title: G-protein βγ subunits in vasorelaxing and anti-endothelinergic effects of calcitonin gene-related peptide.
abstract: OBJECTIVE
  Calcitonin gene-related peptide (CGRP) has been proposed to relax vascular smooth muscle cells (VSMC) via cAMP and can promote dissociation of endothelin-1 (ET-1) from ET(A) receptors. The latter is not mimicked by other stimuli of adenylate cyclases. Therefore, we evaluated the involvement of G-protein βγ subunits (Gβγ) in the arterial effects of CGRP receptor stimulation.
  
  
  METHODS
  To test the hypothesis that instead of α subunits of G-proteins (Gαs), Gβγ mediates the effects of CGRP receptor activation, we used (i) rat isolated mesenteric resistance arteries (MRA), (ii) pharmacological modulators of cyclic nucleotides; and (iii) low molecular weight inhibitors of the functions of Gβγ, gallein and M119. To validate these tools with respect to CGRP receptor function, we performed organ bath studies with rat isolated MRA, radioligand binding on membranes from CHO cells expressing human CGRP receptors and cAMP production assays in rat cultured VSMC.
  
  
  RESULTS
  In isolated arteries contracted with K(+) or ET-1, IBMX (PDE inhibitor) increased sodium nitroprusside (SNP)- and isoprenaline (ISO)- but not CGRP-induced relaxations. While fluorescein (negative control) was without effects, gallein increased binding of [(125) I]-CGRP in the absence and presence of GTPγS. Gallein also increased CGRP-induced cAMP production in VSMC. Despite these stimulating effects, gallein and M119 selectively inhibited the relaxing and anti-endothelinergic effects of CGRP in isolated arteries while not altering contractile responses to K(+) or ET-1 or relaxing responses to ISO or SNP.
  
  
  CONCLUSIONS
  Activated CGRP receptors induce cyclic nucleotide-independent relaxation of VSMC and terminate arterial effects of ET-1 via Gβγ.
authors.affiliation: Department of Pharmacology, Maastricht University, Maastricht, the Netherlands.
authors.forename: M J P M T
authors.initials: MJ
authors.lastname: Meens
authors.forename: N J A
authors.initials: NJ
authors.lastname: Mattheij
authors.forename: P B
authors.initials: PB
authors.lastname: van Loenen
authors.forename: L J A
authors.initials: LJ
authors.lastname: Spijkers
authors.forename: P
authors.initials: P
authors.lastname: Lemkens
authors.forename: J
authors.initials: J
authors.lastname: Nelissen
authors.forename: M G
authors.initials: MG
authors.lastname: Compeer
authors.forename: A E
authors.initials: AE
authors.lastname: Alewijnse
authors.forename: J G R
authors.initials: JG
authors.lastname: De Mey
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D016466:CHO Cells; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism* / Q000494:pharmacology; D006224:Cricetinae; D003412:Cricetulus; D000242:Cyclic AMP / Q000378:metabolism; D003510:Cyclohexanes / Q000494:pharmacology; D044387:GTP-Binding Protein beta Subunits / Q000378:metabolism*; D044388:GTP-Binding Protein gamma Subunits / Q000378:metabolism*; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009599:Nitroprusside / Q000494:pharmacology; D051381:Rats; D011921:Rats, Inbred WKY; D018015:Receptors, Calcitonin Gene-Related Peptide / Q000378:metabolism*; D014664:Vasodilation / Q000187:drug effects; D014966:Xanthenes / Q000494:pharmacology
chemical_list: D003510:Cyclohexanes; C118981:G-protein Beta gamma; D044387:GTP-Binding Protein beta Subunits; D044388:GTP-Binding Protein gamma Subunits; C509953:M119 compound; D018015:Receptors, Calcitonin Gene-Related Peptide; D014966:Xanthenes; D009599:Nitroprusside; C007820:gallein; D000242:Cyclic AMP; D015740:Calcitonin Gene-Related Peptide; D007545:Isoproterenol; D015056:1-Methyl-3-isobutylxanthine
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