LOCALIZATION OF NITRIC-OXIDE SYNTHASE IMMUNOREACTIVITY IN MAST-CELLS OF HUMAN NASAL-MUCOSA

Nitric oxide (NO)-synthase immunoreactivity has been detected for the first time in mast cells of human normal nasal mucosa, with an antibod y specific for neuronal NO-synthase, Intense immunoreactivity was reve aled in secretion granules of mast cells but was found in mast cell gr anules free in the extracellular matrix only in some instances; no rea ctivity was found in the cytoplasm of this or other cell types. These findings suggest that human nasal mast cells contain a particulate iso form of NO-synthase, which shares epitopes with neuronal NO-synthase a nd is rapidly removed from granules upon exocytosis.