Platelet adhesion in hypertension: application of a novel assay of platelet adhesion

BACKGROUND: The increased risk of thromboembolism in hypertension may be related to a prothrombotic or hypercoagulable state, with abnormalities in haemostasis and platelet function. OBJECTIVE: To investigate the role of platelets in the pathogenesis of thrombosis in hypertension, we applied a novel new assay to detect and quantify the degree of platelet adhesion to a defined coagulation molecule. PATIENTS AND METHODS: Platelet-rich plasma (PRP) and citrated plasma (CP) were obtained from 50 patients with hypertension (25 treated, and 25 untreated) and 30 healthy controls. A suspension of 2 x 10(7) platelets were incubated for one hour in microtitre plates pre-coated with 5mg/mL fibrinogen. The supernatant was carefully aspirated, lysed with 5% tween and stored at -70 degrees C as supernatant platelet lysate (SPL). The wells were carefully washed with saline and bound platelets lysed as before, and stored at -70 degrees C as bound-platelet lysate (BPL). Soluble P-selectin (sP-sel) was determined in CP, SPL and BPL by enzyme-linked immunosorbent assay (ELISA). RESULTS: Patients with hypertension (both treated and previously untreated) had increased platelet adhesion, as determined by increased lysate sP-sel (P=0.002) in BPL, with no change in SPL (P=0.5) compared to healthy controls. There was no significant difference between treated and previously untreated hypertensives. CONCLUSION: Platelets from patients with hypertension display increased adhesion to an important coagulation factor (fibrinogen). This may, in part, account for the increased risk of thrombosis seen in these patients.