Synaptophysin-Like Immunoreactivity in Merkel Cells of Fetal Rat Skin

Margit Nindl, MD, Department of Dermatology, Faculty of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113 (Japan) To the editor, We would like to report on the synaptophysin-like immunoreactivity of Merkel cells in fetal rat skin at day 20 of gestation, as detected by double immunostaining [1]. Unfixed, frozen sections obtained from the barbate portion of fetal rats were first incubated with an MC-specific antikeratin antibody (RCK-102, Bio-Science Products AG), confirmed by immunoelectron microscopy [unpubl. data], and thereafter immunostained using an immunogold-silver staining technique. Washed in PBS, the sections were then incubated with a monoclonal antibody against synaptophysin (Boehringer, Mannheim). Using the ABC immunostaining technique, the final reaction product was developed with DAB. For negative controls the antisynaptophysin antibody was replaced by PBS. Single cells, scattered in the basal layer of the epidermis, as well as cells clustered in the outer root sheath of hair follicles, stained positively with the Merkel cell-specific antikeratin antibody applied in the first step. Incubation with the antisynaptophysin antibody revealed a positive staining reaction within the cytoplasm of these cells (fig. 1). Negative controls were negative.