Effect of plasma calcium concentration on aggregation of platelets

Objective To study the effect of plasma calcium concentration on aggregation of platelets. Methods Different amounts of CaCl2 were added into venous blood samples taken from healthy volunteers（n=42）.Aggregation of platelets was detected by plasma turbidimetry. Results when the plasma calcium concentration was 2.11-0.12mmol/L,the aggregation rate of platelets induced by adenosine diphosphate（ADP） and arachidonic acid（AA） was（75.9±10.4）%-（51.8±9.6）% and（83.7±13.9）%-（64.4±12.2）%,respectively（P＜0.01）,and then decreased with the decreasing concentration of Ca2+.When the plasma calcium concentration was 2.11-33.66mmol/ L,the aggregation rate of platelets induced by ADP and AA was（75.9±10.4）%-（94.7±4.8）% and（83.7±13.9）%-（93.2±5.5）%,respectively（P＜0.01）,and then increased with the increasing concentration of Ca2+.When the plasma calcium concentration was 39.00 mmol/ L,the aggregation rate of platelets induced by ADP and AA was 9.1%±5.3% and 11.1%±4.5%,respectively（P＜0.01）. Conclusion Plasma calcium concentration has a significant effect on aggregation of platelets.When the physiological concentration of Ca2+ is lower than 2.1mmol/L,the aggregation rate of platelets decreases with the decreasing concentration of Ca2+.When the physiological concentration of Ca2+ is higher than 2.1mmol/L,the aggregation rate of platelets increases with the increasing concentration of Ca2+.The aggregation of platelets is inhibited when the plasma calcium concentration is≥39.0 mmol/L.