Vascular permeability in the rat gingiva. A model of vessel response in chronic inflammation.

The vascular permeability of the vessels of clinically normal gingiva of rats was studied using the colloidal carbon technique. The connective tissue situated underneath the keratinised epithelium was normal, but that subjacent to the non-keratinised epithelium showed some degree of chronic inflammation and as a rule the vessels of the area exhibited increased vascular permeability. In the buccal gingiva the vessels labelled with carbon form loops situated 200 micrometers below the marginal gingiva, while in the interdental gingiva the altered vessels are just below the superficial epithelium. On electron microscopy the vessels in the inflamed areas showed many open endothelial junctions, and also pseudo-fenestration, and endoplasmic vesicles full of carbon. Little is known about vascular changes in chronic inflammation, and the rat gingiva seems to be a suitable model for their study.