The behaviour of the nasal mucosa towards blood borne colloidal carbon in experimental animals.

A single dose of 8-16 mg of carbon C11/1431a was injected intravenously into rats, guinea-pigs, mice, goats and two pigs. Examination with the naked eye, dissecting microscope, light microscope and electron microscope of tissues from these animals sacrificed minutes, hours, weeks and up to 23 months after the injection revealed phogocytosis of most of the infected carbon by the professional phagocytes of the reticuloendothelial system (RES). However, in the non-RES sites carbon was trapped in significant amounts in the endothelial cells, the interendothelial spaces, pericytes and perivascular macrophages of the subepithelial capillaries and venules in the anterior nasal mucosa. The catchment area often showed partially fenestrated capillaries and redundant porous basement membrane around the venules. The leakage of carbon through these vessels was through these vessels was thought to be caused partly by the unusual porosity of the vascular walls and partly due to vascular stasis induced by constant loss of heat to the inspired air stream in post-natal life. The importance of these findings in the predilective localization of several granulomatous diseases and various forms of vasculitis in the nasal mucosa id discussed.