Enhancement of Platelet Sensitivity to ADP-Aggregation by Isometric Exercise in Arteriosclerotic Patients and its Prevention

A new method for assessment of platelet sensitivity to ADP-aggregation was devised. Its reproducibility and the correlations between the values obtained by this method, the optical density (O. D.) method, and the screen filtration pressure (SFP) method were assessed. In summary, this method may be said to have three main points: 1. It can be performed without centrifugation, avoiding mechanical stress to platelets, using only 0.8 ml. of blood and inexpensive equipment. 2. It may reflect different aspects of platelet function from the O. D. method and the SFP method, despite the positve significant correlations between the values obtained by these three methods. 3. It was proved to be highly reproducible and is thought to be useful clinically. By using this method, the effect of sustained isometric exercise by handgripping on platelet aggregability was assessed in coronary sclerotic and cerebral arteriosclerotic patients on placebo and EG-626, a newly synthesized cyclic AMP phosphodiesterase inhibitor. On placebo, an enhancement platelet sensitivity was observed after isometric exercise in coronary and cerebral arteriosclerotic patients but not in healthy control subjects. The enhancement was prevented by pretreatment of EG-626, administered orally 1.5 hours prior to exercise.