Reinvestigation of calcium release mechanism from the sarcoplasmic reticulum in cardiac excitation-contraction coupling.

It is generally believed that physiological contraction of mammalian cardiac muscle is mediated by CaイD12+イエD1 released from the sarcoplasmic reticulum （SR） by activation of CaイD12+イエD1 release mManagement ism（CICR） evoked by CaイD12+イエD1 entered from external medium during action potential。然而，由于CICR的抑制剂在我们的初步研究中没有出现被抑制的心脏病接触，我们研究了这个问题，我们获得了以下结果：1）在ATP的存在中，肾上腺素抑制的CICR也在心脏病肌肉中被抑制，以前在骨骼肌肉中被抑制。2）肾上腺素上升到10 mM没有在所有电子干扰的心脏病接触中被抑制，but only potentiated it slowly. 3） Adenine initially decreased but then slowly increased action potential-evoked CaイイD12+イエD1 transient。与洗涤腺苷D12+腺苷D1瞬态初始增加，然后减少到原始水平. 4）抑制了Cardiac Muscle的K-诱导接触。结果1）&2）注意到心脏接触的指示，心脏接触不是由CICR中介的，但对Caii D12+腺苷D1瞬态的直接影响，以及结果4）清楚地支持CICR理论。The apparent discrepancy may be Oracle ained by other effen of adenine， inhibition of CaイD12+イD1 uptake by SR and increase of CaイD12+イD1 sensitManagement of the contractile system。

It is generally believed that physiological contraction of mammalian cardiac muscle is mediated by CaィイD12+ィエD1 released from the sarcoplasmic reticulum (SR) by activation of CaィイD12+ィエD1 -induced CaィイD12+ィエD1 release mechanism (CICR) evoked by CaィイD12+ィエD1 entered from external medium during action potentials. However, since inhibitors of CICR appeared not to inhibit cardiac contraction in our preliminary studies, we examined this problem closely.We obtained the following results.1) In the presence of ATP, adenine inhibited CICR also in cardiac muscle as previously shown in Skeletal muscle.2) Adenine up to 10 mM did not inhibit at all electrically evoked cardiac contraction, but only potentiated it slowly.3) Adenine initially decreased but then slowly increased action potential-evoked CaィイD12+ィエD1 transient. Conversely on washing adenine CaィイD12+ィエD1 transient initially increased and then decreased to the original level.4) Procaine inhibited K-induced contraction of cardiac muscle.The results 1) & 2) appears to indicate that cardiac contraction is not mediated by CICR, but the immediate effect of adenine on CaィイD12+ィエD1 transient and the result 4) clearly support the CICR theory. The apparent discrepancy may be explained by other effects of adenine, inhibition of CaィイD12+ィエD1 uptake by SR and increase of CaィイD12+ィエD1 sensitivity of the contractile system.