Background Nitric oxide is a key signalling molecule in the pathogenesis of inflammation, but its role in acute pancreatitis and related abdominal pain induced by secretory phospholipase A2 (sPLA2) from Crotalus durissus terrificus (Cdt) venom has not been investigated. Methods Male Wistar rats were i.v. injected with L-NAME (20?mg/kg), aminoguanidine (AG, 50?mg/kg), 7-nitroindazole (7-NI, 10?mg/kg) or vehicle 10?min before or 60?min after the injection of sPLA2 (300?μg/kg) into the common bile duct. After 4?h of sPLA2 injection, abdominal hyperalgesia and inflammation were assessed in addition to serum amylase, nitrite/nitrate (NOx), pancreas lipoperoxidation and 3-nitrotyrosine (3-NT) contents. Results sPLA 2-induced acute pancreatitis, related abdominal hyperalgesia, hyperamylasemia and increased concentration of NOx were not correlated with lipoperoxidation or increased 3-NT in the pancreas. Pretreatment with all the nitric oxide synthase (NOS) inhibitors significantly reduced abdominal mechanical hyperalgesia, but only iNOS blockade by AG suppressed pancreas oedema and serum NOx increase. The therapeutic approach with all the NOS inhibitors produced a similar reduction pattern of the abdominal hyperalgesia, but AG treatment also inhibited serum hyperamylasemia and NOx concentrations and pancreatic myeloperoxidase. The nNOS blockade by 7-NI treatment also inhibited myeloperoxidase activity in both pancreas and lung. 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