Cerium-based histochemical demonstration of oxidative stress in taurocholate-induced acute pancreatitis in rats: A confocal laser scanning microscopic study

Direct in vivo histological detection of oxygen-derived free radicals (OFRs ) in inflammatory conditions is not fully resolved. We report an applicatio n of cerium histochemistry (in which capture of OFRs by Ce atoms results in laser-reflectant cerium-perhydroxide precipitates) combined with reflectan ce confocal laser scanning microscopy (CLSM) to demonstrate the evolution o f oxidative stress in taurocholate-induced acute pancreatitis (AP) in rats. Animals were perfused with CeCl3 in vivo and cryostat sections of pancreat a were studied by CLSM. Vascular endothelium was immunolabeled for PECAM-1. OFR production by isolated polymorphonuclear leukocytes (PMNs) incubated i n vitro with CeCl3 was quantified by image analysis. In the pancreas, stron g OFR-derived cerium reflectance signals were seen in acinar cells at 1-2 h r, capillaries and small venules were frequently engorged by cerium precipi tates, and adherent PMNs presented weak intracellular reflectance signals. At 8-24 hr, acinar cell OFR production decreased, whereas adherent/transmig rated PMNs displayed abundant intra- and pericellular reflectance. PECAM-1 expression was unchanged. PMNs from ascites or blood showed significant (p< 0.01) time-dependent OFR production, plateauing from 2 hr. The modified cer ium capture/CLSM method allows the co-demonstration of in vivo oxidative st ress and cellular structures labeled with fluorescent markers. In vivo oxid ative stress was shown histologically for the first time in experimental AP .