Studies of energy transport in heart cells: The effect of creatine phosphate on the frog ventricular contractile force and action potential duration

The effect of creatine phosphate on the contractile force and action-potential duration has been investigated using contracting frog ventricular preparation perfused with Ringer's solution. Creatine phosphate in concentrations of 10 m m and 20 m m enhanced both the force of contraction and action-potential duration, which returned to their normal value after the washout of creatine phosphate excess from the heart muscle. Significantly increased creatine-phosphate concentration in the perfusate (70 m m) initially caused an increase in both the force of contraction and action-potential duration followed by a spontaneous decrease of the contractile force which was increased again within the first minutes of creatine phosphate washout. However, during perfusion with creatine phosphate (70 m m) action-potential duration increased monotonically. These data are taken to indicate the existence of two different sites of creatine phosphate action in heart cells: on myofibrils and on the surface membrane of the cell. Changes in action-potential duration may be observed also after prolonged perfusion of heart strips with normal Ringer's solution and during subsequent perfusion with creatine solution. Perfusion of frog heart strips for 8 hr does not damage the ultrastructure of heart cells and does not lead to the depletion of their glycogen content. It has been shown that 1-fluoro 2 4-dinitrobenzene, often used for creatine phosphokinase inibition in intact tissue, inhibits both the force of contraction and action potential. The experimental results obtained support the concept of energy transport via creatine-phosphate pathway in heart cells and demonstrate the important role of creatine phosphate in regulation of heart muscle contraction.