Dermorphin and related peptides in rat tissues.

Dermorphin (Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2), a naturally occurring peptide isolated from arboreal frog skin, is endowed with outstanding structural and biological features. It has no structural community with the sequence of mammalian opioid peptides and is a unique example of a D-aminoacid containing peptide which is synthesized via ribosomal route. Dermorphin is the most potent of the opioid peptides or opiates in producing long lasting analgesia and catalepsy. Since most amphibians' secretory peptides have counterparts in the mammalian central nervous system and gastrointestinal tract, we have developed a sensitive enzyme immunoassay that can detect 1 pg dermorphin to verify the possibility of dermorphin or dermorphin-related peptides occurrence in mammalian tissues. Dermorphin-related peptides were purified by fast protein liquid chromatography followed by reverse phase high pressure liquid chromatography. Identification was achieved by chromatographic comparison with synthetic standards and immunological analysis. A peptide behaving like authentic dermorphin was detected (2 ng/g) in rat small intestine. Immunoreactive species of higher Mr were also detected in the brain, adrenal glands and gastrointestinal tract, they may represent extended forms of dermorphin or homologous peptides.