Ultrastructural localization of motilin in endocrine cells of human and dog intestine by the immunogold technique.

Motilin-immunoreactivity has been localized by two electron immunocytochemical techniques, using gold-labelled protein A or IgG as second layer, in a specific type of endocrine cell scattered in the epithelium of human and canine upper small intestine. The motilin (M) cell is characterized by relatively small (180 nm in man; 200 nm in the dog), solid granules with homogeneous core and closely applied membrane, round in man, round to irregularly-shaped in the dog. Perinuclear microfilaments are prominent in human motilin cells.