ECL cell morphology

Using immunohistochemistry at the conventional light, confocal and electron microscopic levels, we have demonstrated that rat stomach ECL cells store histamine and pancreastatin in granules and secretory vesicles, while histi dine decarboxylase occurs in the cytosol. Furthermore the ECL cells display immunoreactivity for vesicular monoamine transporter type 2 (VMAT-2), syna ptophysin, synaptotagmin III, vesicle-associated membrane protein-2, cystei ne string protein, synaptosomal-associated protein of 25 kDa, syntaxin and Munc-18. Using electron microscopy in combination with stereological method s, we have evidence to suggest the existence of both an exocytotic and a cr inophagic pathway in the ECL cells. The process of exocytosis in the ECL ce lls seems to involve a class of proteins that promote or participate in the fusion between the granule/vesicle membrane and the plasma membrane. The g ranules take up histamine by VMAT-2 from the cytosol during transport from the Golgi zone to the more peripheral parts of the cells. As a result, they turn into secretory vesicles. As a consequence of stimulation (e.g., by ga strin), the secretory vesicles fuse with the cell membrane to release their contents by exocytosis. The crinophagic pathway was studied in hypergastri nemic rats. In the ECL cells of such animals, the secretory vesicles were f ound to fuse not only with the cell membrane but also with each other to fo rm vacuoles. Subsequent lysosomal degradation of the vacuoles and their con tents resulted in the development of lipofuscin bodies.