The Na+/Ca2+ exchanger is active and working in the reverse mode in human umbilical artery smooth muscle cells |
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Authors: | Rebolledo A Speroni F Raingo J Salemme S V Tanzi F Munin V Añón M C Milesi V |
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Institution: | 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 |
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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. |
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Keywords: | Na+/Ca2+ exchanger Human umbilical artery Intracellular Ca2+ measurements KB-R7943 Low Na+-induced contractions |
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