[D-Phe12]-Bombesin

Conformation studies on bombesin receptor antagonists: 500 MHz NMR and CD characterization of synthetic (D-Phe12, Leu14)-bombesin.[Pubmed:2545203]

Biochem Biophys Res Commun. 1989 Jun 30;161(3):987-93.

The conformation flexibility of the tetradecapeptide hormone bombesin and its synthetic antagonist (DPhe12, Leu14)-bombesin has been studied using nuclear magnetic resonance and circular dichroism techniques. The spectral features observed indicate that the ordered structure present in the C-terminal pentapeptide moiety of native BBS is lost in the (DPhe12, Leu14) analog.

[D-Phe12]bombesin analogues: a new class of bombesin receptor antagonists.[Pubmed:2435173]

Am J Physiol. 1987 Mar;252(3 Pt 1):G439-42.

Previous attempts to develop analogues of bombesin that function as specific receptor antagonists have been unsuccessful. Alteration of the histidine in luteinizing hormone releasing factor has resulted in analogues that function as competitive antagonists. In the present study we have used a similar strategy and altered the histidine in bombesin. [D-Phe12]bombesin, [D-Phe12,Leu14]bombesin, and [Tyr4,D-Phe12]bombesin did not stimulate amylase release from guinea pig pancreatic acini when present alone, but each analogue inhibited bombesin-stimulated secretion. For each analogue, detectable inhibition occurred at 1 microM and half-maximal inhibition at 4 microM. Each analogue inhibited amylase release by bombesin and other agonists that stimulate secretion by interacting with bombesin receptors. The analogues of bombesin did not alter stimulation by substance P or other agonists that interact with other receptors. The inhibition of the action of bombesin was competitive with Schild plots having slopes of 1.0. Each analogue also inhibited binding of 125I-labeled [Tyr4]bombesin but not 125I-labeled substance P. These results demonstrate that [D-Phe12] analogues of bombesin function as bombesin receptor antagonists and are the only bombesin receptor antagonists that interact only with the bombesin receptor. Because of their specificity, these analogues may prove useful for defining the role of bombesin in various physiological or pathological processes.

(D-Phe12) bombesin and substance P analogues function as central bombesin receptor antagonists.[Pubmed:2463692]

Synapse. 1988;2(3):282-7.

The potency of synthetic bombesin (BN) analogues with D-Phe12 substitutions and substance P analogues was investigated in the rat CNS. (D-Phe12,Leu14)BN, (D-Phe12)BN and (Tyr4,D-Phe12)BN inhibited binding to rat brain slices with IC50 values of approximately 2 microM. Similarly, spantide inhibited binding to rat brain slices with an IC50 value of 1.5 microM. Spantide inhibited specific (125I-Tyr4)BN binding as a result of decreased rate of association, whereas the rate of dissociation was unaffected. Neither the (D-Phe12)BN analogues nor the substance P analogues inhibited specific binding of 125I-VIP to rat brain slices. Central administration of BN (0.5 micrograms) induced grooming and suppressed feeding and resting. (Tyr4, D-Phe12)BN (5 micrograms) antagonized the behavioral effects of BN. Although spantide (2 micrograms) also antagonized many of the BN effects, it had intrinsic effects and hence the behavioral antagonism was not specific. These data suggest that although both (D-Phe12)BN and substance P analogues may function as central BN receptor antagonists, the (D-Phe12)BN analogues may be functionally the more useful class of antagonists.

Localization of receptors for bombesin-like peptides in the rat brain.[Pubmed:2853589]

Ann N Y Acad Sci. 1988;547:114-30.

BN-like peptides and receptors are present in discrete areas of the mammalian brain. By radioimmunoassay, endogenous BN/GRP, neuromedin B, and ranatensin-like peptides are present in the rat brain. High-to-moderate concentrations of BN/GRP are present in the rat hypothalamus and thalamus, whereas moderate-to-high densities of neuromedin B and ranatensin-like peptides are present in the olfactory bulb and hippocampus, as well as in the hypothalamus and thalamus. While the distribution of neuromedin B and ranatensin-like peptides appears similar, it is distinct from that of BN/GRP. When released from CNS neurons, these peptides may interact with receptors for BN-like peptides. BN, GRP, ranatensin, and neuromedin B inhibit specific [125I-Tyr4]BN binding with high affinity. By use of in vitro autoradiographic techniques to detect binding of [125I-Tyr4]BN to receptors for BN-like peptides, high grain densities were found in the olfactory bulb and tubercle, the nucleus accumbens, the suprachiasmatic and paraventricular nucleus of the hypothalamus, the central medial and paraventricular thalamic nuclei, the hippocampus, the dentate gyrus, and the amygdala of the rat brain. Some of these receptors may be biologically active and mediate the biological effects of BN-like peptides. For example, when BN is directly injected into the nucleus accumbens, pronounced grooming results and the effects caused by BN are reversed by spantide and [D-Phe12]BN. Thus, the putative BN receptor antagonists may serve as useful agents to investigate the biological significance of BN-like peptides in the CNS.