Morphogenesis of the pancreas of Bufo bufo during metamorphosis.

Histology and immunohistochemical reactivity (IR) toward insulin, glucagon, somatostatin14, and pancreatic polypeptide were investigated in the pancreas and in other tissues of Bufo bufo during metamorphosis. Insulin IR cells appeared at the very beginning of metamorphosis among exocrine pancreatic cells rich in yolk platelets, not completely arranged in acini. Less than 1 week later, glucagon, somatostatin14, and pancreatic polypeptide IR cells also appeared. At metamorphic climax, both endocrine and exocrine tissues of the pancreas underwent extensive degeneration, mainly via apoptotic cellular death. At this time the number of IR cells and the intensity of immunohistochemical reactions decreased for all the hormones tested. Pancreatic reorganization began at the end of the climax.