Structure-activity studies of vasoactive intestinal peptide (VIP): cyclic disulfide analogs.
Analogs of vasoactive intestinal peptide with cysteine residues incorporated at selected sites within the sequence were prepared by solid phase methods, oxidized to the corresponding cyclic disulfides and purified to homogeneity by preparative HPLC. The cyclic compounds were assayed as smooth muscle relaxants on isolated guinea pig trachea, as bronchodilators in vivo in guinea pigs, and for binding to VIP receptors in guinea pig lung membranes. Of the analogs prepared at the N-terminus, one compound, Ac-[D-Cys6,D-Cys11,Lys12,Nle17,Val26,Th r28]-VIP, was found to be a full agonist with slightly more than one tenth the potency of native VIP. Most other cyclic analogs in the N-terminal region were found to be inactive. A second analog, Ac-[Lys12,Cys17,Val26,Cys28]-VIP, was also found to be a full agonist with potency about one third that of native VIP. Furthermore, this compound was active as a bronchodilator in vivo in guinea pig, but with somewhat diminished potency as compared to native VIP. Strikingly, this cyclic compound was found to have significantly longer duration of action (> 40 min) when compared to an analogous acyclic compound (5 min). The conformational restrictions imposed by formation of the cyclic ring structures may have stabilized the molecule to degradation, thus enhancing the effective duration of action. Analysis of this series of cyclic analogs has also yielded information about the requirements for the receptor-active conformation of VIP.
Department of Peptide Research, Hoffmann-La Roche Inc., Nutley.
D R
DR
Bolin
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J
Cottrell
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R
Garippa
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O'Neill
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Simko
M
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O'Donnell
D000595:Amino Acid Sequence; D000818:Animals; D016084:Bronchoconstriction / Q000187:drug effects; D001993:Bronchodilator Agents / Q000494:pharmacology; D004220:Disulfides / Q000737:chemistry / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D008969:Molecular Sequence Data; D009126:Muscle Relaxation / Q000187:drug effects; D011964:Receptors, Gastrointestinal Hormone / Q000378:metabolism; D018005:Receptors, Vasoactive Intestinal Peptide; D013329:Structure-Activity Relationship; D014132:Trachea / Q000187:drug effects; D014660:Vasoactive Intestinal Peptide / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology
D001993:Bronchodilator Agents; D004220:Disulfides; D011964:Receptors, Gastrointestinal Hormone; D018005:Receptors, Vasoactive Intestinal Peptide; D014660:Vasoactive Intestinal Peptide