Changes of endogenous glutamate release in lungs of newborn rats with hyperoxia-induced lung injury

AIM To demonstrate the role of intrinsic glutamate(Glu) in hyperoxia-induced lung injury.METHODS SD newborn rats,in 12 h after birth,were randomly divided into 2 groups:air control and hyperoxia(95% oxygen) groups.After 1,3 and 7 d of continuous exposure to high concentration oxygen,the lungs of 5 rats in each group were removed.Then the wet-to-dry weight ratio(W/D) was measured and histopathological changes were observed with HE staining.The bronchoalveolar lavage fluid(BALF) of other rats in each groups was prepared and the leucocyte numbers,total protein(TP) concentrations and lactate dehydrogenase(LDH) activity in BALF was determined with hemocytometer,Lowry method and automatic biochemical analyzer,respectively.In addition,the level of Glu in BALF was determined by using high performance liquid chromatograph.RESULTS There was no difference in W/D between the air control and hyperoxia groups 1 d after hyperoxia exposure.After 3 and 7 d,W/D in hyperoxia groups were much higher than that of the air control group.HE staining showed that a few inflammatory cells appeared in some alveolar space in the hyperoxia group on 3 d.On 7 d,leukopedesis and red blood cells increased in the alveolar space,and there were fewer alveolai compared with control group.On 1 d,LDH activity in hyperoxia group was significantly higher than that in control group.The TP contents and leucocyte count had no obvious changes between the 2 groups.On 3 and 7 d,LDH activity,TP content and leucocyte count in hyperoxia groups were much higher than that of control group.In addition,the glutamate level in BALF on 1 and 3 d of hyperoxia exposure was significantly higher than that in control group.CONCLUSION Hyperoxia can induce acute lung injury and intrinsic Glu release in lungs of newborn rats,which show that Glu may play an important role in hyperoxia-induced lung injury.