Histochemical demonstration of glucagon and serotonin by a fluorescent method in the rat submaxillary gland.

: The submaxillary glands of young rats were examined in vivo and in vitro. Yellow fluorescence in some cells treated with o-phthalaldehyde was observed and they yielded a positive reaction on staining with phosphotungstic acid haematoxylin indicating the presence of glucagon. These cells were localized between secretory endpieces of the gland. In rats treated with L-5-hydroxytryptophan (L-5-HTP) cells similar in shape and size showed yellow fluorescence after the action of formaldehyde vapour. The results of histochemical studies and ultrastructural analysis seem to indicate the presence of cells similar to APUD endocrine cells in the rat submaxillary gland.