Brain death impairs pancreatic microcirculation.

Brain death (BD) influences the quality of donor grafts in transplantation. To evaluate the impact of BD on pancreas grafts, we investigated the influence of BD on the microcirculation and histology of the pancreas in a rat model of explosive BD. A group of Wistar rats (n=7), rendered brain dead by inflating an intracranially inserted Fogarty catheter was compared with controls (CO) using intravital epifluorescence-microscopy over 4 h after BD induction; functional capillary density (FCD), leukocyte adherence (AL) in post-capillary venules, histology and pancreatic enzymes were investigated. Four hours after BD, FCD decreased (333 +/- 11 vs. baseline 444 cm/cm2 +/- 5 SEM; p<0.01) and showed lower values than CO (388 +/- 9 p<0.01). In BD, AL was increased (628 cells/mm2 +/- 110 SEM vs. baseline 123 +/- 32, and vs. CO 180 +/- 33; p<0.001). BD caused increased histological damage (CO 1.6 score-points +/- 0.7 SD vs. BD 8.3 +/- 7.1; p<0.05). Amylase was higher in BD (p<0.05) but did not reach pathological values. We show for the first time that BD causes relevant changes in pancreatic microcirculation, histology and leukocyte endothelial interaction which might have a serious impact on the function of grafts. New strategies for preventing this damage are therefore highly desirable in order to improve the outcome of pancreas transplantation.

Expression and regulation of calpain in rat pancreatic acinar cells.

INTRODUCTION: Calpains, cytosolic Ca(2+)-dependent cysteine proteases, are expressed in a variety of mammalian cells and have been found to participate in stimulus-secretion coupling in platelets and alveolar cells. AIMS: In pancreatic acinar cells, expression of calpains and their role in the secretory process have not yet been elucidated. Both subjects, therefore, were examined in the current study. METHODOLOGY: mu-calpain and m-calpain were detected immunochemically. Calpain activation was measured by fluorescence spectrophotometry and single-cell fluorometry using Suc-Leu-Leu-Val-Tyr-AMC as substrate. Amylase secretion and cell damage, characterized by lactate dehydrogenase release, were measured by colorimetric assays. RESULTS: Immunochemistry revealed cytoplasmic localization of both calpain isoforms. Immediately after increasing the cytosolic Ca(2+) concentration with ionomycin, a marked dose-dependent protease activation and cellular damage were observed. Inhibition of ionomycin-mediated enzyme activation through preincubation of cells with Ca(2+)-free medium, BAPTA-AM, or Z-Leu-Leu-Tyr-CHN(2) significantly reduced cell injury. Cholecystokinin (100 pM) also induced proteolytic activity, preceding cholecystokinin-stimulated amylase secretion. Protease activity and amylase release were significantly inhibited by Z-Leu-Leu-Tyr-CHN(2 ) retreatment. CONCLUSION: Calpains are expressed in pancreatic acinar cells and may participate in stimulus-secretion coupling. In addition, our study indicates that pathologic calpain activation may contribute to Ca(2+)-mediated acinar cell damage.