Synthesis of phenolic group containing analogues of porcine secretin and their immunological properties.

Syntheses by the conventional method are described of Nalpha-tyrosylsecretin, [Tyr1]secretin, and Nalpha-beta-(4-hydroxyphenyl)propionylsecretin. Secretin and [Tyr6]secretin were also prepared by the synthetic route identical with those employed for construction of the above analogues. Purification of secretin and the analogues was conducted by ion-exchange column chromatography on CM-Sephadex and gel filtration. Immunological reactivities of these analogues were examined in the radioimmunoassay system for secretin using two different antisera raised against synthetic secretin in rabbits. The tracers used in this study were [125I]-[Tyr1]secretin and [125I]-[Tyr6]secretin. The dose-response curves of Nalpha-tyrosylsecretin, [Tyr1]secretin, and Nalpha-beta-(4-hydroxphenyl)propionylsecretion were essentially superimposable upon those of natural and synthetic preparations of porcine secretin in the systems used, while [Tyr6]secretin showed discrepancy in the curve. In addition, biological activities of the synthetic polypeptides were compared with that of natural porcine secretin in term of exocrine pancreatic secretory response in anesthetized dogs.