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Large doses of intraperitoneally injected basic amino acids, L-arginine, or L-ornithine, induce acute pancreatitis in rodents, although the mechanisms mediating pancreatic toxicity remain unknown. Another basic amino acid, L-lysine, was also shown to cause pancreatic acinar cell injury. The aim of the study was to get insight into the mechanisms through which L-lysine damages the rat exocrine pancreas, in particular to characterize the kinetics of L-lysine-induced mitochondrial injury, as well as the pathologic responses (including alteration of antioxidant systems) characteristic of acute pancreatitis.We showed that intraperitoneal administration of 2 g/kg L-lysine induced severe acute necrotizing pancreatitis. L-lysine administration caused early pancreatic mitochondrial damage that preceded the activation of trypsinogen and the proinflammatory transcription factor nuclear factor-κB (NF-κB), which are commonly thought to play an important role in the development of acute pancreatitis. Our data demonstrate that L-lysine impairs adenosine triphosphate synthase activity of isolated pancreatic, but not liver, mitochondria.Taken together, early mitochondrial injury caused by large doses of L-lysine may lead to the development of acute pancreatitis independently of pancreatic trypsinogen and NF-κB activation.

OBJECTIVE: Intraperitoneal administration of large doses of l-arginine is known to induce severe acute pancreatitis in rats. We therefore set out to determine whether metabolites of l-arginine (l-ornithine, l-citrulline, and nitric oxide) cause pancreatitis. DESIGN: The authors conducted an in vivo animal study. SETTING: This study was conducted at a university research laboratory. SUBJECTS: Study subjects were male Wistar rats. INTERVENTIONS: Dose–response and time course changes of laboratory and histologic parameters of pancreatitis were determined after l-arginine, l-ornithine, l-citrulline, or sodium nitroprusside (nitric oxide donor) injection. MEASUREMENTS AND MAIN RESULTS: Intraperitoneal injection of 3 g/kg l-ornithine but not l-citrulline or nitroprusside caused severe acute pancreatitis; 4 to 6 g/kg l-ornithine killed the animals within hours. Serum and ascitic amylase activities were significantly increased, whereas pancreatic amylase activity was decreased after intraperitoneal injection of 3 g/kg l-ornithine. The increase in pancreatic trypsin activity (9–48 hrs) correlated with the degradation of IκB proteins and elevated interleukin-1β levels. Oxidative stress in the pancreas was evident from 6 hrs; HSP72 synthesis was increased from 4 hrs after l-ornithine administration. Morphologic examination of the pancreas showed massive interstitial edema, apoptosis, and necrosis of acinar cells and infiltration of neutrophil granulocytes and monocytes 18 to 36 hrs after 3 g/kg l-ornithine injection. One month after l-ornithine injection, the pancreas appeared almost normal; the destructed parenchyma was partly replaced by fat. Equimolar administration of l-arginine resulted in lower pancreatic weight/body weight ratio, pancreatic myeloperoxidase activity, and histologic damage compared with the l-ornithine-treated group. l-ornithine levels in the blood were increased 54-fold after intraperitoneal administration of l-arginine. CONCLUSIONS: We have developed a simple, noninvasive model of acute necrotizing pancreatitis in rats by intraperitoneal injection of 3 g/kg l-ornithine. Interestingly, we found that, compared with l-arginine, l-ornithine was even more effective at inducing pancreatitis. Large doses of l-arginine produce a toxic effect on the pancreas, at least in part, through l-ornithine. (Crit Care Med 2008; 36:2117–2127)

AIM: To assess the effect of our novel cell-permeable nuclear factor-kappaB (NF-kappaB) inhibitor peptide PN50 in an experimental model of acute pancreatitis. PN50 was produced by conjugating the cell-penetrating penetratin peptide with the nuclear localization signal of the NF-kappaB p50 subunit. METHODS: Pancreatitis was induced in male Wistar rats by administering 2X100 mug/kg body weight of cholecystokinin-octapeptide (CCK) intraperitoneally (IP) at an interval of 1 h. PN50-treated animals received 1 mg/kg of PN50 IP 30 min before or after the CCK injections. The animals were sacrificed 4 h after the first injection of CCK. RESULTS: All the examined laboratory (the pancreatic weight/body weight ratio, serum amylase activity, pancreatic levels of TNF-alpha and IL-6, degree of lipid peroxidation, reduced glutathione levels, NF-kappaB binding activity, pancreatic and lung myeloperoxidase activity) and morphological parameters of the disease were improved before and after treatment with the PN50 peptide. According to the histological findings, PN50 protected the animals against acute pancreatitis by favoring the induction of apoptotic, as opposed to necrotic acinar cell death associated with severe acute pancreatitis. CONCLUSION: Our study implies that reversible inhibitors of stress-responsive transcription factors like NF-kappaB might be clinically useful for the suppression of the severity of acute pancreatitis.

AIM: To determine the effect of melatonin pre- and post-treatment on the severity of L-arginine (L-Arg) -induced experimental pancreatitis in rats. METHODS: Male Wistar rats (25) were divided into five groups. Those in group A received two injections of 3.2 g/kg body weight L-Arg i.p. at an interval of 1 h. In group MA, the rats were treated with 50 mg/kg body weight melatonin i.p. 30 min prior to L-Arg administration. In group AM, the rats received the same dose of melatonin 1 h after L-Arg was given. In group M, a single dose of melatonin was administered as described previously. In group C the control animals received physiological saline injections i.p. All rats were exsanguinated 24 h after the second L-Arg injection. RESULTS: L-Arg administration caused severe necrotizing pancreatitis confirmed by the significant elevations in the serum amylase level, the pancreatic weight/body weight ratio (pw/bw), the pancreatic IL-6 content and the myeloperoxidase activity, relative to the control values. Elevation of the serum amylase level was significantly reduced in rats given melatonin following L-Arg compared to rats injected with L-Arg only. The activities of the pancreatic antioxidant enzymes (Cu/Zn-superoxide dismutase (Cu/Zn-SOD) and catalase (CAT)) were significantly increased 24 h after pancreatitis induction. Melatonin given in advance of L-Arg significantly reduced the pancreatic CAT activity relative to that in the rats treated with L-Arg alone. In the liver, L-Arg significantly increased the lipid peroxidation level, and the glutathione peroxidase and Cu/Zn-SOD activities, whereas the Mn-SOD activity was reduced as compared to the control rats. Melatonin pre-treatment prevented these changes. CONCLUSION: Melatonin is an antioxidant that is able to counteract some of the L-Arg-induced changes during acute pancreatitis, and may therefore be helpful in the supportive therapy of patients with acute necrotizing pancreatitis.