Hemoglobin as a tracer in hemodynamic pulmonary edema

Stroma-free hemoglobin is an electron-opaque molecule useful as a tracer for the ultrastructural stuty of pulmonary capillary permeability. After this tracer was infused into the isolated pulmonary lobe of the dog, the endothelial junctions of the capillaries, as revealed by electron microscopy, act like distensible pores, thus allowing the tracer to escape when the pulmonary artery pressure was raised above 50 millimeters of mercury.