Expression Of Insulin-Like Growth Factor-1 In Brain Tissue Of Neonatal Rats With Hyperbilirubinemia

Objective:To observe the expression of insulin-like growth factor-1(IGF-1)in the brain tissue of neonatal SD rats with hyperbilirubinemia and its effect on apoptosis,and to explore the role of IGF-1 in the brain injury of hyperbilirubinemia and its possible mechanism to provide some basic experimental research for the clinical diagnosis and treatment of bilirubin encephalopathy.Methods:A total of 120 neonatal SD rats aged 7 days were selected and were randomly divided into normal saline control group(group A,n=40)and hyperbilirubinemia groups(group B,n=40 and group C,n=40).Rats in group A were given intraabdominal injection of normal saline 100ug/g,rats in group B and group C were given intraperitoneal injection of bilirubin solution 100ug/g,150ug/g respectively.Each group was divided into five subgroups according to the time points of the rats being killed(6h,12 h,24h,48 h and 72h),8rats in each subgroup.Abnormal neural behaviors of newborn rats were observed.Hematoxylin eosin(HE)staining was used to observe pathological changes of brain tissue.Tunel method was used to measured the number of apoptosis of brain tissue.Immunohistochemistry was used to analyze the expression of IGF-1 of brain tissue.Then the results of the experiment were recorded.All the relevant data were calculated and the statistical analysis was carried out.And the conclusions have been drew finally.Results:(1)Observation of rats behavior : After set up the model,in group A,there was no abnormal neurobehavioral performance.In group B,14 rats began to take on abnormal behavior such as toss,tremor and depression at 12 hours.In group C rats began to have abnormal behavior at 8 hours,and 30 rats had abnormal neurobehavioral behavior at 36 hours.And the performance was more obvious than that in group B.(2)HE staining:In group A,no bilirubin deposition in the hippocampal region.The cells were arranged neatly.The morphology was normal,and the nucleolus was clear.In group B,bilirubin deposited in The hippocampal region.The number of cells was reduced.The cells were swollen and deformed.And some of the nuclei disappeared.In group C,a large amount of bilirubin deposited in the hippocampal region.The cell structure was disorganized and the nucleus retraction,fragmentation and dissolution were basically conformed to the morphological changes of cell apoptosis.(3)Apoptosis and expression of IGF-1:In group A,there was no or only small amount of apoptosis and expression of IGF-1 in the hippocampus of neonatal rats.In group B and group C,the apoptosis and IGF-1 of the neonatal rats were expressed at different times.And the expression peaked at 48 hours and was constant high for 72 hours.There was statistically significant difference between the two group(P<0.05).Compared with group A,group B and group C at the same time point,the expression of apoptosis and IGF-1 were C>B>A.There were statistically significant differences among them(P<0.05).The expression of IGF-1 was positively correlated with the rate of apoptosis the hippocampus of brain tissue(r=0.992 P<0.01).Conclusion:(1)IGF-1 participates in the pathophysiological process of the apoptosis of the brain tissue of hyperbilirubinemia of neonatal SD rats.(2)When hyperbilirubinemia occurs,the expression of IGF-1 increased with the increase of bilirubin solution entering into brain tissue.It may play an important neuroprotective role in brain injury of hyperbilirubinemia.