dermorphin--4-hyp(6)- and dermorphin

Dermorphin and its Hyp6 analogue are opiate-like heptapeptides originally discovered in frog skin and characterized by the presence of a D-Ala2 residue in their sequence. They were assayed for their capacity to compete with [3H]Leu-enkephalin for binding to opioid receptors in membranes of neuroblastoma x glioma hybrid cells. In the presence of 7 nM-[3H]Leu-enkephalin, the concentrations at which they caused 50% inhibition of [3H]enkephalin binding (IC50 values) are 0.1 micro M and 0.3 micro M, respectively. In contrast, the synthetic L-Ala2-dermorphin shows very low affinity for the opioid receptors. In addition, like other opioid peptides, dermorphin and hyp6-dermorphin inhibit the elevation by prostaglandin E1 (PGE1) of the level of adenosine 3':5'-cyclic monophosphate (cyclic AMP) (IC50 values 0.2 micro M and 0.4 micro M, respectively). The inhibition is prevented by the opiate antagonist naloxone, L-Ala2-dermorphin is at least three orders of magnitude less potent in inhibiting the PGE1-evoked increase in the level of cyclic AMP. The results show that peptides with an amino acid sequence quite different from that of the enkephalins can bind to opioid receptors of the hybrid cells.

Topics: Amphibians; Animals; Binding, Competitive; Cell Line; Enkephalin, Leucine; Enkephalins; Glioma; Hybrid Cells; Kinetics; Mice; Neuroblastoma; Oligopeptides; Opioid Peptides; Rats; Receptors, Opioid; Structure-Activity Relationship

1 Dermorphin and Hyp6-dermorphin are the first representatives of a new class of potent opioid peptides occurring in amphibian skin. They present the unique feature of having a D-Ala residue incorporated in the peptide molecule. 2 Dermorphin displayed a potent depressive action on electrically stimulated contractions of the guinea-pig ileum and mouse vas deferens preparations. Dermorphin was respectively 57,294, 18 and 39 times more potent than Met-enkephalin, Leu-enkephalin, beta-endorphin, and morphine on the guinea-pig ileum opiate receptors. On the vas deferens receptors, dermorphin was about as potent as the enkephalins and 40 times more potent than morphine. Naloxone was a powerful antagonist to dermorphin in both preparations. 3 Dermorphin produced potent and long-lasting analgesia in mice by intravenous injection, and in rats by intracerebroventricular injection, the ED50 being here of the order of 13-23 pmol/rat. Morphine was 752 and 2170 times less potent, depending on the analgesia test used. At high intracerebroventricular doses analgesia was accompanied by catalepsy. 4 Intracerebroventricular infusion of dermorphin induced development of tolerance and precipitation of withdrawal symptoms upon administration of naloxone. Both tolerance and physical dependence was consistently less marked with dermorphin than with morphine. 5 The minimum sequence requirement for full dermorphin activity was represented by the N-terminal tetrapeptide. The presence of the D-Ala2-residue was of crucial importance.

Topics: Amphibians; Analgesics; Animals; Catalepsy; Drug Tolerance; Guinea Pigs; Humans; Ileum; In Vitro Techniques; Male; Mice; Narcotics; Oligopeptides; Opioid Peptides; Skin; Vas Deferens

H-Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2 (dermorphin) and H-Tyr-D-Ala-Phe-Gly-Tyr-Hyp-Ser-NH2 (Hyp6-dermorphin) are two members of a new class of opiate-like peptides present in the amphibian skin. Their syntheses and that of the L-Ala2-analogue of dermorphin have been accomplished by conventional segment condensation in solution.

Topics: Amino Acid Sequence; Animals; Anura; Methods; Narcotics; Oligopeptides; Opioid Peptides; Peptide Fragments

Histochemistry has been the springboard for the identification in molluscan tissues (hypobranchial body and salivary glands) and amphibian skin of a number of biogenic amines, choline esters and active peptides. Among the biogenic amines 5-HT and related indolealkylamines, octopamine, tyramine and several histamines are to be listed; among the choline esters murexine, dihydromurexine, senecioylcholine and acryloylcholine; among the peptides an array of compounds belonging to at least ten different peptide families. 5-HT, octopamine, tyramine and histamine are present, together with representatives of some peptide families in the posterior salivary glands of octopods, the hypobranchial body of prosobranchiate molluscs and the amphibian skin. This points to the possible occurrence in the above structures of cells belonging to the Pearse's APUD series, intended in its broadest sense. Immunocytochemical studies and even ultrastructural studies on amine and peptide storing cells in molluscan tissues and amphibian skin are virtually lacking. This is certainly a gap that deserves to be filled, considering that these studies may help in elucidating problems of general relevance in invertebrates and vertebrates.

Topics: Amphibian Proteins; Amphibians; Animals; Biogenic Amines; Chemical Phenomena; Chemistry; Gills; Histocytochemistry; Octopodiformes; Oligopeptides; Opioid Peptides; Peptide Hormones; Peptides; Salivary Glands; Skin

Methanol extracts of the skin of the Brazilian frog Phyllomedusa rhodei contain approximately equal amounts of dermorphin and its analogue Hyp6-dermorphin, two opiate-like heptapeptides. A unique feature of their sequence is the presence of a D-amino acid residue at position 2. Hyp6-dermorphin possesses a spectrum of central and peripheral bioactivity very similar to that of dermorphin.

Topics: Amino Acid Sequence; Amino Acids; Animals; Anura; Biological Assay; Endorphins; Hydroxyproline; Oligopeptides; Opioid Peptides; Proline; Skin