The Effect of Digitalis (Cedilanid) on the Mechanical and Electrical Activity of Extracted and Nonextracted Heart Muscle Preparations

The purpose of this investigation was to study the effect of Cedilanid on the mechanical and electrical activity of extracted and nonextracted heart muscle strips of dogs. The glycoside did not influence the work, the speed of contraction, or the length–resting tension relationship of extracted heart muscle. It produced changes in membrane action potentials, but none in membrane resting potentials. The problem of whether digitalis is bound to the membrane or the cell protein was investigated by temporary destruction of the cell membrane by water. The effects of cardiac glycosides on contractile proteins and on membrane activity are probably inseparable; they act through changes in ionic gradient between muscle cells and the surrounding medium.