Abstract: Objective: To explore the mechanism of acute renal injury in severe acute pancreatitis (SAP). Methods: Fifty-four SD rats were randomly divided into a sham operation group (n=24) and a SAP group (n=30). The SAP model was induced by injection of 5% sodium taurocholate solution into the bilo-pancreatic duct. Rats from each group were killed, and the serum and ascites were collected 6, 12, 24h after the operation. TNF-αlevel of serum and ascites was measured by enzyme linked immuno-sorbent assay (ELISA). The expression of TNF-αmRNA and apoptosis rate of kidney tissue in both groups were assessed by RT-PCR analysis and TUNEL stain. The serum and ascites that had been collected 24 hours after development were injected into a medium of NRK cell, and then the level of TNF-αsecreted by the NRK cells was measured after injection 6, 12, 24h, and the cell apoptosis was also evaluated after injection 24h. The level of TNF-αwas assessed by an enzyme linked immuno-sorbent assay (ELISA). The expression of TNF-α mRNA was detected by reverse transcription polymerase chain reaction (RT-PCR). NRK cell apoptosis was evaluated by flow cytometry (FCM). Results： ①The serum and ascites levels of TNF-α were significantly elevated in the SAP groups compared with the sham operation groups at all time points(P<0.01), and considerably differed in SAP groups between any two time points(P<0.05). The expression level of TNF-αmRNA in renal tissue was more dramatically up-regulated than that in the sham operation group. The morphology of renal tissue was normal in the sham operation groups, on the other hand, obvious interstital hyperemia and edema and neutrophil infiltration were observed in the SAP group, in particular, being severe at the 24h time point; ②The level of TNF-αproduced by the NRK cells increased more significantly at 12h than that at 6h, also was higher at 24h than at 12h after injection of serum and ascites at 24h′s SAP(P<0.05).　Moreover, the ascites-induced groups were more obviously elevated than the serum-induced groups. NRK cells became thin and long at 6h, intracelluar granules increased at 12h and cells deformed at 24h when being disposed by the serum and ascites of SAP. In SAP groups, the apoptosis ratio of ascites-induced NRK cells was 56.95% and of serum-induced groups was 27.27% at 24h, and in the sham operation group, they were 3.72% and 4.11% (P<0.001), respectively. Thereafter, the index of apoptosis NRK cells appeared to increase transiently (ascites-induced groups: 12.3%, serum-induced groups: 8.1%, pre-induced groups: 3.8%, P<0.05). Conclusion： Over apoptosis of NRK cells is possibly involved in the mechanism of renal injury during SAP, and TNF-αis one of the major factors inducing the NRK cell apoptosis. Ascites plays a more important role in renal injury than serum during SAP.

Key words: Pancreatic diseases, Tumor necrosis factor, Kidney failure, acute, Apoptosis