Emigration of activated leukocytes augments transvascular permeability in mesenteric venules of rat

Effects of leukocyte adhesion and emigration on the microvascular permeability were analyzed by the combined use of high resolution transilluminated intravital microscopy and the epiilluminated fluorescent tracer imaging. After stimulating leukocytes by topical application of PAF-LPS or fMLP solution on the mesentery of a rat, a dynamic process of leukocyte emigration was visualized under high resolution transilluminated microscopic observation. When considerable emigration of leukocytes was observed, the same microvasculature was subjected to a permeability study to visualize the diffusional process of the FITC-labeled macromolecules under an epiilluminated fluorescent microscope. Dye diffusion was accelerated in the PAF-LPS or fMLP-treated group, and also a distinctly spotty leakage was observed in venules where successive adhesion and emigration of leukocytes were observed.