Plasma adenosine levels and platelet activation in patients with atrial fibrillation

Platelet activation is observed in patients with atrial fibrillation (AF). P-selectin, which is expressed on platelet activation, plays an important r ole in the formation of thromboemobli, Because adenosine is known to attenu ate platelet activation, we evaluated adenosine levels and 2 indicators of platelet activation, i.e., expression of P-selectin on platelets and plasma levels of beta-thromboglobulin, in 28 patients with AF (20 men and 8 women , age range 64 +/- 2 years) with sex- and age-matched (+/- 2 years) subject s with sinus rhythm. The incidence of risk factors for stroke except for co ronary heart disease and in echocardiographic parameters did nat differ bet ween the 2 groups. Plasma adenosine levels were lower (p < 0.05) in patient s with AF than in controls (mean [interquartile range] 13.4 [19.3-9.3] vs 1 9.1 [30.8-11.9] nmol/L), The expression of P-selectin on platelets (6.8% [1 3.6-3.4] vs 4.0% [8.8-1.8]) and plasma levels of beta-thromboglobulin were higher (p < 0.05) in patients with AF. Flow cytometric analysis revealed th at an antagonist of adenosine receptors, 8-sulfophenylyheophylline, increas ed the expression of P-selectin on platelets in a dose-dependent manner in the in vitro study. These results suggest that decreased plasma levels of a denosine were associated with platelet activation in patients with AF. Subs titution of adenosine may provide a strategy for preventing platelet activa tion in these patients. (C) 1999 by Excerpta Medica, Inc.