Muscarinic M3-receptors mediate cholinergic synergism of mitogenesis in airway smooth muscle.
Muscarinic receptor agonists have been considered to act synergistically in combination with growth facors on airway smooth muscle growth. Characterization of the proliferative responses and of the receptor subtype(s) involved has not yet been studied. Therefore, we investigated mitogenesis induced by stimulation of muscarinic receptors, alone and in combination with stimulation by platelet-derived growth factor (PDGF). For this purpose, [(3)H]thymidine-incorporation was measured at different culture stages in bovine tracheal smooth muscle cells. Functional muscarinic M(3)-receptors, as measured by formation of inositol phosphates, were present in unpassaged cells, but were lacking in passage 2 cells. Methacholine (10 microM) by itself was not able to induce a proliferative response in both cell culture stages. However, methacholine interacted synergistically with PDGF in a dose-dependent fashion (0.1-10 microM), but only in cells having functional muscarinic M(3)-receptors. This synergism could be suppressed significantly by the selective M(3)-receptor antagonists DAU 5884 (0.1 microM) and 4-DAMP (10 nM), but not at all by the M(2)-subtype selective antagonist gallamine (10 microM). These results show that methacholine potentiates mitogenesis induced by PDGF solely through stimulation of muscarinic M(3)-receptors in bovine tracheal smooth muscle cells.
Gosens
Reinoud
R
Department of Molecular Pharmacology, University Centre for Pharmacy, Groningen, The Netherlands. R.Gosens@farm.rug.nl
Nelemans
S Adriaan
SA
Grootte Bromhaar
Mechteld M
MM
McKay
Sue
S
Zaagsma
Johan
J
Meurs
Herman
H
D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D004357:Drug Synergism; D007295:Inositol Phosphates / Q000378:metabolism; D016210:Methacholine Chloride / Q000008:administration & dosage / Q000494:pharmacology; D008938:Mitosis / Q000187:drug effects; D018721:Muscarinic Agonists / Q000494:pharmacology; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010880:Piperidines / Q000494:pharmacology; D010982:Platelet-Derived Growth Factor / Q000008:administration & dosage / Q000494:pharmacology; D043587:Receptor, Muscarinic M3; D011976:Receptors, Muscarinic / Q000378:metabolism*; D013936:Thymidine / Q000378:metabolism; D014132:Trachea / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
D007295:Inositol Phosphates; D018721:Muscarinic Agonists; D018727:Muscarinic Antagonists; D010880:Piperidines; D010982:Platelet-Derived Growth Factor; D043587:Receptor, Muscarinic M3; D011976:Receptors, Muscarinic; D016210:Methacholine Chloride; C042375:4-diphenylacetoxy-1,1-dimethylpiperidinium; D013936:Thymidine