The Correlation Of The Substance Concentration In Vitreous Humor Of Drowned Male Rats And PMI Under The Different Temperature

Objective To investigate the correlation between the concentration changes of AST、Urea、AMY、Glu、Vit.C、Hx in the vitreous humor of dead male rats and PMI under different temperature in Xining area.Exploring the influence of temperature factors on related biochemical indicators in vitreous humor after death of organisms,and providing scientific basis for studying vitreous humor in different temperature environments on plateaus to infer the PMI.Methods 95 adult male SD rats(body weight 200±30g)were fed at an altitude of 2 260 meters for two weeks.90 male rats were drowned in double-distilled water and randomly divided into 3 groups(low temperature group:4°C;normal temperature group:20°C;high temperature group:30°C).Each group was further divided into 6 groups according to the time of death[3,6,9,12,18,24 H group]with 5 rats,and another 5 rats were taken as the control group,the 0h group(immediately after death).The vitreous humor was collected at the set time points for the three temperature groups and 0h after death for the control group.Before testing,the samples were thawed at room temperature,and the Beckman Coulter AU5800automatic biochemical analyzer was used to detect the concentrations of AST,Urea,AMY,and Glu in VH at different times after death.The Agilent 1260 II high performance liquid chromatograph was used to detect the concentrations of Vit.C and Hx in the VH of rats at different times after death.The results were expressed as mean±standard deviation,and one-way ANOVA is used for significance test,and Pearson test,quadratic,cubic and compound regression analysis are used to derive the regression equation and verify it.Results The concentration of AST,Urea,AMY,Glu,Vit.C,and Hx showed a downward trend with the increase of PMI(P<0.05).Under different temperature conditions,the concentrations of AST,Urea,AMY,Glu,Vit.C,and Hx at the same death time in the experimental group were different.Regression analysis shows:when the temperature is 4°c,the cubic regression equation r~2 of Glu is higher,and the correlation with PMI is better;when the temperature is 20°c,Urea cubic regression equation r~2 is higher,and it is more accurate for PMI inference;when the temperature is 30°c,the cubic regression equation r~2 of Hx is higher,which is more suitable for PMI inference.Conclusion Temperature has an effect on the concentration of substances in the vitreous humor of drowned male rats;Urea cubic regression equation is more suitable for inferring PMI at 20°c,and Glu cubic regression equation is more suitable for inferring PMI at 4°c;The concentrations of Vit.C,AST,Hx,and AMY show a downward trend with the extension of PMI,which can be used as comprehensive inference indicators.