率，（iii）刚度，（iv）纤维重叠和(v)激活程度之间的关系（Cecchi等人，1986）。结果将完善肌肉松弛机制可感知的概念不止一种。双重调节机制的生理重要性将被确定，Ca2+int和交叉桥在相互调节中的相对贡献将被定义。

Models of relaxing derived from studies on skinned fibers and isolated proteins must ultimately be tested on intact muscle. The aim of this proposal is to measure relationships among events connected with reciprocal regulation by (i) Ca2+int and (ii) cross- bridges. The fraction of attached bridges lags behind the fall in Ca2+int and relaxation in intact cells. Cross-bridge attachment itself may slow relaxation (Weber and Murray, 1973). Quick length changes cause the appearance of extra Ca2+int in cardiac and barnacle muscle (Ridgeway and Gordon, 1984), but not in vertebrate skeletal muscle (Fuchs and Wang, 1991). Quick length changes will be applied to aequorin-injected frog skeletal muscle to probe the relations among (i) Ca2+int, (ii) rate of relaxation, (iii) stiffness, (iv) filament overlap, and (v) degree of activation (Cecchi et al., 1986) The results will refine the concept that mechanisms underlying g muscle relaxation are perceivably of more than one kind. The physiological importance of dual regulatory mechanisms will be determined and the relative contribution of Ca2+int and cross-bridges in reciprocal regulation will be defined.