IN-SITU CHARACTERIZATION OF MAST-CELLS IN THE FROG RANA-ESCULENTA

The number, distribution, and ultrastructural characteristics of mast cells were assessed in the tongue, heart, and kidney of the frog Rana esculenta. The density of tongue mast cells (253+/-45 mast cells/mm(2) ) was significantly higher than that of the heart (5.3+/-0.4/mm(2)) an d kidney (15.3+/-1.4/mm(2)). A striking feature of this study was the remarkable association of frog mast cells to nerves. The ultrastructur al study of the mast cell/nerve association demonstrated that mast cel ls were closely apposed to or even embedded in nerves. Mast cells were also physically associated with melanocytes even in the heart. Mast c ells were Alcian blue(+)/safranin(+) in the tongue and in the peritone um, whereas in the heart and in the kidney they were Alcian blue(-)/sa franin(+). The mast cells in the lamina propria of the gastrointestina l tract were Alcian blue(+)/safranin(-). The cytoplasm of frog mast ce lls was packed with numerous heterogeneous, membrane-bound granules. T he ultrastructure of these cytoplasmic granules was unique, being tota lly unlike any other previously described granules in other animal spe cies as well as in man. The histamine content/frog mast cell (approxim ate to 0.1 pg/cell) was approximately 30 times lower than that of huma n mast cells isolated from different tissues (approximate to 3 pg/cell ). A monoclonal anti-histamine antibody was used to confirm the ultras tructural localization of histamine in secretory granules in frog mast cells.