Isolation and characterization of hypothalamic growth-hormone releasing factor from common carp, Cyprinus carpio

A growth hormone-releasing factor (GRF)-like peptide was isolated from the hypothalamus of common carp, Cyprinus carpio, by acid extraction, gel filtration chromatography, immunoaffinity chromatography using antiserum directed against rat GRF, and multiple steps of HPLC using octadecyl columns. Based on Edman degradation and peptide mapping, this teleost GRF was established to be a 45-residue peptide with the following primary structure: His-Ala-Asp-Gly-Met-Phe-Asn-Lys-Ala-Tyr-Arg-Lys-Ala-Leu-Gly-Gln-Leu-Ser- Ala-Arg - Lys-Tyr-Leu-His-Thr-Leu-Met-Ala-Lys-Arg-Val-Gly-Gly-Gly-Ser-Met-Ile-Glu- Asp-Asp-Asn-Glu-Pro-Leu-Ser. Carp GRF is closely related structurally to peptides of the glucagon-secretin superfamily, and more particularly to mammalian vasoactive intestinal peptide (VIP) precursors and the N-terminal portion of mammalian GRFs. A synthetic replicate of this peptide is highly potent [50% effective dose (ED50) approximately 0.08 nM] in stimulating GH release from cultured goldfish pituitary glands and in elevating serum GH levels 30 min after injection (0.1 micrograms/g) in goldfish.