Abstract
After intravenous injection of colloidal carbon, subcutaneous injection of bradykinin (BK, 5-5000 ng/50μl) into the scrotum of rats induced carbon deposit along the venular trees of the cremaster muscle, since BK induced the gap formation between endothelial cells of venules. Endothelial cells of the collecting venules were most sensitive to BK and kept the gaps open longer than 20 min, whereas venules upstream with a diameter of about 10μm were less sensitive and closed the gaps within 5 min. Thus, individual endothelial cells show different sensitivity along the venular trees within a distance of 400 to 500 μm. Vital microscopy of microcirculation of hamster cheek pouch disclosed that polymorphonuclear leukocytes (PMNs) cross the endothelial layer to the interstitial space by four steps; adhesion to endothelial cells, penetration between adjacent endothelial cells, stay beneath the pericyte basement membrane (BM) and cross the pericyte BM. The experiments revealed that the adhesion of PMNs by LTB4 was attributable to change in the PMN membrane and not to that in the vascular endothelial cells. Thus, the endothelial cells seem to take a passive role to the PMN penetration. Rapid and magnificent development of the techniques in culturing endothelial cells must be supplemented with the knowledge, which was aquired by in vivo observation and precise analyses of the nature of the endothelial cells in living animals under the microscope.
