Structure-function studies on gastrointestinal hormones: I. Synthesis of secretin analogs and their biological and immunological properties

Abstract Syntheses by conventional procedures of the three analogs corresponding to the porcine secretin sequence crossed at position 6 by the N-terminal hexapeptide sequences of VIP, GIP, and glucagon are described, viz., Ala 4 ,Val 5 -, Tyr 1 ,Ala 2 ,Glu 3 -, and Gln 3 -secretin (VIP-SN, GIP-SN, and GLU-SN). The analog Phe 1 ,Phe 2 ,Trp 3 ,Lys 4 -secretin (SOMA-SN), designed on the basis of the surprising homology of the sequence portions 10–13 of somatostatin and 5–8 of secretin, was also prepared. Finally, the synthesis of N α -3-(4-hydroxyphenyl)propionyl-β-alanyl-secretin (DATA-SN), a tracer suitable for secretin radioimmunoassay and as an N-terminus modified secretin analog, is reported. The analogs are compared, in terms of their biological and immunological properties in different assay systems, with pure synthetic secretin.