Fluorescence histochemistry of peptide hormone-producing cells: observations on the phenanthrenequinone method for the demonstration of arginine residues.

Phenanthrenequinone is a sensitive and specific fluorescence histochemical reagent for monosubstituted guanidines. It is probable that it selectively demonstrates the guanidino group of arginine residues of proteins and peptides. Phenanthrenequinone induces moderate to intense fluorescence in gastric chief cells, parenchymal cells of the pancreas, and certain peptide hormone-producing cell types such as the GH cells of the adenohypophysis and the glucagon cells of the pancreatic islets. Similar fluorescence spectra were obtained from an arginine-containing peptide in a histochemical model and from the GH cells of the adenohypophysis following exposure to phenanthrenequinone. We conclude that the cells demonstrated with this reagent store peptides or proteins rich in arginine.