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Biomedical subjects

C F Hayward

Publications and source records attributed to C F Hayward.

10 recordsLinked to original sources
PubMed1990

Antagonists of bombesin/gastrin releasing peptide based on [D-Ala24]GRP(20-26)-heptapeptide. Modifications leading to potent analogues with prolonged duration of action.

Analogues of gastrin releasing peptide (GRP) and bombesin based on His-Trp-Ala-Val-D-Ala-His-Leu, the 20-26 heptapeptide sequence of [D-Ala24]GRP, have been synthesized and tested in vitro for their ability to inhibit GRP (18-27)-induced mitogenesis in Swiss 3T3 cells. Compounds identified as potent antagonists in this test system were also tested in vivo for their ability to inhibit bombesin-induced amylase secretion in rats. The Trp-Ala-Val sequence was found to be a very important feature of the antagonist activity; most substitutions in this region led either to much less potent or inactive analogues. In contrast, amino acid replacements in other parts of the molecule were more tolerated and sometimes led to marked increases in the in vitro and in vivo activity. The most potent analogues were obtained by replacing Leu26 by MeLeu and His25 by Lys(X) where X = Z, PhCO, PhCH2CO or Ph(CH2)2CO. Thus 4-pyridylcarbonyl-His-Trp-Ala-Val-D-Ala-Lys(CO-CH2-CH2-Ph)-Leu- NHMe (86) and 4-pyridylcarbonyl-His-Trp-Ala-Val-D-Ala-Lys(Z)-MeLeu-OMe (87) had IC50 values of less than 20 micrograms/kg s.c. in vivo, and their effects lasted for more than 3 hr.

Amino Acid Sequence↗
PubMed1989

N-isobutyryl-His-Trp-Ala-Val-D-Ala-His-Leu-NHMe (ICI 216140) a potent in vivo antaconist analogue of bombesin/gastrin releasing peptide (BN/GRP) derived from the C-terminal sequence lacking the final methionine residue.

The GRP receptor mediated growth response in Swiss 3T3 cells has been used to identify BN/GRP antagonists. Analysis of bombesin antagonism by substance P analogues and by truncated GRP analogues revealed that deletion of the C-terminal methionine residue was important for antagonism. Des-Met analogues showing potent antagonist activity in the in vitro 3T3 system (IC50 approximately 2nM) were synthesized. Further structural modification of these peptides led to the identification of (CH3)2CHCO-His-Trp-Ala-Val-D-Ala-His-Leu-NHCH3 (ICI 216140) which reduced bombesin-stimulated rat pancreatic amylase secretion to basal levels when administered subcutaneously at 2.0 mg per kg.

Amino Acid Sequence↗
PubMed1986

New delta-receptor antagonists.

A new delta-selective opiate antagonist has been synthesised in which the two glycine residues of diallyl leucine enkephalin have been replaced by 4-aminobenzoic acid. The compound has a different conformation to that of ICI 174,864 (N,N-diallyl-Tyr-Aib-Aib-Phe-Leu).

Animals↗
PubMed1986

Dimeric opioid antagonists.

Symmetrical and unsymmetrical dimeric pentapeptide opioid antagonists have been prepared and studied on the mouse vas deferens preparation. The findings do not support the hypothesis that such agents bind to dimeric delta-opioid receptors.

Animals↗
PubMed1980

Non-reducible cyclic, and azaphenylalanyl6 analogues of somatostatin.

SSeven new analogues of somatostatin are described, along with the effects of these analogues on pentagastrin-stimulated gastric acid and pepsin secretion in conscious cats. Replacement of the cystine disulphide bridge of somatostatin with an amide bridge, with or without deletion of the N-terminal dipeptide, resulted in analogues with approximately 20% of the potency of somatostatin. Simultaneous ommision of Lys4 in the amide-bridge analogues reduced the activity of the peptides to approximately 5% of somatostatin. Substitution of Phe6 of somatostatin or an amide-bridged analogue with azaphenylalanyl resulted in peptides with no detectable activity. The results illustrate the possible importance of the basic side-chain of Lys4 for the activity of somatostatin. The lack of activity of azaphenylalanyl6 analogues of somatostatin demonstrate the extreme importance of the orientation of the side-chain of Phe6 for the activity of somatostatin, possibly for the binding to somatostatin receptors.

Amino Acid Sequence↗