ABSTRACT
<p><b>OBJECTIVE</b>To investigate the mechanism of hepatocytic insulin signal transduction defects in severely scalded rats, so as to clarify the molecular basis of postburn insulin resistance.</p><p><b>METHODS</b>Wistar rats inflicted by 30% III degree scalding on the back were employed as the model. The rat hepatocytic insulin receptor was partially purified by wheat-germ agglutinin (WGA)-sepharose 4B affinity chromatography. The change of receptor tyrosine protein kinase (TPK) activity, the receptor beta-subunit autophosphorylation and the hepatocytic insulin receptor binding behavior of scalded rats during early stage of scalding were observed by means of insulin receptor binding test, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) autoradiography of phosphorylation of insulin receptor and phosphorylation of exogenous substrate.</p><p><b>RESULTS</b>There exhibited no evident changes of hepatocytic insulin receptor maximal binding capacity and affinity at 3 postburn days (PBDs) in scalded rats. The autophosphorylation capacity of the receptor beta-subunit decreased significantly. And the receptor TPK activity decreased obviously and its reaction to insulin stimulation decreased markedly.</p><p><b>CONCLUSION</b>The defects of the insulin receptor signal transduction in hepatocyte leading to the post-receptor defects of insulin biological effects might be molecular mechanism of postburn insulin resistance.</p>
Subject(s)
Animals , Rats , Burns , Metabolism , Pathology , Disease Models, Animal , Hepatocytes , Metabolism , Insulin , Physiology , Insulin Resistance , Physiology , Phosphorylation , Rats, Wistar , Receptor, Insulin , Metabolism , Signal Transduction , PhysiologyABSTRACT
Objective To observe the pathological changes of liver cells in the early periods of burn injury combined with endotoxemia and to explore its mechanisms preliminarily. Methods Rats were inflicted with 20% TBSA Ⅲ degree burn combined with intraperitoneal injection of lipopolysaccharide (burn injury combined with endotoxemia, combined group) or simply burned or simply injected. Each group included 25 rats, with 5 rats left for control. Rats in the former 3 groups were sacrificed and sampled at 1, 3, 6, 12 and 24 h after injury, 5 rats for each time point. The results were observed by HE staining, TUNEL and DNA gel electrophoresis, and the concentrations of plasma MDA and the activity of plasma SOD were assessed and analyzed. Results Apoptosis of liver cells was found in each of the 3 groups but its regularity was different from one another. Much more apoptotic cells in the combined group were found than the other 2 groups and apoptosis happened earlier with its maximum at 6 h postinjury and declined thereafter. Much less apoptotic cells were found in the simply burned group and reached the maximum at 12 h postburn. There were only a few apoptotic cells at 6 h postinjection in the simply injected group in which there were the fewest apoptotic cells in the three groups. The concentration of plasma MDA and the activity of SOD always moved in the opposite way at the same time. In the combined group, the maximum of MDA concentration and the minimum of SOD activity happened at the same time point, which was just before the one of the maximum of liver cell apoptosis. Conclusion During the early period of burn injury combined with endotoxemia, rat liver cells die mainly in the apoptotic way, with lots of apoptotic cells at 6 h and 12 h postinjury, combined with necrosis at 24 h. Lipid peroxidation may partly account for the apoptosis of liver cells.
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Objective To explore the mechanism of effects o f endotoxin (LPS) on apoptosis of pancreatic islet cells in rat.Metho ds After the model of endotoxemia was established in rat with intrap eritoneal injection of LPS (2mg/kg),the changes of nitric oxide (NO) level in se rum and pancreas were dynamically determined.The expression of inducible nitric oxide synthase (iNOS) was also observed by situ hybridization in the islet,Moreo ver,DNA damage in islet cells by the external donor of NO (sodium nitroprussid e) and LPS in vitro with single cell gel electrophoresis and agarose gel electro phresis of DNA were also evaluated.Results NO level in se rum was significantly increased at the 6th,and persisted to the 3rd day after in jection of LPS,the NO in pancreas was also elevated,but recovered to the normal at 24h. The expression of iNOS in pancreatic islet also began to enhance at the 6th and significantly enhanced at the 12th after endotoxemia.In vitro experiment sho wed that exogenous NO markedly caused the damage of DNA in islet cells,but LPS d i d not exert the same effects.Conclusion The mechanism of the effcts of endotoxin on apoptosis of islet cells might stimulate the expressi on of iNOS in inflammatory or non-inflammatory cells that generates the NO indu cing the DNA damage of islet cells.
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This article is to introduce our method to determine the erythrocytic insulin receptors of four different species of animals including human being. A small amount of blood with Normal buffer as incubation medium was put at 4℃ over night and then the binding rate of the erythrocytes with 125I-insulin was tested. The highest binding rates (B/T%)of the erythrocytes from human beings, rabbits, dogs and rats were within the range from 10%to15% and the average of nonspecific binding rates was 3.5%. In different animals, the number of erythrocytic insulin receptors was also different, which was the largest in dogs, then in rabbits and in rats, and the smallest in human beings. The competition inhibition curve of the binding of the erythrocytic insulin receptors with 125I-insulin accorded with the nonlinear Scatchard plots and was similar to the results reported by other authors.Our experiment showed that good results could also be obtained if Normal Buffer was used ot subsitute Buffer G as the incubation medium. Moreover, the degradation rate of insulin-receptor Complex could be reduced when the test was carried out at 4℃,so this method would be useful to assay the erythrocytic insulin receptors in clinical practice.
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Objective To investigate the relationship of hyperglycemia to trauma score,infection,MODS and survival time of the dead patients caused by trauma.Methods A total of 455 cases of dead trauma patients selected randomly from our hospital,were divided into two groups with normal blood glucose(n=57) or hyperglycemia(n=298).The RTC,GCS and the cases of infection and MODS as well as the survival time of two groups were recorded,and the coefficients of relationship between the blood glucose and the indexes of MODS in the dead trauma patients were calculated.Results The levels of RTC,GCS in the group with hyperglycemia were higher than that with normal blood glucose(P
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The possible mechanism of insulin resistance of the adipose tissue after burn injury was studied.The binding activity of the insulin receptors,the insulin effects on insulin-sensitive phosphodiesterase(PDE)and the level of free fatty acid(FFA)and cAMP were observed for 4 d in the adipose tissue of the rats inflicted with 30% TBSA full thickness scalding. It was found that the maximal binding capacity of the insulin receptors was greatly decreased(P