Aim: To analyze the capability of N-acetylcysteine (NAC) to prevent major intra-acinar pathogenic mechanisms involved in the development of acute pancreatitis (AP). Methods: AP was induced by pancreatic duct obstruction (PDO) in rats. Some animals received NAC (50 mg/kg) 1 h before and 1 h after PDO. During a 24-hour period of PDO, plasma amylase activity and pancreatic glutathione and malondialdehyde levels were measured. Cytosolic Ca²⁺ levels and enzyme (amylase and trypsinogen) load in acinar cells were also analyzed by flow cytometry, and histological analysis of the pancreas was performed by electron microscopy. Results: NAC avoided glutathione depletion at early AP stages, thereby preventing pancreatic oxidative damage, as reflected by normal malondialdehyde levels. By limiting oxidative stress, NAC treatment effectively prevented the impairment of Ca²⁺ homeostasis found in acinar cells from early AP onwards, thus protecting the pancreas from damage. In addition, lower quantities of digestive enzymes were accumulated within acinar cells. This finding, together with the significantly lower hyperamylasemia observed in these animals, suggests that NAC treatment palliates the exocytosis blockade induced by PDO. Conclusion: By preventing oxidative stress at early AP stages, NAC administration prevents other pathological mechanisms of AP from being developed inside acinar cells, thus palliating the severity of disease.

Cholecystokinin (CCK) has been suggested to be a contributory mediator in acute pancreatitis (AP). The aim of the present study was to assess the role of CCK in the development of oxidative stress at different stages of AP induced by pancreatic duct obstruction (PDO) in rats, using L364,718 (a potent CCK-receptor antagonist) to block CCK action. Intra-acinar oxygen free radical (OFR) generation was analysed by flow cytometry using dihydrorhodamine-123 as a fluorogenic dye. Parallel measurements of pancreatic levels of reduced glutathione (GSH) and of several parameters for the diagnosis of AP were performed in both untreated PDO rats and PDO rats receiving L364,718 (0.1 mg x 12 h(-1) x kg(-1)). Diagnosis parameters indicated a greater severity of AP in rats treated with the CCK antagonist. The increase in OFR generation observed in acinar cells up to 12 h after inducing AP was triggered at an earlier stages and reached higher values when L364,718 was administered. Accordingly, greater pancreatic GSH depletion was observed in rats with AP treated with the CCK antagonist. Two populations of acinar cells that were differentiated by flow cytometry, R1 and R2, showed similar behaviour with regard to OFR generation in PDO rats; however, R1 cells showed greater sensitivity to L364,718 administration, and thus OFR production was increased in R1 cells earlier than in R2 cells. In conclusion, CCK blockade anticipates and enhances the amount of OFR produced in acinar cells as a consequence of AP, thus leading to earlier development of and more severe disease. The detrimental effect of L364,718 in AP induced by PDO suggests that plasma CCK does not play a major role in the development of this AP model.

Current evidence suggests that alterations within acinar cells are responsible for the development of acute pancreatitis. After inducing acute pancreatitis in rats by pancreatic duct obstruction, we analysed, using flow cytometry, the progressive changes in cytosolic Ca2+ concentrations in individual acinar cells from the earliest stages to 48 h after obstruction to investigate whether parallel alterations in the homoeostasis of Ca2+ could be defined in the different acinar cells throughout the evolution of pancreatitis. Morphological alterations of the pancreas, related to the severity of the disease at different stages, were observed by electron microscopy. Hyperamylasaemia and progressively more severe alterations, such as vacuolization, dilatation of endoplasmic reticulum, accumulation of zymogen granules and reorientation towards basolateral membrane, were observed during the first 12 h after pancreatic obstruction. A significant increase in cytosolic Ca2+ concentration was measured at these stages in a particular type of acinar cells (R1) differentiated by flow cytometry with low forward scatter (FSC), whereas another representative group of cells (R2) with higher FSC values were able to maintain resting cytosolic Ca2+ concentrations up to 24 h after obstruction. Longer periods of pancreatic duct obstruction induced disturbances in Ca2+ homoeostasis in all acinar cells. A similar increase in cytosolic Ca2+ load was reached in both R1 and R2 cells when acute pancreatitis was completely developed. In conclusion, the homoeostasis of Ca2+ in acinar cells is asynchronously impaired during the development of acute pancreatitis; cells with higher FSC (R2) appear to be more resistant than R1 cells.

Current evidence suggests that alterations within acinar cells are responsible for the development of acute pancreatitis. After inducing acute pancreatitis in rats by pancreatic duct obstruction, we analysed, using flow cytometry, the progressive changes in cytosolic Ca2+ concentrations in individual acinar cells from the earliest stages to 48 h after obstruction to investigate whether parallel alterations in the homoeostasis of Ca2+ could be defined in the different acinar cells throughout the evolution of pancreatitis. Morphological alterations of the pancreas, related to the severity of the disease at different stages, were observed by electron microscopy. Hyperamylasaemia and progressively more severe alterations, such as vacuolization, dilatation of endoplasmic reticulum, accumulation of zymogen granules and reorientation towards basolateral membrane, were observed during the first 12 h after pancreatic obstruction. A significant increase in cytosolic Ca2+ concentration was measured at these stages in a particular type of acinar cells (R1) differentiated by flow cytometry with low forward scatter (FSC), whereas another representative group of cells (R2) with higher FSC values were able to maintain resting cytosolic Ca2+ concentrations up to 24 h after obstruction. Longer periods of pancreatic duct obstruction induced disturbances in Ca2+ homoeostasis in all acinar cells. A similar increase in cytosolic Ca2+ load was reached in both R1 and R2 cells when acute pancreatitis was completely developed. In conclusion, the homoeostasis of Ca2+ in acinar cells is asynchronously impaired during the development of acute pancreatitis; cells with higher FSC (R2) appear to be more resistant than R1 cells.