Histochemical characterization of a tryptamine-like substance stored in cells of the mammalian adenohypophysis.

A recently developed, sensitive fluorescence method for the histochemical localization and the microspectrofluorimetric characterization of tryptamine (Bjorklund, Falck and HBkanson 1968) has been applied to the pituitary gland of the rat, cat, and pig. In all three species, most of the cells of the pars intermedia and many cells in the pars distalis were found to store a substance in the cytoplasm that could be transformed to a highly fluorescent derivative under the special reaction conditions required to obtain a high fluorescence yield of tryptamine. This pituitary fluorophore, moreover, showed the same microspectrofluorimetric characteristics under various conditions as does the tryptamine fluorophore. These histochemical and microspectrofluorimetrc characteristics differ clearly from those exhibited by a number of catechol and indole compounds, including the biogenic catecholamines, 5-hydroxytryptamine and tryptophan. The reliability and the significance of the histochemical criteria are discussed, and it is concluded that there is much to support the view that tryptamine, or a closely related β(3–1ndolyl)ethylamine, is stored in the adenohypophysis. Another fluorophore that may derive from a hitherto unknown biogenic phenylethylamine was disclosed in a large number of pars distalis cells not identical with those that possibly store tryptamine.