Strong Inhibition by 2-Chloroadenosine of the Aggregation of Blood Platelets by Adenosine Diphosphate

Abstract

WITH a turbidimetric method^1,2 it was shown that the aggregation of platelets that is brought about by adenosine diphosphate (ADP)³ is inhibited by adenosine monophosphate⁴ and, about ten times more strongly, by adenosine^2,5. The aggregating effect of ADP is very specific³. Our work^2,6 suggests that the molecular structure required to inhibit the effect is just as specific. Thus, we determined the inhibitory activities of 19 other substances, all related to adenosine, compared to the activity of adenosine itself. Only four of these substances had an inhibitory activity greater than 1 per cent of that of adenosine ; and the most potent of these four, with an activity of 5 per cent, was isoguanosine (2-oxy,6-amino purine riboside). Since the only difference between isoguanosine and adenosine is the substitution of a hydroxyl group for a hydrogen atom in position 2, another analogue of adenosine substituted only in that position, namely, 2-chloroadenosine, has now been compared with adenosine for inhibitory activity.