Effect Of Hypertonic Sodium Fluid Resuscitation On Kidney Injury In Rats At The Early Stage Of Severe Scalded

1.ObjectivesSevere burn shock is considered to be one of the main causes of early renal dysfunction after burns,and the mortality rate of patients with acute renal injury(AKI)after secondary burn is significantly increased.The aim of this study is to explore the effect of hypertonic saline(HS,300mEq/L Na~+)resuscitation on kidney injury of scalded rats relates to lactated Ringer solution(LR)by comparing renal function,renal cell morphology,inflammation,oxidative stress,and signal transduction pathway.2.Materials and methodsFifty-six female SD rats,weighed(230±15)g,were randomized into 3 groups:sham-burn group(n=8),LR group(n=24),andHS group(n=24).All animals were catheterizated by tail vein after anesthetization.Rats in the sham group were submerged in room-temperature water without any fluid resuscitation,whereas those in the experimental group were scalded on the back with boiling water to cause a 30%TBSA burn trauma,and treated with LR and 300mEq/L HS via tail vein injection.Samples were collected at 2,8,and 24h after resuscitation,separately.Part Ⅰ:Effects of hypertonic saline resuscitation on plasma sodium,renal function,and renal cell morphology in severely scalded ratsThe concentration of plasma sodium,creatinine and BUN was measured using an automatic biochemical analyzer.Plasma levels of neutrophil gelatinase-associated lipocalin(NGAL)were measured using enzyme-linked immunosorbent assay(Elisa)kits for rats in accordance with the manufacturer’s instructions.The moisture content of kidney reflected by wet/dry weight(W/D)ratio was determined.The fixed renal tissue using 10%formaldehyde were use to observe the tissue cell morphology by HE staining method.Part Ⅱ:Effects of hypertonic saline resuscitation on inflammation and oxidative stress in severely scalded ratsPlasma levels of tumor necrosis factor alpha(TNF-α),interleukin 6(IL-6)and high mobility group protein B1(HMGB1)were measured using Elisa kits for rats.The MDA content and SOD activity in the kidney tissue were examined by commercial kits according to the instructions of the manufacturer.Part Ⅲ:Effects of hypertonic saline resuscitation on the activity of p38MAPK in the renal tissue of severely scalded ratsThe p38MAPK activity levels of renal tissue were measured by using Western blotting(Western Blot).The value of p-p38MAPK/p38MAPK was expressed the activity of p38MAPK.3.ResultPart Ⅰ:Compared to the LR group,plasma sodium concentration was significantly lower than that both in sham group and HS group in rats after severe burn injury(P<0.01).The levels of plasma creatinine,BUN,and NGAL in LR and HS group was significantly higher than that in sham group(P<0.01).After burn 2h,plasma creatinine levels were close between LR and HS group,but it shown differences at 8h and 24h.Plasma BUN levels of the two treatment group at 2h and 24h were appeared no difference.Plasma NGAL levels of LR group was significantly higher than that in HS group after burn injury(P<0.01).The renal W/D was increased in both the LR and HS groups after injury relative to that in the sham group and was higher in the LR group(P<0.01).The HE staining showed that there were the epithelial cells of renal tubules swelled and necrotized,narrow renal tubular lumen,and many inflammatory cell exudations in LR group,whereas these damage were milder in HS group.Pathological score of renal tubular injury showed that the score in LR group was significantly higher than sham group and HS group(P<0.05).Part Ⅱ:The plasma levels of TNF-αand IL-6 were significantly increased both in LR and HS groups relate to sham group.The plasma TNF-αand IL-6 in LR group was evidently increased contrasting to HS group(P<0.01).Plasma HMGB1 concentration was unaltered 2h after injury relative to that in the sham group but increased at 8 and24h after injury,and it was higher in LR group than that in HS group(P<0.01).Compared with sham group,the content of renal tissue MDA was significantly increased both in LR and HS groups.The MDA content in renal tissue of HS group were declined relative to that in the LR group(P<0.01).Compared with sham group,the content of renal tissue MDA in the two treatment groups were declined after severe burn injury(P<0.01).At 2,8,and 24h after injury,the MDA content of LR group was lower than that in the sham and HS group(P<0.01).Part Ⅲ:The p38MAPK activity in renal tissue of LR group and HS group were significantly increased relate to sham group(P<0.01).The value of p-p38MAPK/p38MAPK was expressed the activity of p38MAPK,and those were significantly higher in LR group than that in the sham and HS group(P<0.01).4.Conclusion(1)Resuscitation with HS can prevent hyponatremia,and alleviate renal dysfunction and the damage of renal tissue cells related to LR group in scalded rats.(2)Resuscitation with HS can reduce inflammatory recitation and kidney oxidative damage related to LR group in scalded rats.(3)Resuscitation with HS can reduce the activity expression of p38MAPK in renal tissue related to LR group in scalded rats.