Nosek T M, Williams M F, Zeigler S T, Godt R E
Am J Physiol. 1986 May;250(5 Pt 1):C807-11. doi: 10.1152/ajpcell.1986.250.5.C807.
Experiments from other laboratories suggest that inositol trisphosphate (InsP3) may be involved in the excitation-contraction coupling (ECC) process of cardiac and skeletal muscle. Our results support this hypothesis. Studying fiber bundles (less than 200-microns diameter) from guinea pig papillary muscles skinned with saponin and mechanically skinned single fibers from frog semitendinosus muscle, we find that calcium-induced force oscillations (observed in solutions containing low ethyleneglycol-bis(beta-aminoethylether)-N,N'-tetraacetic acid and pCa 7.0) are enhanced in magnitude and frequency by InsP3 at concentrations as low as 1 microM. InsP3 at 10 microM can often induce such oscillations in mechanically skinned frog skeletal muscle. In skinned cardiac fibers, InsP3 increases the magnitude of caffeine contractures at submaximal caffeine concentrations to a greater extent than at near-maximal caffeine concentrations. InsP3 (30 microM) has no effect on either the calcium sensitivity or maximal force generated by the contractile apparatus of skinned cardiac muscle. We conclude that InsP3 has no direct effect on the contractile machinery but that it can modulate ECC by enhancing the calcium-induced release of calcium from the sarcoplasmic reticulum, possibly from the same pool and through the same mechanism as caffeine.
其他实验室的实验表明，肌醇三磷酸（InsP3）可能参与心肌和骨骼肌的兴奋-收缩偶联（ECC）过程。我们的结果支持这一假设。通过研究用皂角苷去皮的豚鼠乳头肌纤维束（直径小于200微米）以及青蛙半腱肌的机械去皮单纤维，我们发现，在含有低浓度乙二醇双（β-氨基乙醚）-N，N'-四乙酸且pCa为7.0的溶液中观察到的钙诱导的力振荡，在低至1微摩尔浓度的InsP3作用下，其幅度和频率都会增强。10微摩尔浓度的InsP3常常能在机械去皮的青蛙骨骼肌中诱导出此类振荡。在去皮的心脏纤维中，InsP3在低于最大咖啡因浓度时比在接近最大咖啡因浓度时能更大程度地增加咖啡因挛缩的幅度。InsP3（30微摩尔）对去皮心肌收缩装置的钙敏感性或产生的最大力量均无影响。我们得出结论，InsP3对收缩机制没有直接影响，但它可以通过增强钙诱导的肌浆网钙释放来调节ECC，可能与咖啡因来自同一钙库并通过相同机制。
