title: HCO3-dependent impact of Na+,K+,2Cl- cotransport in vascular smooth muscle excitation-contraction coupling.
abstract: In smooth muscles, inhibition of Na(+),K(+),2Cl(-) cotransport (NKCC) by bumetanide decreased intracellular Cl(-) content ([Cl(-)](i)) and suppressed the contractions triggered by diverse stimuli. This study examines whether or not bicarbonate, a regulator of several Cl(-) transporters, affects the impact of NKCC in excitation-contraction coupling. Addition of 25 mM NaHCO(3) attenuated the inhibitory action of bumetanide on mesenteric artery contractions evoked by 30 mM KCl and phenylephrine (PE) by 5 and 3-fold, respectively. In cultured vascular smooth muscle cells, NaHCO(3) almost completely abolished inhibitory actions of bumetanide on transient depolarization and [Ca(2+)](i) elevation triggered by PE. In bicarbonate-free medium, bumetanide decreased [Cl(-)](i) by approximately 15%; this effect was almost totally abrogated by NaHCO(3). The addition of NaHCO(3) resulted in 2-fold inhibition of NKCC activity and 3-fold attenuation of [Cl(-)](i). These data strongly suggest that extracellular HCO(3)(-) diminishes the NKCC-sensitive component of excitation-contraction coupling via suppression of this carrier.
authors.affiliation: Research Centre, Centre hospitalier de l'Université de Montréal - Technopôle Angus, Montreal, Canada.
authors.forename: Svetlana V
authors.initials: SV
authors.lastname: Koltsova
authors.forename: Oksana G
authors.initials: OG
authors.lastname: Luneva
authors.forename: Julie L
authors.initials: JL
authors.lastname: Lavoie
authors.forename: Johanne
authors.initials: J
authors.lastname: Tremblay
authors.forename: Georgy V
authors.initials: GV
authors.lastname: Maksimov
authors.forename: Pavel
authors.initials: P
authors.lastname: Hamet
authors.forename: Sergei N
authors.initials: SN
authors.lastname: Orlov
mesh_terms: D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology*; D002034:Bumetanide / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D010656:Phenylephrine / Q000494:pharmacology; D028021:Sodium-Potassium-Chloride Symporters / Q000378:metabolism*
chemical_list: D001639:Bicarbonates; D028021:Sodium-Potassium-Chloride Symporters; D002034:Bumetanide; D010656:Phenylephrine