A Study of the Membrane Constants in the Dog Myocardium

Using the partition chamber method together with microelectrodes, membrane constants of the dog heart were determined in the pectinate muscle of the right atrium (A), false tendon (F) and papillary muscle of the right ventricle (V). The membrane capacity calculated from the time course of propagating action potential foot and propagation velocity was 2.6, 1.7 (6.8) and 0.6μEF/cm2 for A, F and V. The electrotonic potential and its spatial decline observed with the partition chamber conformed with the cable law. The space constant was 1.24mm for A, 1.25mm for F and 1.18mm for V. The time constants were 14.6, 15.0 and 3.2msec. The membrane resistance calculated from these values appeared about 5600, 8900 (2200) and 5300Ωcm2 for A, F and V respectively. The safety factor for excitation conduction was estimated to be 4.4, 7.6 and 2.0. Differences and agreements in value between the membrane constants determined by mass polarization and by intracellular polarization were discussed.