Platelet adhesion and aggregation on polyethylene: effect of exhaustive exercise.

The aim of the present study was to evaluate the effect of an exhaustive exercise on platelet adhesion and aggregation on polyethylene (PE) in relation to changes in plasma cortisol concentration in order to ascertain the effect of physical stress response in the blood-contacting properties of polymeric materials. Twelve healthy sedentary subjects, six males and six females, were studied. Each subject performed an exercise test on a bicycle ergometer at intensity corresponding to 70% VO2 max until exhaustion. One month after the exercise session, each subject participated in a control rest session. In both sessions, blood samples were drawn every 5 min for cortisol, lactate, hemoglobin, and hematocrit determinations and every 15 min for evaluation of platelet adhesion and aggregation. Individual comparisons between the rest and exercise cortisol patterns identified three categories of cortisol responders to exercise: positive responders (C +, showing higher concentrations during exercise than during rest), negative responders (C -, showing lower concentrations during exercise than during rest), and nonresponders (NR, showing similar concentrations during exercise and rest). The results revealed that C + had lower platelet adhesion and aggregation scores during exercise than during rest; moreover C - had higher scores than C + and NR during exercise. The results obtained demonstrated no effects of sex or exercise on either cortisol plasma levels or platelet adhesion and aggregation on PE surface. With regard to cardiovascular risk, the results suggest that exercise favorably affects platelet functions when mechanisms of metabolic adaptation to prolonged muscular work, expressed by a cortisol increase, are activated during exercise.