Effect of prolonged exercise on neutrophil myeloperoxidase secretion.

This study was designed to compare the effects of three prolonged exercises on plasma myeloperoxidase concentrations, used as marker of neutrophil degranulation. Seven healthy subjects underwent three effort trials (45% VO2max during 4 h, 60% VO2max during 3 h, 75% VO2max during 2 h) at one-month intervals. Blood samples were collected before, during and after exercise. Myeloperoxidase levels were measured by radioimmunoassay. We observed a significant increase in myeloperoxidase concentration (+85%) at the end of our three prolonged exercises (p < 0.05). This myeloperoxidase increase was not correlated with the modification of neutrophil count, suggesting that neutrophil degranulation is independent of their mobilisation.