Influence of extracellular Na+ removal on cytosolic Ca2+ concentration in smooth muscle cells of rabbit cerebral artery

J. K. Kim, Sungjoon Kim, Y. C. Kim, Insuk So, K. W. Kim

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Abstract

There are some controversies over the contribution of Na+/Ca2+ exchanger (NCX) to the regulation of cytosolic Ca2+ concentration ([Ca2+](c)) in smooth muscle. To prove the functional role of Na+/Ca2+ exchanger, we examined whether the removal of extracellular Na+ could affect [Ca2+](c) of rabbit cerebral arterial smooth muscle. The fluorescence ratio of fura-2 (R(340/380)) was measured in the single myocyte of rabbit middle cerebral artery and Na+ was substituted with the same concentration of NMDG+ or Li+. In 21 out of 230 cells tested, Na+-removal increased R(340/380) (ΔR(340/380)) by 115 ± 16.5% of the ΔR340/380 induced by 10 mM caffeine in the same cell. The Na+ removal-induced ΔR(340/380) was blocked by a selective inhibitor of cardiac type NCX exchanger (KB-R7943, (2-[2-[4- (4-nitrobenzyloxy) phenyl]ethyl]isothiourea, 10 μM). In those cells where the Na+-removal by itself did not increase R(340/380), the caffeine-induced ΔR(340/380) was increased by Na+-removal (130 ± 9.8% of control response, n=30). Under the whole-cell patch clamp condition, short application of caffeine induced transient increase of outward current (I(K,Ca)-transient) which reflect the change of subsarcolemmal [Ca2+]. The application of KB- R7943 increased the amplitude of I(K,Ca)-transient (n=4). These results suggest the functional existence of NCX in rabbit cerebral artery smooth muscle.

Original languageEnglish
Pages (from-to)135-145
Number of pages11
JournalJournal of Smooth Muscle Research
Volume35
Issue number5-6
StatePublished - 1 Dec 1999

Fingerprint

Cerebral Arteries
Smooth Muscle Myocytes
Caffeine
Rabbits
Smooth Muscle
Fura-2
Middle Cerebral Artery
Muscle Cells
Fluorescence
2-(2-(4-(4-nitrobenzyloxy)phenyl)ethyl)isothiourea methanesulfonate

Keywords

  • Cytosolic Ca concentration
  • Na/Ca exchanger
  • Smooth muscle cell

Cite this

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title = "Influence of extracellular Na+ removal on cytosolic Ca2+ concentration in smooth muscle cells of rabbit cerebral artery",
abstract = "There are some controversies over the contribution of Na+/Ca2+ exchanger (NCX) to the regulation of cytosolic Ca2+ concentration ([Ca2+](c)) in smooth muscle. To prove the functional role of Na+/Ca2+ exchanger, we examined whether the removal of extracellular Na+ could affect [Ca2+](c) of rabbit cerebral arterial smooth muscle. The fluorescence ratio of fura-2 (R(340/380)) was measured in the single myocyte of rabbit middle cerebral artery and Na+ was substituted with the same concentration of NMDG+ or Li+. In 21 out of 230 cells tested, Na+-removal increased R(340/380) (ΔR(340/380)) by 115 ± 16.5{\%} of the ΔR340/380 induced by 10 mM caffeine in the same cell. The Na+ removal-induced ΔR(340/380) was blocked by a selective inhibitor of cardiac type NCX exchanger (KB-R7943, (2-[2-[4- (4-nitrobenzyloxy) phenyl]ethyl]isothiourea, 10 μM). In those cells where the Na+-removal by itself did not increase R(340/380), the caffeine-induced ΔR(340/380) was increased by Na+-removal (130 ± 9.8{\%} of control response, n=30). Under the whole-cell patch clamp condition, short application of caffeine induced transient increase of outward current (I(K,Ca)-transient) which reflect the change of subsarcolemmal [Ca2+]. The application of KB- R7943 increased the amplitude of I(K,Ca)-transient (n=4). These results suggest the functional existence of NCX in rabbit cerebral artery smooth muscle.",
keywords = "Cytosolic Ca concentration, Na/Ca exchanger, Smooth muscle cell",
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Influence of extracellular Na+ removal on cytosolic Ca2+ concentration in smooth muscle cells of rabbit cerebral artery. / Kim, J. K.; Kim, Sungjoon; Kim, Y. C.; So, Insuk; Kim, K. W.

In: Journal of Smooth Muscle Research, Vol. 35, No. 5-6, 01.12.1999, p. 135-145.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Influence of extracellular Na+ removal on cytosolic Ca2+ concentration in smooth muscle cells of rabbit cerebral artery

AU - Kim, J. K.

AU - Kim, Sungjoon

AU - Kim, Y. C.

AU - So, Insuk

AU - Kim, K. W.

PY - 1999/12/1

Y1 - 1999/12/1

N2 - There are some controversies over the contribution of Na+/Ca2+ exchanger (NCX) to the regulation of cytosolic Ca2+ concentration ([Ca2+](c)) in smooth muscle. To prove the functional role of Na+/Ca2+ exchanger, we examined whether the removal of extracellular Na+ could affect [Ca2+](c) of rabbit cerebral arterial smooth muscle. The fluorescence ratio of fura-2 (R(340/380)) was measured in the single myocyte of rabbit middle cerebral artery and Na+ was substituted with the same concentration of NMDG+ or Li+. In 21 out of 230 cells tested, Na+-removal increased R(340/380) (ΔR(340/380)) by 115 ± 16.5% of the ΔR340/380 induced by 10 mM caffeine in the same cell. The Na+ removal-induced ΔR(340/380) was blocked by a selective inhibitor of cardiac type NCX exchanger (KB-R7943, (2-[2-[4- (4-nitrobenzyloxy) phenyl]ethyl]isothiourea, 10 μM). In those cells where the Na+-removal by itself did not increase R(340/380), the caffeine-induced ΔR(340/380) was increased by Na+-removal (130 ± 9.8% of control response, n=30). Under the whole-cell patch clamp condition, short application of caffeine induced transient increase of outward current (I(K,Ca)-transient) which reflect the change of subsarcolemmal [Ca2+]. The application of KB- R7943 increased the amplitude of I(K,Ca)-transient (n=4). These results suggest the functional existence of NCX in rabbit cerebral artery smooth muscle.

AB - There are some controversies over the contribution of Na+/Ca2+ exchanger (NCX) to the regulation of cytosolic Ca2+ concentration ([Ca2+](c)) in smooth muscle. To prove the functional role of Na+/Ca2+ exchanger, we examined whether the removal of extracellular Na+ could affect [Ca2+](c) of rabbit cerebral arterial smooth muscle. The fluorescence ratio of fura-2 (R(340/380)) was measured in the single myocyte of rabbit middle cerebral artery and Na+ was substituted with the same concentration of NMDG+ or Li+. In 21 out of 230 cells tested, Na+-removal increased R(340/380) (ΔR(340/380)) by 115 ± 16.5% of the ΔR340/380 induced by 10 mM caffeine in the same cell. The Na+ removal-induced ΔR(340/380) was blocked by a selective inhibitor of cardiac type NCX exchanger (KB-R7943, (2-[2-[4- (4-nitrobenzyloxy) phenyl]ethyl]isothiourea, 10 μM). In those cells where the Na+-removal by itself did not increase R(340/380), the caffeine-induced ΔR(340/380) was increased by Na+-removal (130 ± 9.8% of control response, n=30). Under the whole-cell patch clamp condition, short application of caffeine induced transient increase of outward current (I(K,Ca)-transient) which reflect the change of subsarcolemmal [Ca2+]. The application of KB- R7943 increased the amplitude of I(K,Ca)-transient (n=4). These results suggest the functional existence of NCX in rabbit cerebral artery smooth muscle.

KW - Cytosolic Ca concentration

KW - Na/Ca exchanger

KW - Smooth muscle cell

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M3 - Article

VL - 35

SP - 135

EP - 145

JO - Journal of smooth muscle research = Nihon Heikatsukin Gakkai kikanshi

JF - Journal of smooth muscle research = Nihon Heikatsukin Gakkai kikanshi

SN - 0916-8737

IS - 5-6

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