CHARACTERISTICS OF CALCIUM-CURRENT IN ISOLATED HUMAN VENTRICULAR MYOCYTES FROM PATIENTS WITH TERMINAL HEART-FAILURE

The Ca2+-current plays a prominent role in triggering excitation-contraction coupling in the mammalian heart. It is also a target of clinically important drugs such as catecholamines or Ca2+-channel blockers. Unitl now studies of Ca2+-channels in human ventricular myocardium have been hampered by the fact that adequate voltage control cannot be obtained in multicellular preparations. To characterize the properties of human myocardial Ca2+-currents, ventricular myocytes were isolated from explanted hearts of patients with end-stage heart failure undergoing cardiac transplantation. The current-voltage relation and voltage-dependent inactivation of L-type currents were similar to those in non-diseased guinea-pig myocardium. Currents could be stimulated with isoprenaline in a dose-dependent manner. When cells were superfused with a Na+-free solution in the presence of Tetrodotoxin, Cs+ and Tetraethylammonium to block interfering Na+ and K+-currents, depolarization from a holding potential of -90 mV to -80 - -50 mV did not elicit any time-dependent inward-current. Changing the holding potential from -90 to -45 mV did not alter the current-voltage relation. We conclude that T-type Ca2+-currents do not seem to make a detectable contribution to the transmembrane Ca2+-influx and that L-type currents in human ventricular myocytes of patients with severe heart failure have characteristics that are similar to those in other mammalian species. © 1991.