Elektrophysiologische Studien zur Aufhebung der Kaliumlähmung des Froschmyokards durch ATP

Summary

The electrical and mechanical activity of an isolated frog's ventricle in Ringer solution paralyzed by rising the extracellular potassium concentration to 12.8 mM can be restored by addition of ATP as shown in earlier experiments.

Further information about the mechanism of action of ATP could be obtained by an analysis of the bioelectrical phenomena with intracellular electrodes and by isometrical tension measurements. In the high potassium Ringer solution the resting potential of the myocardial fibres was found to be reduced from the normal value of 69 (± 0.6) mV to a lower average amounting to 40 (± 0.5) mV. ATP on the other hand, when added to the paralyzing medium, led to a partial recovery of the membrane potential so that an average of 49 (± 0.6) mV was found. Furthermore the conductivity and the conduction velocity of the myocardial fibres could be restored. Simultaneously the shape of the action potential, which was heavily affected by high potassium, returned towards normal under the influence of ATP. This effect of ATP became particularly obvious in reestablishing the prolonged duration of the myocardial action potential (plateau). In general the membrane potential and the bioelectrical activity of the fibres did not return completely to the initial state. Nevertheless the recovery of the mechanical tension often exceeded the normal values found in usual Ringer solution. This observation may be indicative for another action of ATP on the electromechanical coupling at the membrane.