Amphibian Bombesin-Like Peptides

The bombesin-like peptides are one of the classic examples of peptides first discovered in frog skin and then later found to be widely distributed in mammals. The prototypical bombesin-like peptide, bombesin was isolated from the skin of the frog Bombina bombin. In frogs, four groupings of bombesin-like peptides have been described: the bombesins, the ranatensins, and the phyllolitorins, which are present in skin, and gastrin-releasing peptide (GRP), which is not present in skin. The receptors for amphibian bombesin-like peptides are 7-transmembrane G-protein coupled receptors linked to generation of IPS. Different genuses of frogs contain different, characteristic, bombesin-like peptides. In frog skin the bombesin-like peptides are located in cutaneous granular glands. These are myoepithelial glands under adrenergic regulation such that subcutaneous injection of norepinephrine causes massive secretion of the contents of the glands. Bombesin-like peptides also function as neurotransmitters in frog brain. The localization and function of GRP in stomach suggests that amphibian GRP likely has similar functions in the GI tract of frogs as mammalian GRP does in mammals.