The contractile activities of lipoxin A4 and lipoxin B4 for guinea‐pig airway tissues

Abstract

1 The isometric contractile activities of lipoxin A₄ (LxA₄) and lipoxin B₄ (LxB₄) were evaluated on guinea-pig lung tissue over the concentration range, 10⁻⁸ to 10⁻⁵ m. 2 LxA₄ contracted guinea-pig lung parenchymal strips; the concentration eliciting 50% maximum histamine response was 3 × 10⁻⁶ m. LxA₄ did not contract tracheal spirals. 3 The LxA₄ dose-response curve was parallel to that of leukotriene D₄ (LTD₄) with LxA₄ being approximately 10,000 fold less potent than LTD₄. 4 The time course of the contraction elicited by LxA₄ was similar to that of LTD₄ and it was slow in onset and did not plateau for 20 min. 5 Pre-incubation of parenchymal strips with leukotriene receptor antagonists at a concentration of 1 × 10⁻⁶ m to 3 × 10⁻⁵ m FPL 55712 or 3 × 10⁻⁵ m L 649923 inhibited LxA₄ activity. 6 Pre-incubation of tissues with 1 × 10⁻⁵ m L 651392, a 5-lipoxygenase inhibitor, or 1 × 10⁻⁵ m indomethacin, a cyclo-oxygenase inhibitor, did not affect the contractile activity of LxA₄. 7 LxB₄ did not constrict parenchymal strips or tracheal spirals.