Effects of free radicals on Na(+)-Ca(2+) exchanger: a computer modeling

The aim of this work was to analyze the contribution of the Na+-Ca2+ exchanger in the generation of afterdepolarizations in a single cell by simulating the effects of free radicals in the context of ischemia-reperfusion, using a modified version of Luo and Rudy II action potential model (LRd model). To simulate the effects of ischemia three conditions were considered: hyperkalemia, acidosis and hypoxia. Simulations were run as long as steady state of all parameters of the model were reached, and then the availability of the Na+-Ca2+ exchanger current (INaCa) was varied. The generation of delayed after-depolarizations (DADs) depends on the extra cellular potassium concentration, [K+]o, and on the availability of INaCa. DADs observed during reperfusion period appeared when just a percent of INaCa was used.