RELATIONS OF PLATELET CA2-ARTERY( HANDLING AND MEMBRANE MICROVISCOSITY TO VASCULAR TONE AND RESTENOSIS AFTER ANGIOPLASTY IN HUMAN CORONARY)

This study was designed to assess whether platelet Ca2+ handling or me mbrane microviscosity could be considered as indexes of vascular tone, or could help to predict an increased risk of restenosis after corona ry angioplasty. Vascular tone was quantified in 21 patients with stabl e angina by the vasodilator response to sin-1 intracoronary injection in the reference coronary segment and by the importance of the acute r ecoil after angioplasty in the narrowed segment. The degree of resteno sis was quantified by coronary angiography 6 months later. Individual values of relative sin-1-induced changes in the reference coronary dia meter were positively correlated with cytosolic Ca2+ concentration in unstimulated platelets, irrespective of the extracellular Ca2+ concent ration (p <0.01). This relationship was also observed with the thrombi n-evoked Ca2+ changes, measured in the absence of a Ca2+ influx (p = 0 .01) No relationship was found between sin-1-induced coronary changes and membrane microviscosity evaluated by TMA-DPH and DPH anisotropies or platelet volume, or between degree of acute recoil and platelet cha racteristics. In conclusion, platelet Ca2+ reflects the vasodilating e fficacy in response to sin-1, but cannot help to predict restenosis af ter coronary angioplasty.