In this project we examine the potential of pathologic conditions of the vascular and pulmonary systems to oxidatively modify proteins and thus impair function of these tissues. Oxidative modification of proteins occurs when oxygen-derived free radicals attack proteins, causing the introduction of carbonyl groups into the amino acid side chains. Damage to the vascular endothelium as the result of ischemia/reperfusion (stroke) is examined in a tissue culture model of bovine pulmonary artery endothelial cells. Cells are exposed to exogenous metal-catalyzed oxidation systems or to an endogenous challenge of anoxia/reoxygenation. Cellular damage is assessed by: (1) Protein modification as monitored by reaction of dinitrophenyhydrazine (DNPH) with carbonyl groups, (2) Viability of cells by trypan blue exclusion, and (3) Activity of key cellular enzymes such as glucose 6-phosphate dehydrogenase. The ability of various antioxidants (catalase, superoxide dismutase) to prevent endothelial cell damage are also monitored by these criteria. The oxidative modification of proteins in pulmonary lung tissue is studied. Some disease states, such as cystic fibrosis, cause an increase in the oxidative stress of the lungs. By monitoring the degree of protein oxidation in lung tissue, particularly the lavage fluid, we hope to establish a tool to evaluate the efficacy of therapies being developed by the Pulmonary Branch of the NHLBI.