Presence of caerulein in extracts of the skin of Leptodactylus pentadactylus labyrinthicus and of Xenopus laevis

The South American amphibian Leptodactylus pentadactylus labyrinthicus and the South African amphibian Xenopus laevis contain in their skin a polypeptide indistinguishable from caerulein prepared from the Australian amphibian Hyla caerulea.2. The caerulein content of different batches of Leptodactylus pentadactylus labyrinthicus skins varies from 10 to 500-600 mug/g tissue. Drying of the skin causes either a moderate decrease or a slight increase in the caerulein content. Methanol extraction gives considerably higher yields of caerulein than acetone extraction.3. Caerulein or caerulein-like polypeptides also occur in the skin of several other species of Leptodactylus together with 5-hydroxyindole alkylamines and imidazole alkylamines. Yet other species of Leptodactylus lack caerulein-like polypeptides and 5-hydroxyindole alkylamines.4. It is suggested that caerulein and caerulein-like polypeptides may have some function either in the regulation of secretory processes of the skin or in the exchange of water and electrolytes through the skin, or in both.