망간 이온이 개구리 심방근의 막전압 및 수축력에 미치는 영향

Abstract

The effect of manganese ion on transmembrane potential and tension of the atrial strip was studied in the frog. Manganese (l~8 mM) suppressed the plateau resulting in a shortening of action potential duration. The change was a function of time and during the first 5 minutes the action potential duration increased, then it gradually shortened. Although resting membrane was more or less hyperpolarized, there was no significant changes in the amplitnde of action potential and resulted in an increased overshoot potential. In all the experiments the contractile tension of atrial muscle superfused with Mn-Ringer decreased consistently as the concentration of manganese increased. But 10 to 20% of relative tension to that of control persisted even at 8 mM Mn-Ringer for more than half an hour. Manganese elevated the threshold of atrial contraction and reduced the conduction velocity. The above results suggested that manganese not only altered the transmembrane potential but also acted on the excitation-contraction coupling to produce a decrease in tension.