Objective To investigate the effects of urotensinⅡ(UⅡ)receptor antagonist(URA)on UⅡ in plasma and bronchoalveolar lavage fluid(BALF)in rats with acute lung injury(ALI).Methods Twenty eight Sprague Dawley(SD)rats were randomly divided into four groups:saline control group(group A),the other three groups(group B,group C,group D).Rats were injected with oleic acid and URA to produce ALI models.Three hours after injection,arterial blood was drawn for blood gas analysis in all rats.Immediately after this,blood of heart was collected in group A and group B.Then blood of heart were collected after 12 hours in group C and after 24 hours in group D.Rats were killed when blood of heart was drawn.Bronchoalveolar lavage(BAL)with saline was performed in the right lung.BALF was centrifugated and the upper fluid was put to the EP tube.Plasma was separated from the blood of heart.Both plasma and BALF were kept at -80 ℃ to be determined.Results Compared with group A,arterial pressure of oxygen was significantly decreased in the group B,group C,group D(P