Immunocytochemical localization of histamine in enterochromaffin-like (ECL) cells in rat oxyntic mucosa: A transmission electron microscopy study using monoclonal antibodies and conventional glutaraldehyde-based fixation

Histamine (HA), contained in the enterochromaffin-like (ECL) cells of the g astric mucosa in animals, plays an important role in gastric acid secretion , although methods for its exact morphological localization are still lacki ng. We used a pre-embedding indirect immunoperoxidase approach to define th e fine structural localization of HA in rat oxyntic mucosa that was fixed w ith a glutaraldehyde-based fixative a nd HA monoclonal a nti bod ies (MAbs AHA-1 and 2). Transmission electron microscopy showed that the peroxidase e nd-product not only was concentrated in the cores of cytoplasmic granules b ut also was distributed to a high degree in the cytoplasm peripheral to the granules of the ECL cells. These results suggest that in ECL cells HA is e nzymatically synthesized in the cytoplasm, then is transported and stored i n the cores of the granules before its release from the basal lamina. The p resent HA immunoelectron microscopic method with MAbs would be applicable m ore generally to the ultrastructural identification of HA-containing cells.