Purification of dog VIP from a single animal.

VIP, a potent vasodilator peptide, is reported to be identical in pig, cow, human and rat but to differ in four amino acids in chicken. This report describes the purification of dog VIP from the small intestine of a single animal. The purification method is based on tissue extraction with a sequence of organic solvents. The extracted VIP is concentrated onto cation-exchange cellulose and brought to purity by three HPLC steps. A 30% final yield of pure VIP was obtained from the original extract. Dog VIP was found to have the following sequence: His-Ser-Asp-Ala-Val-Phe-Thr-Asp-Asn-Tyr-Thr-Arg-Leu-Arg-Lys-Gln-Met-Ala -Val-Lys-Lys-Tyr-Leu-Asn-Ser-Ile-Leu-Asn. Thus the amino acid sequence of dog VIP is identical with all the mammalian VIP's which have been reported. This suggests that a high degree of conservation throughout the molecule may be required for VIP bioactivity.