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Na(+)-independent Mg(2+) transport sensitive to 2-aminoethoxydiphenyl borate (2-APB) in vascular smooth muscle cells: involvement of TRPM-like channels.

Hamaguchi Y, Matsubara T, Amano T, Uetani T, Asano H, Iwamoto T, Furukawa K, Murohara T, Nakayama S - J. Cell. Mol. Med. (2008)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Cardiology, Nagoya University Graduate School of Medicine, Nagoya, Japan.

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.

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Changes in [Mg2+]i (A) and pHi (B) during exposures to Ca2+- and Na+-free solutions containing Mg2+. After the carotid artery preparations were superfused with a Ca2+-free solution containing 1.2 mM Mg2+, extra-cellular Na+ was removed for 125 min (filled symbols: ▪, •). In the experiments indicated by open symbols (□, ○), extracellular Mg2+ was increased to 6.0 mM during Na+ removal. Asterisks indicate statistically significant differences compared to the [Mg2+]i and pHi values before removal of extracellular Mg2+ (*, P<0.05; **, P<0.01). Crosses on open symbols indicate statistically significant differences compared to the filled symbols at the same time point (†, P<0.05;††, P<0.01).
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fig04: Changes in [Mg2+]i (A) and pHi (B) during exposures to Ca2+- and Na+-free solutions containing Mg2+. After the carotid artery preparations were superfused with a Ca2+-free solution containing 1.2 mM Mg2+, extra-cellular Na+ was removed for 125 min (filled symbols: ▪, •). In the experiments indicated by open symbols (□, ○), extracellular Mg2+ was increased to 6.0 mM during Na+ removal. Asterisks indicate statistically significant differences compared to the [Mg2+]i and pHi values before removal of extracellular Mg2+ (*, P<0.05; **, P<0.01). Crosses on open symbols indicate statistically significant differences compared to the filled symbols at the same time point (†, P<0.05;††, P<0.01).

Mentions: Changes in [Mg2+]i and pHi during exposure to Ca2+- and Na+-free solutions are shown in Figures 4A and B, respectively. In the presence of 1.2 mM Mg2+ (the ‘normal’Mg2+ concentration in extracellular medium), [Mg2+]i increased from 0.73±0.07 to 1.01±0.09 mM after 125 min (▪; n= 5; P<0.01). When the concentration of extracellular Mg2+ was increased to 6.0 mM, [Mg2+]i increased from 0.78±0.08 to 1.79 ± 0.18 mM after 125 min (□; n= 7; P<0.01). The [Mg2+]i rise was clearly enhanced by raising the extracellular Mg2+ concentration (unpaired t-test, P<0.01).


Na(+)-independent Mg(2+) transport sensitive to 2-aminoethoxydiphenyl borate (2-APB) in vascular smooth muscle cells: involvement of TRPM-like channels.

Hamaguchi Y, Matsubara T, Amano T, Uetani T, Asano H, Iwamoto T, Furukawa K, Murohara T, Nakayama S - J. Cell. Mol. Med. (2008)

Changes in [Mg2+]i (A) and pHi (B) during exposures to Ca2+- and Na+-free solutions containing Mg2+. After the carotid artery preparations were superfused with a Ca2+-free solution containing 1.2 mM Mg2+, extra-cellular Na+ was removed for 125 min (filled symbols: ▪, •). In the experiments indicated by open symbols (□, ○), extracellular Mg2+ was increased to 6.0 mM during Na+ removal. Asterisks indicate statistically significant differences compared to the [Mg2+]i and pHi values before removal of extracellular Mg2+ (*, P<0.05; **, P<0.01). Crosses on open symbols indicate statistically significant differences compared to the filled symbols at the same time point (†, P<0.05;††, P<0.01).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4401140&req=5

fig04: Changes in [Mg2+]i (A) and pHi (B) during exposures to Ca2+- and Na+-free solutions containing Mg2+. After the carotid artery preparations were superfused with a Ca2+-free solution containing 1.2 mM Mg2+, extra-cellular Na+ was removed for 125 min (filled symbols: ▪, •). In the experiments indicated by open symbols (□, ○), extracellular Mg2+ was increased to 6.0 mM during Na+ removal. Asterisks indicate statistically significant differences compared to the [Mg2+]i and pHi values before removal of extracellular Mg2+ (*, P<0.05; **, P<0.01). Crosses on open symbols indicate statistically significant differences compared to the filled symbols at the same time point (†, P<0.05;††, P<0.01).
Mentions: Changes in [Mg2+]i and pHi during exposure to Ca2+- and Na+-free solutions are shown in Figures 4A and B, respectively. In the presence of 1.2 mM Mg2+ (the ‘normal’Mg2+ concentration in extracellular medium), [Mg2+]i increased from 0.73±0.07 to 1.01±0.09 mM after 125 min (▪; n= 5; P<0.01). When the concentration of extracellular Mg2+ was increased to 6.0 mM, [Mg2+]i increased from 0.78±0.08 to 1.79 ± 0.18 mM after 125 min (□; n= 7; P<0.01). The [Mg2+]i rise was clearly enhanced by raising the extracellular Mg2+ concentration (unpaired t-test, P<0.01).

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Cardiology, Nagoya University Graduate School of Medicine, Nagoya, Japan.

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.

Show MeSH
Related in: MedlinePlus