Nonlinear relation between Vmax and INa in canine cardiac Purkinje cells.

摘要: We studied the relation of maximal upstroke velocity (Vmax) action potentials to peak sodium current (INa) under voltage clamp in single, internally perfused, canine cardiac Purkinje cells conditions that ensured membrane due only INa. Three different methods altering channel availability were investigated: voltage-dependent inactivation, tetrodotoxin (TTX) block, and use-dependent block by quinidine. Under all three conditions, Vmax INa was nonlinear, no found would allow prediction results from measurements. With inactivation or TTX measured reduced less than INa, so overestimated availability. This overestimation could be attributed greater mobilization during slowed potential upstrokes. The varied with experimental temperature as a consequence changes kinetics. also exposure Kd for 4.5 micron measurements but 1.6 microM Use-dependent quinidine had striking component not appreciated potentials. Consequently, underestimated conclude represent convenient index is reliable method quantitative studies behavior.