MERKEL CELL - MEMBER OF THE APUD CELL SYSTEM - FLUORESCENCE AND ELECTRON-MICROSCOPIC CONTRIBUTION TO THE NEUROTRANSMITTER FUNCTION OF THE MERKEL CELL GRANULES

Merkel cells of sinus hair follicles of nude mice were investigated by fluorescence and electron microscopy following pretreatment with amine precursors (L-Dopa, L-5-Hydroxytryptophan) and monoaminoxidaseinhibitors (Marsilid, Harmaline). Neither in control animals nor in pretreated animals any evidence for an involvement of Merkel cells in monoamine metabolism could be found. Therefore, the hypothesis that Merkel cells might share the most constant cytochemical characteristics of the cells of the APUD series, i.e., to take up amine precursors, should definitely be left. Following Harmaline treatment, however, Merkel cells were found fluorescent; cytophotometric analysis of the fluorescence emission spectra of formaldehyde-treated and untreated tissue ascertained that this fluorescence was due merely to a specific Harmaline fluorescence. The significance of Harmaline uptake in Merkel cells, most probably in the Merkel cell granules, is discussed. © 1979 Springer-Verlag.