title: Differential adrenomedullin release and endothelin receptor expression in distinct subpopulations of human airway smooth-muscle cells.
abstract: Although adrenomedullin (ADM) is implicated in the control of airway tone, regulation of ADM release from airway smooth-muscle cells (ASMCs) has not been explored. Preliminary experiments have indicated that human ASMC populations were heterogeneous in their rate of ADM release and expression of endothelin (ET)(A) and ET(B) receptors. We isolated these phenotypically distinct ASMCs from explants derived from the same airway segment. ASMCs possessing exclusively ET(A) receptors appeared smaller and proliferated faster than ET(A)/ET(B) isolates. Macroautoradiographic analysis confirmed the presence of both receptors in human bronchi. ADM release and messenger RNA expression was greater in ET(A)/ET(B) isolates compared with ET(A) isolates. No measurable ET release was detected from ASMCs. Exogenous ET-1 (1 to 100 nM) more potently stimulated the release of ADM from ET(A)/ET(B) compared with ET(A) isolates. In addition, ET-3 (1 to 100 nM) stimulated ADM release only from ET(A)/ET(B) isolates, implicating the ET(B) receptor in this response. Exogenous ET-1 potentiated platelet- derived growth factor-stimulated [3H]thymidine uptake in ET(A)/ ET(B) but not ET(A) isolates. ET-3 did not affect [3H]thymidine uptake in either cell type. Possession of ET(A)/ET(B) receptors is associated with higher rates of ADM release and slower proliferation, but a capacity for ET-1 stimulated DNA synthesis via ET(A) receptors. These results support a paracrine role for the regulation of ADM release predominantly via the ET(B) receptor in human ASMCs.
authors.affiliation: Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge, United Kingdom.
authors.forename: P D
authors.initials: PD
authors.lastname: Upton
authors.forename: J
authors.initials: J
authors.lastname: Wharton
authors.forename: N
authors.initials: N
authors.lastname: Davie
authors.forename: M A
authors.initials: MA
authors.lastname: Ghatei
authors.forename: D M
authors.initials: DM
authors.lastname: Smith
authors.forename: N W
authors.initials: NW
authors.lastname: Morrell
mesh_terms: D053607:Adrenomedullin; D001345:Autoradiography; D001980:Bronchi / Q000166:cytology / Q000378:metabolism*; D001993:Bronchodilator Agents / Q000378:metabolism; D048429:Cell Size; D002478:Cells, Cultured; D016232:Endothelins / Q000378:metabolism; D006801:Humans; D007457:Iodine Radioisotopes / Q000378:metabolism; D009130:Muscle, Smooth / Q000166:cytology / Q000378:metabolism*; D010455:Peptides / Q000235:genetics / Q000378:metabolism*; D020033:Protein Isoforms; D017466:Receptors, Endothelin / Q000235:genetics / Q000378:metabolism*
chemical_list: D001993:Bronchodilator Agents; D016232:Endothelins; D007457:Iodine Radioisotopes; D010455:Peptides; D020033:Protein Isoforms; D017466:Receptors, Endothelin; D053607:Adrenomedullin