EFFECTS OF ADENOSINE ON EX-VIVO FILTRAGOMETRY PLATELET-AGGREGATION INRELATION TO PLASMA-LEVELS

The aim of the present study was to investigate the concentration effe ct of adenosine on unstimulated platelet aggregation in humans. Adenos ine infusion was given intravenously to 12 volunteers in the antecubit al vein with infusion rates increasing from 20 to 100 mu g kg(-1) min( -1). Filtragometry measurements were obtained from the contralateral a ntecubital vein before and during 100 mu g kg(-1) min(-1) or during ma ximal tolerable infusion rate. In another set of experiments with 10 v olunteers, basal filtragometry measurements were obtained before and a fter infusion of various concentrations of adenosine into the filtrago meter test unit. With intravenous infusion aggregation time tended to increase from 333+/-42 to 418+/-8 s (mean+/-SEM) and increased the ven ous plasma adenosine concentration from 0.42+/-0.09 mu M to 1.52+/-0.3 8 mu M. Adenosine infusion into the filtragometer tubing system dose-d ependently inhibited aggregation (P < 0.05). Adenosine was rapidly eli minated with a half-life of adenosine in the filtragometry tubing syst em calculated to be about 6 s. These data extend our knowledge from an in vitro to an ex vivo situation that adenosine dose dependently has a platelet antiaggregatory effect.