Diamine oxidase-gold enzyme-affinity ultrastructural demonstration that human gut mucosal mast cells secrete histamine by piecemeal degranulation in vivo

Biopsy specimens of human ilea were prepared for the ultrastructural detection of histamine in vivo with a new enzyme-affinity method (Dvornak et al., J Histochem Cytochem 1993; 41:787-800). Human gut mucosal mast cells contained histamine in cytoplasmic secretory granules that were electron dense, regardless of underlying substructural patterns. Partially and completely empty cytoplasmic granules, characteristic for piecemeal degranulation (Dvorak et al., Int Arch Allergy Immunol 1992;99:74-83) had diminished and absent histamine stores, whereas electron-dense grannies in the same cells retainer! there histamine. Interstitial collagen (but not basal lamina of other cells) near secretory mad cells avidly bound histamine, thereby providing a potential source for re-release of extracellular histamine stores, These studies provide the first documentation of histamine secretion in vivo during piecemeal degranulation of human mast cells.