Formaldehyde-induced fluorescence as a means for differentiating epinephrine cells from norepinephrine cells in adrenal medulla

The Falck and Hi Harp technique for the cellular localization of catecholamines by formaldehyde-induced fluorescence was applied to rat, mouse, and Syrian hamster adrenal. Some medullary cells revealed an unexpected orange-brown fluorescence. In guinea pig or rabbit adrenals, which store predominantly epinephrine, orange-brown fluorescence was not readily observed. It was found in Syrian hamsters only at the medullary periphery, where norepinephrine-producing cells are known to occur. Orange-brown fluorescence was depleted by administration of reserpine and intensified by nialamide plus DOPA. The same cell clusters which stained specifically for norepinephrine with ferric ferricyanide were found in adjacent sections to exhibit orange-brown fluorescence. Only by reducing the temperature of the formaldehyde reaction could sections of hamster adrenal showing only yellow-green fluorescence be obtained. These data suggest that the orange-brown fluorescence might result from' polymerization, oxidation, or both, of the isoquinoline produced by the norepinephrine-formaldehyde reaction under conditions slightly more vigorous than optimal and in the presence of high concentrations of norepinephrine.