Objective To investigate the protective effect and possible mechanisms of continuous infusion of norepinephrine in kidney of septic rats in the early stage.Methods Thirty healthy male SD rats of SPF level were randomly divided into five groups.Rats in control group were given intraperitoneal injection of saline and began a continuous infusion of saline (1 ml/h).Rats in LPS group and the intervention group (low-dose,medium-dose and high-dose norepinephrine group) were given intraperitoneal injection of LPS 10 mg/kg.LPS group began a continuous infusion of saline (1 ml/h) while low,medium and high dose groups began continuous infusion of different norepinephrine solution [(0.06,0.3,0.6 μg/(kg·min)].Rats were sacrificed after 24 hours infusion.We detected serum inflammatory cytokines [tumor necrosis factor (TNF)-α,interleukin(IL)-1β,IL-6 and IL-10] in 2 h and 6 h by ELISA.Rat serum CRP,Cr and BUN,swelling and membrane potential of kidney mitochondria and oxidative stress-related indicators were tested in 24 h.We also observed renal pathologic changes by electronic microscopy and biopsy.Results Compared with the control group,serum levels of TNF-α [(2 203.3 ± 1 028.7) pg/ml],IL-1β [(2 214.5 ±457.0) pg/ml],IL-6 [(7784.7 ±248.2) pg/ml] and IL-10 [(1 076.1 ±368.4) pg/ml] were statistically higher in LPS group in 2 h (P ＜ 0.05) ; CRP [(0.35 ± 0.24) mg/L],Cr [(30.8 ± 11.5) μ mol/L],BUN [(7.7 ± 1.8) mmol/L],NO [(1 057.4 ± 172.9) μmol/gprot] were statistically higher (P ＜ 0.01),membrane potential of kidney mitochondria (0.0464 ±0.018 5) decreased statistically (P ＜0.01).Compared with LPS group,serum levels of TNF-αt [(506.8 ±301.7) pg/ml],IL-lβ [(415.6 ± 178.0) pg/ml],and IL-10 [(381.7 ± 171.0) pg/ml] significantly decreased in low-dose group in 2 h (P ＜0.05),BUN [(5.2 ± 1.4)mmol/L] decreased (P ＜ 0.05),mitochondrial membrane potential (0.347 4 ± 0.152 6) increased in 24 h (P ＜ 0.05) ; serum levels of TNF-α [(323.9 ± 227.9) pg/ml],IL-1 β [(700.0 ± 246.2) pg/ml],and IL-10[(282.6 ± 134.4) pg/ml] significantly decreased statistically in medium-dose group in 2 h (P ＜0.05),CRP [(0.17 ± 0.08) mg/L] decreased statistically (P ＜ 0.01),mitochondrial membrane potential (0.377 5 ±0.143 7) increased in 24 h (P ＜0.05) ;serum levels of TNF-α [(378.7 ±89.8) pg/ml],IL-1β [(945.7 ±264.4) pg/ml] significantly decreased in high-dose group in 2 h (P ＜0.05),CRP [(0.19 ±0.12) mg/L] and Cr [(23.2 ±3.4) μmol/L] decreased in 24 h (P ＜0.05).Mitochondrial matrix coated fuzzy,vacuoles and coagulation were found in LPS group by electronic microscopy examination.Interstitial edema,monocyte-macrophage infiltration,glomerular shrinkage,tubular epithelial cell swelling,empty bubble degeneration were found in LPS group by microscopy examination.Pathological damage was alleviated in mediumdose group.Conclusion Continuous infusion of norepinephrine plays a protective role on renal function in rats with sepsis in the early stage.The intervention protect rat kidney by reducing levels of inflammatory cytokines,oxidative stress and mitochondrial damage.