OBJECTIVE To explore the mechanism and effectiveness of inducing severe acute pancreatitis (SAP) with saline saturated hydrogen in rats. METHODS Based on a random number table, 54 Sprague-Dawley rats were divided into 3 groups: control, SAP and treatment (n = 18 each). The model of SAP was established by a retrograde injection of 5% sodium taurocholate into biliary-pancreatic duct. The treatment group received an injection of 5 ml/kg hydrogen-rich saline into tail vein at 1 h post-modeling. The control group underwent only pancreatic tipping. All rats were exsanguinated under anesthesia by aortal puncture after 24 hours. The serum levels of tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and interleukin-18 (IL-18) in 3 groups were measured by enzyme-linked immunosorbent assay (ELISA). The expression of TNF-αmRNA in pancreatic tissue was measured by reverse transcription (RT)-PCR. And intercellular adhesion molecule-1 (ICAM-1) in pancreatic tissue was measured by immunohistochemistry. The pancreatic tissues were harvested to examine the microscopic changes. The levels of malonic aldehyde (MDA), myeloperoxidase (MPO), superoxide dismutase (SOD) and glutathione (GSH) in pancreatic tissue was measured by specific kits. RESULTS The pathological scores of pancreatic tissue were significantly lower in the treatment group than those in the SAP group (9.7 ± 2.0 vs 13.2 ± 2.5, P < 0.05). The serum level of TNF-αwas significantly lower in the treatment group than that in the SAP group ((88 ± 17) vs (1171 ± 18) pg/ml, P < 0.05). And the serum levels of IL-6 and IL-18 were lower in the treatment group than those in the SAP group ((25.2 ± 5.9) vs (37.3 ± 4.6) ng/L, (401 ± 100) vs (439 ± 103) ng/L, both P < 0.05). As compared with the SAP group, the levels of MDA and MPO decreased significantly in the treatment group ((8.2 ± 2.8) vs (14.7 ± 2.7) nmol/mg, (0.040 ± 0.011) vs (0.170 ± 0.071) U/g, both P < 0.05). However, the levels of SOD and GSH significantly higher than those of the treatment group ((22.1 ± 1.3) vs (15.1 ± 1.7) U/mg, (4.8 ± 0.4) vs (2.5 ± 0.3) U/mg, both P < 0.05). The expressions of TNF-α mRNA and ICAM-1 in pancreatic tissues were lower than those of the treatment group (0.33 ± 0.17 vs 0.94 ± 0.31, 2.0 ± 0.4 vs 2.8 ± 0.8, both P < 0.05). CONCLUSION Hydrogen-rich saline can decrease the levels of inflammatory mediators and reduce the pathological damage of pancreas through the inhibition of oxidative stress.