Characterization of receptors for calcitonin gene-related peptide and adrenomedullin on the guinea-pig vas deferens.
1. The receptors which mediate the effects of calcitonin gene-related peptide (CGRP), amylin and adrenomedullin on the guinea-pig vas deferens have been investigated. 2. All three peptides cause concentration dependant inhibitions of the electrically stimulated twitch response (pD2s for CGRP, amylin and adrenomedullin of 7.90+/-0.11, 7.70+/-0.19 and 7.25+/-0.10 respectively). 3. CGRP8-37 (1 microM) and AC187 (10 microM) showed little antagonist activity against adrenomedullin. 4. Adrenomedullin22-52 by itself inhibited the electrically stimulated contractions of the vas deferens and also antagonized the responses to CGRP, amylin and adrenomedullin. 5. [125I]-adrenomedullin labelled a single population of binding sites in vas deferens membranes with a pIC50 of 8.91 and a capacity of 643 fmol mg(-1). Its selectivity profile was adrenomedullin> AC187>CGRP=amylin. It was clearly distinct from a site labelled by [125I]-CGRP (pIC50=8.73, capacity=114 fmol mg(-1), selectivity CGRP>amylin=AC187>adrenomedullin). [125I]-amylin bound to two sites with a total capacity of 882 fmol mg(-1). 6. Although CGRP has been shown to act at a CGRP2 receptor on the vas deferens with low sensitivity to CGRP8-37, this antagonist displaced [125I]-CGRP with high affinity from vas deferens membranes. This affinity was unaltered by increasing the temperature from 4 degrees C to 25 degrees C, suggesting the anomalous behaviour of CGRP8-37 is not due to temperature differences between binding and functional assays.
Poyner
D R
DR
Pharmaceutical Sciences Institute, Aston University, Birmingham, England. poynerdr@aston.ac.uk
Taylor
G M
GM
Tomlinson
A E
AE
Richardson
A G
AG
Smith
D M
DM
D053607:Adrenomedullin; D000682:Amyloid / Q000494:pharmacology; D000818:Animals; D001667:Binding, Competitive; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology; D006168:Guinea Pigs; D007457:Iodine Radioisotopes; D058228:Islet Amyloid Polypeptide; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D009119:Muscle Contraction / Q000187:drug effects; D010446:Peptide Fragments / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology; D011869:Radioligand Assay; D058265:Receptors, Adrenomedullin; D018015:Receptors, Calcitonin Gene-Related Peptide / Q000378:metabolism*; D018000:Receptors, Peptide; D014649:Vas Deferens / Q000187:drug effects / Q000378:metabolism*; D014665:Vasodilator Agents / Q000494:pharmacology
D000682:Amyloid; D007457:Iodine Radioisotopes; D058228:Islet Amyloid Polypeptide; D008565:Membrane Proteins; D010446:Peptide Fragments; D010455:Peptides; D058265:Receptors, Adrenomedullin; D018015:Receptors, Calcitonin Gene-Related Peptide; D018000:Receptors, Peptide; D014665:Vasodilator Agents; C058636:calcitonin gene-related peptide (8-37); D053607:Adrenomedullin; D015740:Calcitonin Gene-Related Peptide