pH변화가 심실근 경축현상에 미치는 영향

Abstract

Potassium contractures were induced in isolated frog(Rana tcmporaria) ventricular strips with trisbuffered Ringer solutions containing 20~100mM K ions and concomitantly less Na ions at room temperaturet lS to 20nC). External pH was raised up to 8.4 or lowered down to 6.4 and its effect upon K-contracture was investigated to elicit the mechanism of action of H ions on excitation-contraction coupling in frog ventricular myocardium. Followings are the results obtained: ]. At normal pH, biphasic contracture was evoked at external K concentration of 40mM. On rasing K concentration to lOOmM, contracture tension increased gradually and the interval between the end of contracture and resuming of twitch was also prolonged. When K-20mM solution was replaced by normal Ringer solution, twitch tension developed rapidly and much higher tension than control twitch was elicited transiently. After the first application of K-100mM fully recovered tensions were always smaller than those of control twitch tensions. 2. On raising external pH from normal to 8.4, there were no significant changes in K-induced contractures comparing to those evoked under normal pH. 3. On lowering external pH down to 7.4, phasic portion of K-contractures were augmented within the range of 20 to 40mM K and tonic portions in creased gradually with time elapsed at 100mM K ion concentrations. From the above results it was concluded that H ion acted upon contracture induced by high K with low Na ion" Via the inhibition of Na-K pump during the early phase and changes in intracellular pII during the later phase.