PRESENCE AND LOCATION OF ENDOTHELIN AND ENDOTHELIN-BINDING SITES IN HUMAN NASAL-MUCOSA UNDER NORMAL AND METAPLASTIC CONDITIONS

The presence and site of production of endothelin-1 (ET-1) was investi gated in biopsies obtained from the nasal mucosa of 10 healthy human s ubjects and 10 patients affected by chronic rhinitis. The presence and localization of receptors for ET-1 was also investigated. Bioptic fra gments were examined by scanning electron microscopy. ET-1 was present in the vessels and in the respiratory epithelium of normal subjects, whereas in patients affected by epithelial metaplasia induced by chron ic rhinitis, it was absent in the metaplastic epithelium and present i n the endothelium and vascular wall. Receptors for ET (A- and B-recept or subtypes) were localized in the vessels of the nasal mucosa, both i n normal and in pathological subjects. In particular, A-receptors were identified in the vascular wall, whereas B-receptors were mainly dist ributed in the endothelium. We suggest that ET-1 is involved in the ho meostasis of nasal blood flow (shunting the blood toward the deep cave rnous plexus and inducing mucosal swelling) by an autocrine and/or par acrine mechanism. Normal epithelium seems to be important in this mech anism, since it is able to produce ET. However, when pathologic condit ions induce squamous or cuboidal metaplasia, the epithelium is no long er able to play this role.