[Arachidonic acid metabolites in exercise-induced asthma]

Plasma levels of arachidonic acid metabolites, such as thromboxane A2 (TXA2), prostacyclin (PGI2) and leukotrienes (LTS) were measured in patients with exercise-induced asthma (EIA). Asthmatic patients were exercised by treadmill. Before, immediately after and at 5, 15 and 30 minutes after exercise, pulmonary function tests were performed and peripheral venous blood was collected at the indicated times. Plasma TXB2 levels rose after exercise, and this tendency was stronger in EIA negative patients than in EIA positive patients. Plasma 6-keto-PGF1 alpha levels rose slightly after exercise in both EIA positive and negative patients. Plasma LTC4 levels were almost unchanged after exercise in EIA positive patients. Plasma LTC4 levels rose after exercise in EIA negative patients, though the value was always higher in EIA positive patients than in EIA negative patients. Plasma LTB4 levels in both EIA positive and negative patients increased slightly till 5 minutes after exercise, then decreased, and then tended to rise again. Plasma LTB4 levels were higher in EIA positive patients than in EIA negative patients at all times. The ratio of TXB2 to 6-keto-PGF1 alpha after exercise rose more remarkably in EIA negative patients than in EIA positive patients. From these results, we suspected that the metabolites of arachidonic acid may contribute less to chemical mediators of EIA, but the arachidonic acid products of EIA positive patients activated rather towards lipoxygenase cascade than EIA negative patients.