Ultrastructural study of the endocrine pancreas of the toad Bufo arenarum

ABSTRACT

The aim of the present report was to identify by electron microscopy the different endocrine cell types of the toad pancreas. Thus, we studied the pancreas from male specimens of Bufo arenarum with routine techniques for transmission electron microscopy. The results showed the presence of four endocrine cells types which would correspond to those responsible for the different pancreatic hormonal secretions in other species (B, A, D and PP cells). Type 1 cells contained rounded secretory granules with a clear halo which responded to two varieties a) measuring 200 to 400 mm, and b) having a crystalloid core and a diameter of 400 to 600 nm; these cells would correspond to B cells showed rounded or irregular granules of 104 to 400 nm; they would be equivalent to A cells. Type 3 cells presented polymorphic ganules, most of them peanut-shaped, measuring 115 to 850 nm; they would resemble D cells. Finally, Type 4 cells contained rounded granules of 80 to 400 nm; these cells would correspond to PP cells. In addition, we also observed mixed cells exhibiting similar characteristics to acinar cells, but containing secretory granules resembling those found in some of the endocrine cell types; these would correspond to the acinar-islet cells reported in other animals. In conclusion, we described the ultrastructure of the toad endocrine pancreas and compare it with previous observations made in other amphibians.