Tha Na/Ca exchanger is active and working in the reverse mode in human umbilical artery smooth muscle cells

REBOLLEDO A.; SPERONI F.; RAINGO J; SALEMME S.V.; TANZI F; MUNIN V; AÑÓN M.C.; MILESI V

BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS

Año: 2006 vol. 339 p. 840 - 845

0006-291X

  AbstractThe data presented in this work suggest that in human umbilical artery (HUA) smooth muscle cells, the Na+/Ca2+ exchanger (NCX) is active and working in the reverse mode. This supposition is based on the following results: (i) micro.uorimetry in HUA smooth musclecells in situ showed that a Ca2+-free extracellular solution diminished intracellular Ca2+ ([Ca2+]i), and KB-R7943 (5 lM), a speci.c inhibitor of the Ca2+ entry mode of the exchanger, also decreased [Ca2+]i (40.6 ± 4.5% of Ca2+-free e.ect); (ii) KB-R7943 produced the relaxationof HUA rings (_24.7 ± 7.3 gF/gW, n = 8, p < 0.05); (iii) stimulation of the NCX by lowering extracellular Na+ increases basal [Ca2+]i proportionally to Na+ reduction (D .uorescence ratio = 0.593 ± 0.141 for Na+-free solution, n = 8) and HUA rings_ contraction (peak force = 181.5 ± 39.7 for 130 mM reduction, n = 8), both inhibited by KB-R7943 and a Ca2+-free extracellular solution. In conclusion, the NCX represents an important Ca2+ entry route in HUA smooth muscle cells.