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

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Abstract
1 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 μg/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.