INCREASED CYTOSOLIC-FREE MG2+ AND CA2+ IN PLATELETS OF PATIENTS WITH VASOSPASTIC ANGINA

This study was designed to test the hypothesis that the cellular metab olism of Ca2+ and Mg2+, which is important in platelet function, is ab normal in the platelets of patients with vasospastic angina. Cytosolic free Mg2+ concentration ([Mg2+](i)) and Ca2+ handling were determined in the platelets of 24 patients with vasospastic angina and 24 contro l subjects by use of mag-fura 2 and fura 2. Platelet aggregation was a lso examined. Basal [Mg2+](i) and cytosolic free Ca2+ concentration ([ Ca2+](i)) in platelets were significantly higher in patients with vaso spastic angina than in control subjects. The amplitude of the [Ca2+](i ) transient induced by thrombin (0.03-1.0 U/ml) was significantly incr eased in the presence, but not in the absence, of extracellular Ca2+ i n patients with vasospastic angina, as compared with controls. Therefo re, the influx of Ca2+ across the plasma membrane may be accelerated i n vasospastic angina. Thrombin (0.1-1.0 U/ml)-induced maximum aggregat ion response was significantly greater in patients with vasospastic an gina than in controls. Results suggest that increased [Mg2+](i) and al tered Ca2+-handling by platelets may be associated with coronary vasos pasm.