Effects of different anticoagulants on human platelet size distribution and serotonin (5-HT) induced shape change and uptake kinetics

Abstract

The effect of collecting blood with disodium ethylene diamine tetra-acetate (EDTA), citrate (NAC) or acid sodium citrate-dextrose (ACD) as anticoagulants on platelet count and size distribution was investigated. No difference between the three preparations regarding platelet count was found in whole blood. Preparation of platelet-rich plasma (PRP) significantly reduced the platelet count in NAC-PRP (p<0.01) to a value of 288 × 10 9/1 compared to those of 365 × 10 9/1 and 368 × 10 9/1 in EDTA and ACD blood respectively. A significant shift in the platelet size in EDTA-PRP towards larger cell volumes was observed. There were no differences in the size distribution patterr between NAC-PRP and ACD-PRP in spite of the differences in platelet count. Platelet 5-HT uptake kinetics in EDTA-PRP showed a 50 per cent reduction in both K m and V max compared to that in ACD-PRP. The study shows that the receptor mediating 5-HT induced shape change has a direct opposite pH dependence than that of the 5-HT carrier. Interference of receptor-mediated responses in 5-HT uptake studies in human platelets is clearly minimized at a lowered pH. The finding is probably of importance in disorders associated with platelet hyperaggregability.