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

Abstract

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. 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. 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. 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.

Experiments on the mechanism of action of caerulein at the level of the guinea-pig ileum and colon

“…Caerulein (I) is a decapeptide present in the skin of Hyla caerulea and other Australian hylid frogs [1,2], ofLeptodactylus pentadactylus labyrinthicus and related South American leptodactylid frogs, and of the South African amphibian Xenopus laevis [3]. The amino acid sequences reported below clearly show the striking resemblance in chemical structure existing between the caeruleins, the C-terminal ectapeptide of porcine cholecystokininpancreozymin (II) and the Cterminal hexapeptide of gastrin II 0II).…”

Caerulein secretion by dermal glands in xenopus laevis

“…Anastasi et al (I) described the isolation of a decapeptide, caerulein, from extracts of the skin of the Australian tree frog, Hyla caerulea, and subsequently, caerulein was found in extracts of the skin of other species of amphibia including X. laevis (2). There are remarkable similarities in structure between the C-terminal portions of caerulein and the two mammalian hormones gastrin and cholecystokinin (CCK).…”

Venom evolution through gene duplications

“…Both have hormonal effects that induce the release of digestive enzymes causing muscle contractions. In vivo studies of amphibian ceruleins show a drop in blood pressure, contraction of the gall bladder and release of digestive secretions (Anastasi et al, 1970). Although phylogenetic analysis shows that the cerulein-like genes from Xenopus and Litoria are paralogous, and not orthologous, to each other, three residues from the mature peptides of the cerulein-like genes have converged through positive selection, suggesting that these specific residues may be advantageous in toxin function (Roelants et al, 2010).…”