Ischemia reperfusion of the pancreas: a new in vivo model for acute pancreatitis in rats.

Based on the concept that ischemia is an important factor in the pathogenesis of acute pancreatitis, we developed a new model of complete ischemia/reperfusion of the pancreas in the rat. The aim of this study was to investigate the microcirculation of the pancreas after complete and reversible ischemia at different times after reperfusion by using intravital fluorescence microscopy. In addition, the effect of ischemia/reperfusion on the pancreas was assessed by means of light and electron microscopy and measurement of serum pancreas amylase concentration. In 35 adult Sprague-Dawley rats ischemia of the pancreas was induced by temporary occlusion of the four supplying arteries. Sham-operated animals served as controls (group A). After periods of 30 min (group B), 60 min (group C) or 120 min (group D) of ischemia the organ was reperfused. To exclude the influence of hypovolemia on microcirculation in group E (120 min ischemia) hydroxyethylstarch (HES) was given i.v. to maintain central venous pressure at baseline values. For intravital fluorescence microscopy the pancreas was exteriorized on a stage and quantitative analysis of microcirculation, including functional capillary density and leukocyte-endothelium interaction, was performed after 30 min, 1 h and 2 h of reperfusion. Serum pancreas-amylase was measured at control (prior ischemia) and at 2 h after reperfusion. Tissue samples for light and electron microscopy were taken 2 h after reperfusion. In sham-operated animals, functional capillary density (FCD) remained within baseline values (FCD 407.7 +/- 9 cm-1) during reperfusion. Dependent on the time of ischemia and time of reperfusion a gradual reduction in functional capillary density was observed; after 2 h of ischemia only 35% of capillaries were perfused (FCD 140.9 +/- 28.3 cm-1). Reduced functional capillary density was associated with an increase of perfusion heterogeneity to a maximum of 0.65 +/- 0.12, as against 0.13 +/- 0.02 in control animals. With a 2 h ischemia leukocyte-endothelium interaction was enhanced after 0.5 h of reperfusion (8-fold increase of adherent leukocytes in comparison to control) followed by a further significant increase until 2 h after the beginning of reperfusion. Amylase concentration after ischemia of 2 h (2967 +/- 289 U/l) was significantly higher as compared to controls (1857 +/- 99 U/l). Differences between group E and D were not observed. Pancreatic tissue injury was ascertained by histopathological studies. These results indicate that complete ischemia/reperfusion of the pancreas induces pancreatic microvascular failure. The severity of changes depends on duration of ischemia and duration of reperfusion. The morphological and biochemical changes suggest that ischemia/reperfusion causes an inflammatory reaction as observed in acute pancreatitis.