An improved method for extracting myeloperoxidase and determining its activity in the pancreas and lungs during pancreatitis

Objectives: This study was undertaken to examine the cause of variation in determined values of myeloperoxidase activity from sequestered neutrophils in pancreas and lungs during pancreatitis and to develop a reproducible method for the extraction and measurement of myeloperoxidase in these tissues. Methods: We measured myeloperoxidase in pancreatic and lung homogenates at different steps and evaluated the extent of inhibitory activity by measuring enzyme activity in the presence of homogenates from normal lungs and pancreata. To remove inhibitory activity from the homogenates, different methods like heat inactivation, inclusion of catalase inhibitor, and membranous pellet washing were evaluated. Results: Significant myeloperoxidase inhibitory activity was observed in pancreatic and lung homogenates, which could be effectively removed by the newly developed protocol. In extracts, myeloperoxidase activity can be determined by a spectrophotometric method, which is not only reproducible but is also adoptable for use in a plate reader or an autoanalyzer. Using this method, we studied the pattern of neutrophil sequestration over time in both pancreatic and lung tissue during caerulein-induced pancreatitis. Conclusions: Myeloperoxidase inhibition in the pancreas and lungs contributes to the variation observed in measurement of the enzyme.