TY - JOUR
T1 - Knockout of Na+/Ca2+ exchanger in smooth muscle attenuates vasoconstriction and L-type Ca2+ channel current and lowers blood pressure
AU - Zhang, Jin
AU - Ren, Chongyu
AU - Chen, Ling
AU - Navedo, Manuel F
AU - Antos, Laura K.
AU - Kinsey, Stephen P.
AU - Iwamoto, Takahiro
AU - Philipson, Kenneth D.
AU - Kotlikoff, Michael I.
AU - Santana, Luis Fernando
AU - Wier, W. Gil
AU - Matteson, Donald R.
AU - Blaustein, Mordecai P.
PY - 2010/5
Y1 - 2010/5
N2 - Mice with smooth muscle (SM)-specific knockout of Na+/Ca 2+ exchanger type-1 (NCX1SM-/-) and the NCX inhibitor, SEA0400, were used to study the physiological role of NCX1 in mouse mesenteric arteries. NCX1 protein expression was greatly reduced in arteries from NCX1 SM-/- mice generated with Cre recombinase. Mean blood pressure (BP) was 6-10 mmHg lower in NCX1SM-/- mice than in wild-type (WT) controls. Vasoconstriction was studied in isolated, pressurized mesenteric small arteries from WT and NCX1SM-/- mice and in heterozygotes with a global null mutation (NCX1Fx/-). Reduced NCX1 activity was manifested by a marked attenuation of responses to low extracellular Na+ concentration, nanomolar ouabain, and SEA0400. Myogenic tone (MT, 70 mmHg) was reduced by ∼15% in NCX1SM-/- arteries and, to a similar extent, by SEA0400 in WT arteries. MT was normal in arteries from NCX1Fx/- mice, which had normal BP. Vasoconstrictions to phenylephrine and elevated extracellular K+ concentration were significantly reduced in NCX1SM-/- arteries. Because a high extracellular K+ concentration-induced vasoconstriction involves the activation of L-type voltage-gated Ca2+ channels (LVGCs), we measured LVGC-mediated currents and Ca2+ sparklets in isolated mesenteric artery myocytes. Both the currents and the sparklets were significantly reduced in NCX1 SM-/- (vs. WT or NCX1Fx/-) myocytes, but the voltage-dependent inactivation of LVGCs was not augmented. An acute application of SEA0400 in WT myocytes had no effect on LVGC current. The LVGC agonist, Bay K 8644, eliminated the differences in LVGC currents and Ca2+ sparklets between NCX1SM-/- and control myocytes, suggesting that LVGC expression was normal in NCX1SM-/- myocytes. Bay K 8644 did not, however, eliminate the difference in myogenic constriction between WT and NCX1SM-/- arteries. We conclude that, under physiological conditions, NCX1-mediated Ca2+ entry contributes significantly to the maintenance of MT. In NCX1SM-/- mouse artery myocytes, the reduced Ca2+ entry via NCX1 may lower cytosolic Ca2+ concentration and thereby reduce MT and BP. The reduced LVGC activity may be the consequence of a low cytosolic Ca2+ concentration.
AB - Mice with smooth muscle (SM)-specific knockout of Na+/Ca 2+ exchanger type-1 (NCX1SM-/-) and the NCX inhibitor, SEA0400, were used to study the physiological role of NCX1 in mouse mesenteric arteries. NCX1 protein expression was greatly reduced in arteries from NCX1 SM-/- mice generated with Cre recombinase. Mean blood pressure (BP) was 6-10 mmHg lower in NCX1SM-/- mice than in wild-type (WT) controls. Vasoconstriction was studied in isolated, pressurized mesenteric small arteries from WT and NCX1SM-/- mice and in heterozygotes with a global null mutation (NCX1Fx/-). Reduced NCX1 activity was manifested by a marked attenuation of responses to low extracellular Na+ concentration, nanomolar ouabain, and SEA0400. Myogenic tone (MT, 70 mmHg) was reduced by ∼15% in NCX1SM-/- arteries and, to a similar extent, by SEA0400 in WT arteries. MT was normal in arteries from NCX1Fx/- mice, which had normal BP. Vasoconstrictions to phenylephrine and elevated extracellular K+ concentration were significantly reduced in NCX1SM-/- arteries. Because a high extracellular K+ concentration-induced vasoconstriction involves the activation of L-type voltage-gated Ca2+ channels (LVGCs), we measured LVGC-mediated currents and Ca2+ sparklets in isolated mesenteric artery myocytes. Both the currents and the sparklets were significantly reduced in NCX1 SM-/- (vs. WT or NCX1Fx/-) myocytes, but the voltage-dependent inactivation of LVGCs was not augmented. An acute application of SEA0400 in WT myocytes had no effect on LVGC current. The LVGC agonist, Bay K 8644, eliminated the differences in LVGC currents and Ca2+ sparklets between NCX1SM-/- and control myocytes, suggesting that LVGC expression was normal in NCX1SM-/- myocytes. Bay K 8644 did not, however, eliminate the difference in myogenic constriction between WT and NCX1SM-/- arteries. We conclude that, under physiological conditions, NCX1-mediated Ca2+ entry contributes significantly to the maintenance of MT. In NCX1SM-/- mouse artery myocytes, the reduced Ca2+ entry via NCX1 may lower cytosolic Ca2+ concentration and thereby reduce MT and BP. The reduced LVGC activity may be the consequence of a low cytosolic Ca2+ concentration.
KW - Bay K 8644
KW - Calcium sparklets
KW - Mesenteric arteries
KW - Myogenic tone
KW - Patch clamp
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U2 - 10.1152/ajpheart.00964.2009
DO - 10.1152/ajpheart.00964.2009
M3 - Article
C2 - 20173044
AN - SCOPUS:77951864034
VL - 298
JO - American Journal of Physiology - Renal Fluid and Electrolyte Physiology
JF - American Journal of Physiology - Renal Fluid and Electrolyte Physiology
SN - 1931-857X
IS - 5
ER -