Increased peritoneal permeability in acute experimental pancreatitis

Antioxidant and calcium channel blockers counteract endothelial barrier injury induced by acute pancreatitis in rats

BACKGROUND

Multiple organ failure is the major mortality-related complication in severe acute pancreatitis. Endothelial barrier injury may be involved in its pathophysiology.

METHODS

The present study evaluated alterations in endothelial barrier integrity in different organs/tissues 12 h after induction of acute pancreatitis by intraductal infusions of bile. Potential effects of oxygen free radicals and calcium influx were evaluated by pretreatment with an antioxidant, N-acetyl-L-cysteine, and calcium channel antagonists, verapamil and diltiazem.

RESULTS

Tissue edema, reflected by an increase in tissue water content, was noted in the stomach, proximal small intestine, cecum, spleen, pancreas, kidneys, liver, lungs, heart, and brain in rats with pancreatitis. Also, an increased endothelial barrier permeability, as evidenced by the leakage of radiolabeled human serum albumin from blood to tissues, occurred in the stomach, proximal small intestine, colon, peritoneum, spleen, pancreas, kidneys, liver, lungs, and heart, accompanied by altered liver functions, increased levels of pancreatic enzymes, compromised renal function, and delayed intestinal motility. N-acetyl-L-cysteine prevented tissue edema and endothelial permeability changes in most organs/tissues, whereas the effects of verapamil and diltiazem were less marked. The preventive effects occurred in an organ-dependent manner.

CONCLUSIONS

Endothelial barrier injury is found in all investigated organs/tissues in acute experimental pancreatitis. Oxygen free radicals and calcium influx may play a role in the development of these changes.

Fibrinolytic enzymes in ascites during experimental acute pancreatitis in rats

The ascites accumulating during acute pancreatitis contain proteases that play a role in the progression of this disease. The proteases of the fibrinolytic system in the ascites were therefore studied in experimental acute pancreatitis induced in rats. Synthetic substrate assay and the fibrin plate method revealed high activities of proteases, including plasminogen activator, in the ascites. The plasminogen activator had a mol wt of about 50,000 by zymography. The plasminogen activator adsorbed on Lys-sepharose from the ascites was observed at the 100,000 mol wt position and in the 50,000-100,000 mol wt range on zymography and appeared at the 50,000 mol wt position after treatment by concentration. Its activity was enhanced by trypsin treatment. In other experiments, when incubated homogenate of normal pancreas lacking in zymographic activity was injected intraperitoneally into healthy rats, the recovered fluid displayed lytic zones between the 100,00 and 50,000 mol wt positions. These findings suggest that the ascites contained plasminogen activator, part of which was released by intrapancreatic substances and was present in the precursor form.

The resorption of FITC-dextran 10,000 from the peritoneum in different modifications of bile-induced acute pancreatitis and in bacterial peritonitis

The resorption from the peritoneum of fluorescein-isothiocyanate-conjugated (FITC) dextran with a mol wt of 10,000 was studied after 6, 15, and 24 h in rats with (1) only laparotomy (LC), (2) bacterial peritonitis (BP), (3) bile-induced acute pancreatitis (AP), (4) acute pancreatitis induced with contaminated bile (AIP), and (5) cerulein administration during acute pancreatitis (CAP). Animals in the AIP and CAP groups had a significantly higher mortality rate at 24 h and higher hematocrit at 6 h, indicating severe disease in these animals. At 6 and 15 h, all groups displayed similar peritoneal resorption. After 24 h, all groups with active inflammation showed significantly higher resorption than laparotomy controls. We conclude that peritoneal resorption as defined is independent of the severity and mode of induction of acute experimental pancreatitis and that it is the same as in bacterial peritonitis.

The role of ascites and phospholipase A2 on peritoneal permeability changes in acute experimental pancreatitis

Peritoneal permeability to fluorescein-isothiocyanate-conjugated (FITC) dextran, mol wt 10,000 was studied in acute experimental pancreatitis (AEP) in rats. The aim of the study was to elucidate the role of the pancreatitis ascites and its phospholipase A2 activity on the observed peritoneal permeability increase during AEP. Phospholipase A2 activity of ascites was 40 U/microL 1 h after the induction of AEP and decreased during the next 3 h gradually to a plateau of about 20 U/microL, where it remained to the end of the experiment at 24 h. A similar pattern was seen for protein, amylase, and lipase although the initial peak was most pronounced for lipase. Pancreatitis ascites did not--irrespective of its age (1 or 20 h) or incubation time (3-20 h)--affect the peritoneal transport of FITC dextran 10,000 in healthy rats. Similarly, intravenously-administered ascites and intraperitoneal instillation of pancreatic phospholipase A2 dissolved in saline were without effects. On the other hand, in another group of healthy animals, phospholipase dissolved in fresh pancreatitis ascites caused a statistically significant increase of peritoneal transport, as defined. In rats with pancreatitis, the addition of phospholipase A2 to the peritoneal fluid increased peritoneal transport of FITC dextran 10,000 as well as phospholipase A2 itself. We conclude that phospholipase A2 when instilled into the peritoneal cavity in the presence of pancreatitis ascites, has the ability to increase peritoneal permeability to FITC dextran 10,000 in healthy, as well as in pancreatitis rats. However, the phospholipase A2 activity of rat pancreatitis ascites is not sufficient for this mechanism to work. This, however, does not exclude its existence in other species, including humans.