BASAL AND THROMBIN-STIMULATED PLATELET CELL CALCIUM

To study platelet cell calcium in dogs, we measured the fura-2-determined calcium concentration (Ca-i) in platelets derived from blood drawn through indwelling arterial catheters in four dogs. Platelet samples were obtained 3 days a week for 39 days. Canine platelet Ca-i averages 40.5 +/- 1.7 nmol/L when corrected for extracellular fura-2 dye (n = 46); this mean is significantly smaller than the value obtained without such a correction (50.2 +/- 2.0 nmol/L, P<.05). The amplitude of thrombin-induced Ca2+ transients is proportional to basal Ca-i increasing 4.9 +/- 0.9 nmol/L peak Ca2+ per nmol/L increase in baseline Ca2+.