Abstract
Calcitonin gene-related peptide (CGRP), adrenomedullin (AM), and amylin are structurally related peptides mediating vasorelaxation in the coronary circulation possibly via CGRP receptors (subtypes 1 or 2). Functional CGRP1 receptors appear to consist of at least three different kinds of proteins: the calcitonin receptor-like receptor (CRLR), receptor-activity-modifying proteins (RAMPs) and the receptor component protein (RCP). No CGRP2 receptor has yet been cloned. Using reverse transcriptase - polymerase chain reaction, the presence of mRNA sequences encoding CRLR, RCP and RAMPs was demonstrated in human coronary arteries. Relaxant responses were studied on isolated segments of coronary arteries after precontraction with U46619 (9,11-dideoxy-11α,9α-epoxymethano-prostaglandin F2α). The human peptides αCGRP, AM, and amylin induced relaxation with mean pEC50 values of 8.6, 6.8, and 6.3 M, respectively. Preincubation with αCGRP8–37(10−7 –10−5 M) and a novel nonpeptide CGRP antagonist “Compound 1” (WO98/11128) (10−7–10−5 M) caused a dose-dependent rightward shift of the concentration-response curves for αCGRP with pA2 values of 7.0 and 7.1, respectively. Preincubation with αCGRP8–37 (10−6 M) and Compound 1 (10−6 M) caused significant rightward shift of the concentration-response curves for AM and amylin as well with pKB values between 6.6 and 7.5. Preincubation with AM22–52 had no antagonistic effect on the AM and amylin response, neither did diacetoamidomethyl cysteine CGRP cause any concentration dependent (10−11–10−6 M) dilatation. In conclusion, mRNA for the components forming CGRP1 and AM receptors was detected in the human left anterior descending coronary arteries. αCGRP, AM, and amylin mediated vasorelaxation via the CGRP1 receptor. Compound 1 acted as a nonpeptide antagonist at the CGRP1 receptor and could thus become a tool for the study of CGRP-mediated functional responses in human tissue.
Footnotes
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The study was supported by the following foundations: The Danish Heart Foundation, Grant 99-1-2-19-22679; The Danish Hospital Foundation for Medical Research; Novo Nordisk Research Foundation; The Danish Medical Association Research Fund, and Fonden til Lægevidenskabens fremme, A.P. Møller og Hustru Chastine Mc-Kinney Møllers Fond til almene formaal.
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DOI: 10.1124/jpet.102.037754
- Abbreviations:
- CGRP
- calcitonin gene-related peptide
- AM
- adrenomedullin
- CRLR
- calcitonin receptor-like receptor
- [Cys(ACM)2,7]
- diacetoamidomethyl cysteine
- RAMP
- receptor-activity-modifying protein
- RCP
- receptor component protein
- U46619
- (9,11-dideoxy-11α,9α-epoxymethano-prostaglandin F2α)
- Compound 1 (WO 98/11128)
- (4-(2-oxo-2,3-dihydro-benzoimidazol-1-yl)-piperidine-1-carboxylic acid [1–3,5-dibromo-4-hydroxy-benzyl)-2-oxo-2-(4-phenyl-piperazin-1-yl)-ethyl]-amide
- LAD
- left anterior descending coronary artery
- RT-PCR
- reverse transcriptase-polymerase chain reaction
- bp
- base pair(s)
- Received April 22, 2002.
- Accepted September 26, 2002.
- The American Society for Pharmacology and Experimental Therapeutics
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