title: The Na+/Ca2+ exchanger is active and working in the reverse mode in human umbilical artery smooth muscle cells.
abstract: The data presented in this work suggest that in human umbilical artery (HUA) smooth muscle cells, the Na(+)/Ca(2+) exchanger (NCX) is active and working in the reverse mode. This supposition is based on the following results: (i) microfluorimetry in HUA smooth muscle cells in situ showed that a Ca(2+)-free extracellular solution diminished intracellular Ca(2+) ([Ca(2+)](i)), and KB-R7943 (5microM), a specific inhibitor of the Ca(2+) entry mode of the exchanger, also decreased [Ca(2+)](i) (40.6+/-4.5% of Ca(2+)-free effect); (ii) KB-R7943 produced the relaxation of HUA rings (-24.7+/-7.3gF/gW, n=8, p<0.05); (iii) stimulation of the NCX by lowering extracellular Na(+) increases basal [Ca(2+)](i) proportionally to Na(+) reduction (Delta fluorescence ratio=0.593+/-0.141 for Na(+)-free solution, n=8) and HUA rings' contraction (peak force=181.5+/-39.7 for 130mM reduction, n=8), both inhibited by KB-R7943 and a Ca(2+)-free extracellular solution. In conclusion, the NCX represents an important Ca(2+) entry route in HUA smooth muscle cells.
authors.affiliation: Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Calles 47 y 115, La Plata (1900), Argentina. ar@biol.unlp.edu.ar
authors.forename: A
authors.initials: A
authors.lastname: Rebolledo
authors.forename: F
authors.initials: F
authors.lastname: Speroni
authors.forename: J
authors.initials: J
authors.lastname: Raingo
authors.forename: S V
authors.initials: SV
authors.lastname: Salemme
authors.forename: F
authors.initials: F
authors.lastname: Tanzi
authors.forename: V
authors.initials: V
authors.lastname: Munin
authors.forename: M C
authors.initials: MC
authors.lastname: Añón
authors.forename: V
authors.initials: V
authors.lastname: Milesi
mesh_terms: D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D006801:Humans; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism* / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D014469:Umbilical Arteries / Q000187:drug effects / Q000201:enzymology*
chemical_list: D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium