Slow inward calcium currents have no obvious role in muscle excitation–contraction coupling

摘要: It has been proposed1 that an influx of calcium ions into twitch muscle fibres during action potential might initiate contraction. However, when external Ca2+ is lowered to 10−8 M with EGTA, the can produce normal twitches for many minutes2,3. Nevertheless, a clear contraction demonstrated4,5, and it found phasic skeletal inward current (ICa)6,7 which give rise spikes8. In certain conditions, reduction in 80–90 mM EGTA results reversible blockade excitation–contraction (e–c) coupling9, leading some authors suggest7,9–11 extracellular moved myoplasm due ICa may be involved e–c coupling mechanism triggers This proposition was further supported by localization T-system, circumvented problem delay diffusion from surface membrane. We have now investigated whether role initiating or sustaining contractions fibres. Our approach decrease eliminate calcium-blocking agent diltiazem (Herbesser) see how twitch, tetanic potassium-contracture tensions were affected. could decreased cancelled agent, but same concentration drug potentiated tetanus contractures. conclude, therefore, no coupling. A preliminary report these presented elsewhere12.