Spontaneous platelet aggregation primary thrombocythaemia

Abstract

Spontaneous platelet aggregation (SPA) in primary thrombocythaemia was examined using Bryston aggregometer by stirring at 37°C for 10min. of citrated original PRP (platelet count 87-296×10⁴/μl) or diluted PRP (3×10⁵/μl). SPA was found in 7 out of 8 patients in original PRP but in none in diluted PRP. The critical platelet levels for positive SPA were around 10⁷/μl. SPA occurred according to all or none law; as far as SPA occur, the maximum aggregation rate did not change whereas the lag time was increased with the decrease in platelet concentration. No correlation was found between SPA and clinical symptoms or platelet lipoxygenase or cyclo-oxygenase levels. Among EDTA-2K, citrate and heparin, EDTA was the strongest to inhibit SPA. SPA was inhibited with EDTA over 0.075% at final concentration. SPA was also inhibited by dipyridamole (5×10^-5-5×10^-1mg/ml at f. c.), VCR (10^-4mg/ml) and adenosine (10^-5-5×10^-5M). Oral administration of aspirin (10mg/kg) inhibited SPA for 24 hours in all cases and did not 96 hours after the administration in all cases. This result was almost coincident with that of suppresion of aggregation induced by collagen (1μg/ml). The surface morphology of SPA was almost equal to that of irreversible aggregates with release reaction by collagen or ADP. Clinically the administration of small dose of aspirin once a day or two days may be sufficient to prevent SPA and aggregation by collagen.