CARDIAC-HYPERTROPHY DETERMINES DIGITALIS ACTION ON INTRACELLULAR CA2+IN HUMAN MYOCARDIUM

Ventricular hypertrophy alters transporters associated with digitalis action, but the outcome of digitalis treatment on intracellular cation s in the hypertrophied human myocardium remains unknown. Using double- barreled Ca2+-selective microelectrodes, we simultaneously measured Ca 2+ activity and membrane potential in myocardial samples from patients without and with ventricular hypertrophy, prior to and following expo sure to strophanthidin, a prototype digitalis. We found that ventricul ar hypertrophy is associated with greater strophanthidin-induced incre ase in diastolic Ca2+ levels compared to that observed in the absence of hypertrophy. Furthermore, in hypertrophied myocardium the magnitude of the increase in Ca2+ induced by strophanthidin was inversely relat ed to increase in myocardial mass. Thus, the extent of ventricular hyp ertrophy determines digitalis action on intracellular Ca2+ within the human myocardium. (C) 1997 Elsevier Science B.V.