Effect of calcium activated chloride current on characteristics of DAD

High intracellular calcium concentration causes a transient inward current (I/sub n/) that can provoke delayed after-depolarizations (DAD). I/sub n/ is comprised of sodium-calcium exchange current (I/sub NaCa/) and calcium-activated chloride current (I/sub ClCa/). We have developed a mathematical model of I/sub ClCa/ that was included into the atrium AP model by Linblad, Murphey, Clark and Giles (1996) (LMCG model). I/sub ClCa/ appears as an important component (30-40%) of I/sub n/. The plots of DAD amplitudes and DAD higher slope as a function of extracellular Ca/sup 2+/ concentration show an interval between 5 mM/l to 6 mM/l in which I/sub ClCa/ blockade could bring the DAD amplitude to a subthreshold level for triggered action potentials. Our results suggest that, at a high intracellular Ca/sup 2+/ concentration, that provokes DAD generating conditions, I/sub ClCa/ blockade could be potentially antiarrythmogenic.