Thrombocytosis and platelet aggregates in the circulation of adjuvant arthritic rats.

A marked increase in platelet count was observed in adjuvant-induced polyarthritic rats. Elevation of platelet count was still significant 3 months after onset of disease. Increased number and larger size of platelets reflect an increase in the rate of platelet production. By means of the platelet-count ratio technique, circulating platelet aggregates were demonstrated in rats with severe arthritis. Aspirin treatment prevented thrombocytosis and formation of platelet aggregates.