LEUKOTRIENE-D(4) RECEPTOR BLOCKADE INHIBITS THE IMMEDIATE AND LATE BRONCHOCONSTRICTOR RESPONSES TO INHALED ANTIGEN IN PATIENTS WITH ASTHMA

We have tested the hypothesis that leukotriene D4 (LTD4) receptor activation is involved in the development of antigen-induced bronchoconstriction. In two studies, patients with asthma received infusions of placebo or MK-571, a potent and specific LTD4 receptor antagonist (450 mg or 37.5 mg total dose, respectively). Antigen was inhaled during test-drug administration, and FEV1 was measured for 10 hours after challenge. Urine samples were collected for measurement of LTE4; plasma samples were drawn repeatedly for assay of MK-571. MK-571 infusions inhibited both immediate (0 to 3 hours) and late (3 to 10 hours) asthmatic responses. For the high MK-571 dose, the extent of inhibition, as assessed by the area under the curve of FEV1 versus time was 88% (p = 0.01) and 63% (p = 0.01), for immediate and late responses, respectively. The low MK-571 dose also inhibited both responses but to a minor extent. Mean urinary LTE4 excretion was elevated after antigen challenge and was unaffected by administration of the LTD4 receptor antagonist. The present study demonstrates that MK-571 inhibits antigen-induced asthma in a dose-related fashion; it had no effect on antigen-induced increases in urinary LTE4 excretions. The results suggest that LTD4 receptor activation plays an important role in antigen-induced asthma.