Adenosine metabolism in dog whole blood: Effects of dipyridamole

Abstract

The effects of dipyridamole on the metabolism of adenosine added to dog whole blood were studied in vitro at 37°C. The half-lives for 8.8μM and 100μM adenosine were 3.42 and 6.89 min, respectively. Dipyridamole, in concentrations of 10 −7 to 10 −4M increased the half-life of 8.8μM adenosine 2 to 5-fold. The disappearance rate of adenosine in the presence of 10 −4 dipyridamole was similar to the disappearance rate of adenosine in plasma. Inosine formation was enhanced by dipyridamole. Control blood samples not receiving exogenous adenosine showed an increase in endogenous adenosine and inosine during 30 min of incubation. Endogenous production of nucleosides was unaffected by dipyridamole. Analysis showed that endogenous adenosine approached a steady-state concentration of 1μM. The results indicate that the half-life for adenosine in dog whole blood is significantly greater than previously reported and that dipyridamole is effective in inhibiting adenosine disappearance in concentrations as low as 10 −7M. The implications of endogenous production of adenosine are discussed.