Objective To study the adrenal function in rats with pulmonary acute lung injury (ALI) induced by Escherichia coli (0111B4) . Methods ALI rat model was induced by intratracheal injection of E.coli (3 ml/kg,0111B4,(4.4-5.6) x 10~(12) CFU/L).ALI rats were then randomly divided into three groups,and each group had 10 rats.Mechanical ventilation was applied at three time points,6 hours,24 hours,and 36 hours after injection At each time point 8 rats were used as control with saline administered intratracheally.The plasma ACTH and corticosterone levels were measured after stimulated by 100 μg porcine ACTH.Results Compared with control group,the model group had a higher level of plasma ACTH at each time point (P < 0.01).The plasma ACTH level reached the peak at 24 hours.The model group had a higher level of plasma corticosterone at 6 hours (P < 0.01) and 24 hours (P <0.05),but had a lower level of plasma corticosterone at 36 hours (P < 0.05).The plasma corticosterone level reached the peak at 6 hours in model group,which was higher than 24 hours (P < 0.05).After stimulated by ACTH,the increased levels of corticosterone were lower in model group than those in control group (6 hours,P < 0.05; 24 hours and 36 hours,P < 0.01).Conclusions Adrenal dysfunction may occur at early stage of ALI in rats.With the disease developed,adrenal response to ACTH decreased.Low dose corticotrophin-stimulated test could evaluate adrenal function in rats with pulmonary ALI induced by Escherichia coli (O111B4).