The Effect of Lithium on Strophanthidin Toxicity in Cardiac Purkinje Fibers 1

Summary

The effect of lithium (5 mM) on strophanthidin-induced spontaneous activity was studied in canine Purkinje fibers perfused in vitro. Lithium did not alter the configuration of the action potential and had little effect on contractile force. Strophanthidin induced the usual increase and then a decrease in contractile force and eventually spontaneous activity. Lithium modified little the effect of strophanthidin on force but spontaneous activity occurred sooner. Catecholamines are stored in Purkinje fibers but these stores are unimportant in the facilitatory action of lithium on digitalis toxicity, since lithium did not increase the effects of exogenous norepinephrine, either in the absence or in the presence of strophanthidin. It is concluded that lithium favors (and does not antagonize) the onset of digitalis-induced spontaneous activity and this action does not involve a change in cardiac catecholamine metabolism.