title: Na(+)-independent Mg(2+) transport sensitive to 2-aminoethoxydiphenyl borate (2-APB) in vascular smooth muscle cells: involvement of TRPM-like channels.
abstract: Magnesium is associated with several important cardiovascular diseases. There is an accumulating body of evidence verifying the important roles of Mg(2+)-permeable channels. In the present study, we estimated the intracellular free Mg(2+) concentration ([Mg(2+)](i)) using (31)P-nuclear magnetic resonance ((31)P-NMR) in porcine carotid arteries. pH(i) and intracellular phosphorus compounds were simultaneously monitored. Removal of extracellular divalent cations (Ca(2+) and Mg(2+)) in the absence of Na(+) caused a gradual decrease in [Mg(2+)](i) to approximately 60% of the control value after 125 min. On the other hand, the simultaneous removal of extracellular Ca(2+) and Na(+) in the presence of Mg(2+) gradually increased [Mg(2+)](i) in an extracellular Mg(2+)-dependent manner. 2-aminoethoxydiphenyl borate (2-APB) attenuated both [Mg(2+)](i) load and depletion caused under Na(+)- and Ca(2+)-free conditions. Neither [ATP](i) nor pH(i) correlated with changes in [Mg(2+)](i). RT-PCR detected transcripts of both TRPM6 and TRPM7, although TRPM7 was predominant. In conclusion, the results suggest the presence of Mg(2+)-permeable channels of TRPM family that contribute to Mg(2+) homeostasis in vascular smooth muscle cells. The low, basal [Mg(2+)](i) level in vascular smooth muscle cells is attributable to the relatively low activity of this Mg(2+) entry pathway.
authors.affiliation: Department of Cardiology, Nagoya University Graduate School of Medicine, Nagoya, Japan.
authors.forename: Yukihisa
authors.initials: Y
authors.lastname: Hamaguchi
authors.forename: Tatsuaki
authors.initials: T
authors.lastname: Matsubara
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Amano
authors.forename: Tadayuki
authors.initials: T
authors.lastname: Uetani
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Asano
authors.forename: Takashi
authors.initials: T
authors.lastname: Iwamoto
authors.forename: Koichi
authors.initials: K
authors.lastname: Furukawa
authors.forename: Toyoaki
authors.initials: T
authors.lastname: Murohara
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Nakayama
mesh_terms: D000818:Animals; D001692:Biological Transport; D001896:Boron Compounds / Q000494:pharmacology; D002339:Carotid Arteries / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D019906:Nuclear Magnetic Resonance, Biomolecular; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012964:Sodium / Q000378:metabolism*; D013552:Swine; D050053:TRPM Cation Channels / Q000235:genetics / Q000502:physiology*
chemical_list: D001896:Boron Compounds; D050053:TRPM Cation Channels; D012964:Sodium; C109986:2-aminoethoxydiphenyl borate; D008274:Magnesium