Endocardial endothelium in the rat : junctional organization and permeabilityEndocardial endothelium in the rat : junctional organization and permeability
Faculty of Pharmaceutical, Biomedical and Veterinary Sciences. Pharmacy
Faculty of Medicine and Health Sciences
Department of Pharmaceutical Sciences
Cell and tissue research. - Berlin
277(1994):3, p. 391-400
University of Antwerp
Selective permeability of endocardial endothelium has been suggested as a mechanism underlying the modulation of the performance of subjacent myocardium. In this study, we characterized the organization and permeability of junctional complexes in ventricular endocardial endothelium in rat heart. The length of intercellular clefts viewed en face per unit endothelial cell surface area was lower, and intercellular clefts were deeper in endocardial endothelium than in myocardial vascular endothelium, whereas tight junctions had a similar structure in both endothelia. On this basis, endocardial endothelium might be less permeable than capillary endothelium. However, confocal scanning laser microscopy showed that intravenously injected dextran 10000 coupled to Lucifer Yellow penetrated first the endocardial endothelium and later the myocardial capillary endothelium. Penetration of dextran 10000 in myocardium occurred earlier through subepicardial capillary endothelium than through subendocardial capillary endothelium. Penetration of tracer might thus be influenced by hydrostatic pressure. Dextran of MW 40000 did not diffuse through either endocardial endothelium or capillary endothelium. The ultrastructure df endocardial endothelium may constitute an adaptation to limit diffusion driven by high hydrostatic pressure in the heart. Differences in paracellular diffusion of dextran 10000, between endocardial endothelium and myocardial vessels, may result from differing permeability properties of the endocardium and underlying myocardium.