DYNAMICS OF THE CALCIUM SUBSYSTEM IN CARDIAC PURKINJE-FIBERS

A minimal model of the dynamics of internal calcium concentration of t he mammalian cardiac Purkinje fiber is examined in order to identify t he cause of certain arrhythmias of the heart. The effect of inhibition of the sodium/potassium pump is modeled by an elevated value of inter nal sodium concentration. Effects of pump inhibition are examined at d ifferent clamp voltages. Such conditions mimic those which have been e xamined experimentally and which are known to cause oscillatory calciu m release [W.J. Lederer, PhD thesis, Yale University, New Haven, CT (1 976), 168 pp.; R.S. Kass, W.J. Lederer, R.W. Tsien and R. Weingart, J. Physiol. (London) 281 (1978) 187-208). System dynamics are investigat ed using numerical continuation methods. Results of these analyses pre dict the existence of stable periodic oscillations of internal calcium over a range of voltage-clamp values. The emergence of these oscillat ions depends on the intracellular sodium concentration.