ATRIAL-NATRIURETIC-FACTOR (ANF)-LIKE IMMUNOREACTIVITY AND SECRETORY GRANULES IN INTERNAL GILLS TADPOLES OF SOUTH-AMERICAN TOAD BUFO-ARENARUM (HENSEL)

In this study, an ultrastructural and immunohistochemical analysis was carried out on the presence of Atrial Natriuretic Factor-like substan ce in the internal gills of premetamorphic larval stages of the South American toad. The results of immunohistochemical study indicate that, at larval 27 and following stages, ANF-like immunoreactive cells are seen in internal gills. At electron-microscopy level ''secretory granu les'' similar to those ANF-immunoreactives granules of myoendocrine ce lls of the same species are seen only in clear cells of gill rakers. O ur results reveal the occurrence of ANF-like substance in Bufo arenaru m gills and may suggest that ''cardiac hormones'' might play a paracri ne and/or autocrine role in the water and electrolyte balance at inter nal gills level.