Fluorescamine as a histochemical reagent: demonstration of polypeptide hormone-secreting cells

Fluorescamine is a useful fluorescence microscopic reagent for the demonstration of certain peptide hormone-secreting cells in formaldehyde-fixed tissues. Among the cells demonstrated are the pituitary GH cells, the gastrin cells, the insulin cells and the thyroid C cells. In the latter cell system degranulation brings about a marked decrease in the intensity of the fluorescamine-induced fluorescence suggesting that the fluorogenic component is associated with the secretory granules. In models neither of the hormones tested--GH, gastrin, insulin--gave fluorescamine-induced fluorescence after pretreatment with formaldehyde. It is suggested that the fluorescamine-induced fluorescence of the endocrine cells demonstrates granular components distinct from the hormones.