Effect of leukotriene receptor antagonists on lung fibrosis in rats.

To compare the effects of montelukast, prednisone and the combination of both drugs in a rat model of bleomycin-induced lung fibrosis. Rats, injected intravenously with bleomycin daily for five consecutive days, were treated with either montelukast, prednisone or a combination of both drugs orally daily for 35 days starting 14 days after the commencement of the first dose of bleomycin. Montelukast-treated rats showed reduction in collagen deposition by 29% and significant reduction in lung hydroxyproline content by 32%. Prednisone produced nonsignificant difference in collagen deposition and in lung hydroxyproline content compared with the bleomycin group. There was also a significant reduction in collagen deposition and hydroxyproline content in montelukast and prednisone treated rats by 15 and 17%, respectively, compared with bleomycin group. A significant reduction occurred in the mean area percentage of myofibroblast α smooth muscle actin in montelukast and montelukast and prednisone-treated groups by 41 and 37%, respectively, with nonsignificant difference in prednisone-treated rats as compared with the bleomycin group. Montelukast may be therapeutically effective for inhibiting further progression of lung fibrosis through inhibition of α-SMA positive myofibroblasts.