Argentaffin and other “endocrine” cells of the small intestine in the adult mouse. I. Ultrastructure and classification

Abstract

AbstractElectron microscopic examination of the epithelium of crypts and villi in the jejunum of the adult mouse revealed the existence of three main types of cells which may be classified within the group of argentaffin and other “endocrine” cells of the gastrointestinal tract.Sixty per cent of the cells are characterized by the presence of biconcave granules. They are referred to as biconcave granule cells (Type EC). While most granules are biconcave, some of them are spherical and may show a particulate structure. Those cells with 95% or more biconcave granules predominate in the crypt, while those with 50–75% predominate in villi. The cells of this type are considered by some authors to be true argentaffin or enterochromaffin cells.Thirty‐seven per cent of the cells have spherical dense granules, a few of which look like empty vesicles. However, because of the marked differences between the sizes of the granules, these cells are classified into two categories. Those with granules averaging 360 mμ in diameter are referred to as large spherical granule cells (Type L, 13%), while those with granules averaging 250 mμ in diameter, are referred to as small spherical granule cells (Type S, 24%). Both types are found in crypts and villi.Three per cent of the cells do not fit into these categories. All these uncommon cells contain spherical granules; and, in addition, some have oval ones; others show large halos; and still others include granules of different sizes and densities.The existence of several “endocrine” cell types suggests that they play different roles in the jejunum of the mouse.