POLYMORPHISM OF MERKEL CELLS IN THE RODENT PALATINE MUCOSA - IMMUNOHISTOCHEMICAL AND ULTRASTRUCTURAL STUDIES

Our pervious electron microscopic studies indicated that Merkel cells (MCs) in the gerbil palatine mucosa were polymorphic, possibly reflect ing different function, In order to verify and extend this evidence, t he shape of and the innervation to MCs in the palatine mucosa of six d ifferent species of rodents including the Mongolian gerbil and the rat were examined by immunohistochemistry and transmission electron micro scopy. Immunohistochemistry using anti-cytokeratin 20 (CK20) antibody revealed that in the gerbil palatine mucosa, approximately half of MCs were dendritic, Confocal laser scanning microscopy after double label ing with anti-cytokeratin and anti-POP 9.5 or anti-Na+/K+-ATPase beta 1 subunit antibodies indicated that most of the dendritic MCs (DMCs) i n these mucosae were free of innervation, Electron microscopy showed t hat all species of rodents examined contained abundant dendritic MCs a s well as roundish (oval to round) MCs (RMCs) with typical innervation , Secretory granules of the RMCs were usually concentrated at the syna ptic site, whereas those of the DMCs tended to accumulate in the tips of the cytoplasmic processes and in the cytoplasm facing the basal lam ina, Some MCs showed features intermediate between those of the RMC an d DMC. These results indicate that MCs in rodent palatine mucosae are consistently polymorphic, and that DMCs may represent a distinctive su bset with specific, presumably including endocrine and paracrine, func tions different from those of RMCs.