The effect of cytotoxic lymphocytes on contraction, action potential and calcium handling in cultured myocardial cells

Cytotoxic T lymphocytes are important in the pathogenesis of several disease states, yet the pathophysiology of the lymphocyte-myocyte interaction is not well known. We have developed in vitro vital and autoimmune models to study the physiological phenomena associated with this interaction. To produce these models, lymphocytes were obtained from adult rats injected either with mengo virus or autologous cardiac myocytes. Cardiac myocytes from neonatal rats were then exposed to these lymphocytes. In both models, reversible physiologic changes in myocytes preceded irreversible cell damage. The physiologic changes included reduced amplitude of myocyte contraction, impairment of relaxation and prolongation of the duration of contraction and action potential. In addition, oscillations were noted in the plateau phase of the action potentials. These physiologic changes were accompanied by an early elevation in the cytosolic free calcium concentration, a late elevation in the total exchangeable calcium pool, and attenuation of the [Ca²⁺](i) transient signals. Verapamil inhibited the late elevation in the total exchangeable calcium pool, but failed to inhibit the early elevation in the cytosolic free calcium concentration. These phenomena may explain transient cardiac functional abnormalities that may appear during myocarditis prior to cell destruction.