RELEASE OF ADENOSINE-TRIPHOSPHATE BY ADENOSINE-DIPHOSPHATE IN WHOLE-BLOOD AND IN ERYTHROCYTE SUSPENSIONS

In whole blood samples from thrombocytopenic patients, large amounts o f ATP were released by ADP, exceeding the level obtained with samples from normal persons by far, Because we suspected that the high potenti al of ATP in erythrocytes would be the main source for this phenomenon , the release of ATP by ADP was measured in whole blood samples from n ormal, thrombocytopenic, and leukocytopenic persons and in suspensions of washed erythrocytes. The release was recorded by a Whole Blood Lum i-Aggregometer type 500 VS (Chrono-Log Corporation, Havertown, PA) usi ng the luciferin-luciferase system, Not only in samples from thrombocy topenic persons but also with normal platelet count, increasing amount s of ATP were released with increasing ADP concentrations, finally exc eeding the ATP releasable from thrombocytes by thrombin, The amounts o f ADP required to match the ATP release of thrombin were closely corre lated with the platelet counts in the samples, With lower platelet cou nts, the release mechanism from erythrocytes could be stimulated more easily by low concentrations of ADP, The binding of ADP to platelets o ccurred with ostensibly higher affinity, The phenomenon of overshootin g ATP release was also observed in samples from extremely leukocytopen ic patients, A very large release of ATP was also achieved in suspensi ons of washed erythrocytes, In this way our hypothesis of ATP release from erythrocytes by ADP was confirmed again, The mechanism of the rel ease from erythrocytes remains unclear, We speculate that its purpose is to regulate extracellular nucleotides in the circulating blood. (C) 1997 Wiley-Liss, Inc.