Abstract
Objective:Physiological shock leads to elevated levels of plasma factors that activate circulating leukocytes and endothelial cells, thereby compromising microvascular functions. The nature and source of these plasma-derived activators are unknown. To examine the possible origin of these factors, we homogenized rat internal organs and measured their activity on cardiovascular cells in vivoand in vitro. Methods:Fresh tissue samples from small intestine, spleen, heart, liver, kidney, adrenals, and pancreas were homogenized. Their ability to induce leukocyte pseudopod formation and nitroblue tetrazolium (NBT) reduction was tested and their impact in vivoon blood pressure, survival, and microvascular cell injury was examined. Results:A dramatic increase (p< 0.001) in leukocyte activation compared to controls was observed with pancreas homogenate but not with homogenates from the other organs. Leukocyte activation was induced by homogenates of other tissues only after prior incubation with substimulatory concentrations of pancreatic homogenate. Pancreatic serine proteases, trypsin and chymotrypsin, which did not stimulate leukocytes, also generated activity from other tissues. Leukocyte pseudopod formation could be significantly inhibited by adding the serine protease inhibitor 6-amidino-2-naphthyl p-guanidinobenzoate dimethanesulfonate (ANGD) during tissue homogenization (p< 0.001). Injection of pancreatic homogenate into rats led to increased plasma hydrogen peroxide levels and an instantaneous drop in mean arterial pressure that was often lethal. These responses were prevented by prior infusion of ANGD (p< 0.001). Intravital microscopy of the rat mesentery confirmed that superfusion of filtered pancreatic homogenate leads to significant increases in cell death (p< 0.05), as detected by propidium iodide, and hydrogen peroxide formation (p< 0.05), as determined by dichlorofluorescein diacetate (DCFH) fluorescence. Conclusion:These results suggest that pancreatic enzymes attack tissue and generate cellular activators that are associated with organ dysfunction in shock. Microcirculation (2000) 7, 183–192.