LY255283 is a specific antagonit of leukotriene B4 (LTB4) receptor. It inhibits the production of LTB(4) in human peripheral blood polymorphonuclear leukocytes (PMNL) and in monocytes activated by calcium ionophore A23187.

LTB4:100 nM (IC50, LTB4binds to guinea pig lung membranes)

All seven rats given only the vehicle died within 2 h of reperfusion, whereas rats treated with LY-255283 (3 or 10 mg/kg iv), a leukotriene B4 (LTB4) receptor antagonist given 10 min before reperfusion, exhibited significantly higher survival rates of 57% (4 out of 7) and 75% (6 out of 8), respectively, 2 h after reperfusion.?Rats given 1 mg/kg of LY-255283 showed no significant improvement in survival.?Splanchnic artery occlusion (SAO)-shock rats treated with LY-255283 (3 or 10 mg/kg) exhibited significantly attenuated accumulation of plasma free amino-nitrogenous compounds and of a myocardial depressant factor.?Treatment with LY-255283 (10 mg/kg) markedly (P less than 0.01) ameliorated the deficits of endothelium-dependent relaxation of isolated superior mesenteric artery (SMA) rings in untreated SAO-shock rats.?LY-255283 at 10 mg/kg significantly attenuated the increased myeloperoxidase activity in the intestinal tissue of SAO-shock rats[1].