CALCIUM CURRENTS IN DISEASED HUMAN CARDIAC-CELLS

Isolated atrial or ventricular human cardiomyocytes were dissociated from the heart of patients undergoing either open heart surgery (CS) or cardiac transplantation (CT). L-type Ca currents were recorded on cardiomyocytes from CS or CT by whole-cell voltage clamp technique. Although the electrophysiologic properties of L-type Ca current were similar in atrial and ventricular myocytes from CS and CT patients, cells from CT had larger capacitance and lower current density. Whereas isoprenaline (Iso) induced an increase in the Ca current amplitude both in atrial and ventricular cells, a serotoninergic agonist (5-HT4) enhanced Ca current only in atrial cells. Although the affinity for Iso and 5-hydroxytryptamine (5-HT) was not modified between CS and CT (K-0.5 = 0.1 mu M), the amplitude of the response to both Iso and 5-HT were altered in CT. Some electrophysiologic and pharmacological properties of Ca current are altered in cardiomyopathic human hearts. These alterations correspond to (a) a reduction in the number of functional L-type Ca channels, and (b) a decreased response to both beta-adrenergic and serotoninergic agonists, indicating that potentiation of Ca channel activity through the cyclic AMP pathway is altered.