A peptide of the pancreatic polypeptide (PP) family was isolated in pure form from the pancreas of an elas- mobranch fish, Scyliorhinus canicula (European common dogfish). The primary structure of the peptide was established as: Tyr-Pro-Pro-Lys-Pro-Glu-Asn-Pro-Gly-Glu10-Asp-Ala-Pro- Pro-Glu-Glu-Leu-Ala-Lys-Tyr20-Tyr-Ser-Ala-Leu-Arg-His- Tyr-Ile-Asn-Leu30-Ile-Thr-Arg-Gln-Arg-Tyr · NH2. This sequence contains 86% amino acid sequence homology with human neuropeptide Y, and the COOH-terminal region (residues 2036) has been fully conserved. Bolus injection of a synthetic replicate of the peptide (0.5-4 nmol) into the celiac artery of conscious dogfish resulted in a significant (P < 0.01) and dose- dependent increase in arterial blood pressure. A maximum rise in mean pressure (67 ±11% over mean basal values; n = 6) was elicited by an injection of 2 nmol peptide. Bolus injections of human neuropeptide Y (0.5-4 nmol) also elicited dose-dependent rises in blood pressure, and the effects produced by the dogfish and human peptides were not significantly different at any dose. The data are consistent with a physiological role for neuropeptide Y-related peptide in cardiovascular regulation in elasmo- branch fish.
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