ACUTE EXERCISE INCREASES PLATELET RESPONSE TO ADP AND COLLAGEN IN RATS

Abstract

Acute exercise increases the risk of vascular thrombotic events. Interactions among platelets and the vessel wall involve in the progression of these events. Therefore exercise-induced alterations in platelets may play a role in progression of vascular thrombosis. PURPOSE To evaluate the effect of acute exercise on platelet aggregation and degranulation. METHODS 14-16 weeks old male Spraque-Dawley rats were randomly assigned to either a control group (n = 14) or to an exercise group (n = 18). The exercise group ran on a motorized treadmill for 60 minutes at approximately 65% of maximal oxygen uptake after a period of habituation. The animals were anesthetized and blood samples were taken from the abdominal aorta. ADP and collagen-induced platelet aggregation was determined by impedance technique. Platelet degranulation was evaluated by measurement of ATP release using lumiaggregometer. Mann-Whitney U test was used to compare the parameters of the control and the exercise grops. A probability level of p £ 0.05 was considered significant. RESULTS Maximal rate (MR) of ADP-induced platelet aggregation was 1.86 ± 0.94 ohm/min in controls and was 2.39 ± 1.09 ohm/min in the exercise group. MR of collagen-induced aggregation was 2.07 ± 1.33 ohm/min in the control group and was 2.33 ± 0.59 in the exercise group. Collagen-induced platelet aggregation of the exercise group were higher than of the control group (p < 0.05). ADP-induced platelet ATP release was 1.91 ± 0.81 nM in controls and it was 2.54 ± 0.45 nM in the exercise group. Collagen-induced ATP release of the platelets in the control group was 0.76 ± 0.67nM and it was 1.55 ± 0.48 in the exercise group. Both ADP and collagen-induced platelet ATP release were higher in exercise group than the control group (p < 0.05). CONCLUSION These results show that acute exercise at 65% maximal oxygen uptake results in platelet hyperreactivity. Exercise-induced platelet aggregation and degranulation may contribute to the increase in the risk of vascular thrombotic events during physical exercise.