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Diverse Kir expression contributes to distinct bimodal distribution of resting potentials and vasotone responses of arterioles.

Yang Y, Chen F, Karasawa T, Ma KT, Guan BC, Shi XR, Li H, Steyger PS, Nuttall AL, Jiang ZG - PLoS ONE (2015)

Bottom Line: We compared the RPs and vasomotion properties between the guinea pig spiral modiolar artery (SMA), brain arterioles (BA) and mesenteric arteries (MA).We found: 1) RPs showed a robust bimodal distribution peaked at -76 and -40 mV evenly in the SMA, unevenly at -77 and -51 mV in the BA and ~-71 and -52 mV in the MA.We conclude that a dense expression of functional Kir2.X channels underlies the more negative RPs in endothelial cells and a subset of VSMC in these arterioles, and the heterogeneous Kir function is primarily responsible for the distinct bimodal RPs among these arterioles.

View Article: PubMed Central - PubMed

Affiliation: Oregon Hearing Research Center, Oregon Health & Science University, Portland, OR, 97239, United States of America.

ABSTRACT
The resting membrane potential (RP) of vascular smooth muscle cells (VSMCs) is a major determinant of cytosolic calcium concentration and vascular tone. The heterogeneity of RPs and its underlying mechanism among different vascular beds remain poorly understood. We compared the RPs and vasomotion properties between the guinea pig spiral modiolar artery (SMA), brain arterioles (BA) and mesenteric arteries (MA). We found: 1) RPs showed a robust bimodal distribution peaked at -76 and -40 mV evenly in the SMA, unevenly at -77 and -51 mV in the BA and ~-71 and -52 mV in the MA. Ba(2+) 0.1 mM eliminated their high RP peaks ~-75 mV. 2) Cells with low RP (~-45 mV) hyperpolarized in response to 10 mM extracellular K(+), while cells with a high RP depolarized, and cells with intermediate RP (~-58 mV) displayed an initial hyperpolarization followed by prolonged depolarization. Moderate high K(+) typically induced dilation, constriction and a dilation followed by constriction in the SMA, MA and BA, respectively. 3) Boltzmann-fit analysis of the Ba(2+)-sensitive inward rectifier K(+) (Kir) whole-cell current showed that the maximum Kir conductance density significantly differed among the vessels, and the half-activation voltage was significantly more negative in the MA. 4) Corresponding to the whole-cell data, computational modeling simulated the three RP distribution patterns and the dynamics of RP changes obtained experimentally, including the regenerative swift shifts between the two RP levels after reaching a threshold. 5) Molecular works revealed strong Kir2.1 and Kir2.2 transcripts and Kir2.1 immunolabeling in all 3 vessels, while Kir2.3 and Kir2.4 transcript levels varied. We conclude that a dense expression of functional Kir2.X channels underlies the more negative RPs in endothelial cells and a subset of VSMC in these arterioles, and the heterogeneous Kir function is primarily responsible for the distinct bimodal RPs among these arterioles. The fast Kir-based regenerative shifts between two RP states could form a critical mechanism for conduction/spread of vasomotion along the arteriole axis.

No MeSH data available.


Related in: MedlinePlus

Measurement of Kir parameters at 3 extracellular K+-concentrations for SMA ECs.(A) Chart trace of HC at -20 mV, showing the experimental protocol. The vertical deflections were caused by repeated ramp commands (b, c, f, h, i, l) and step commands (a, d, e, g, j, k) for construction of I/V curves. (B) Step-induced whole-cell currents revealed a significant inward rectification in control (B.a, 5 mM K+), which was not affected by the cocktail solution (B.d) but enhanced by 20 mM and 60 mM K+ (e and g, respectively), and suppressed by added 0.1 mM Ba2+ (B.j and B.k). (C) Ramp-constructed whole-cell I/V curves in 5, 20 and 60 mM K+ (c, f, h) and in added 0.1 mM Ba2+ (i,l; l was removed for clarity), depicting the same results as in B. (D-F) The I/V curves of the net Ba2+-sensitive currents in the three [K+]os. The overlapping smooth curves are the least square fit of Boltzmann function to I/Vs (see Fig 5 legend). The curve fitting revealed Kir parameters as Gmax = 1.34 nS, V0.5 = -59 mV, a slope factor k = 15.9 mV/e-fold in 5 mM K+ (D). In 20 and 60 mM K+ (E, F), Gmax = 1.67 and 3.07 nS; V0.5 = -44 and -17 mV; and k = 10.2 and 7.2 mV/e-fold, respectively. (G) Voltage-dependency plot of the Kir conductance in the three [K+]os. Arrows (↑) denote the EK, respectively. The recorded cell was located within a short EC tubule having an input capacitance Cm of 78 pF and the capacitive transient was fitted with a single term exponential function, indicating tight electrical coupling of multiple ECs (also see [41])
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pone.0125266.g005: Measurement of Kir parameters at 3 extracellular K+-concentrations for SMA ECs.(A) Chart trace of HC at -20 mV, showing the experimental protocol. The vertical deflections were caused by repeated ramp commands (b, c, f, h, i, l) and step commands (a, d, e, g, j, k) for construction of I/V curves. (B) Step-induced whole-cell currents revealed a significant inward rectification in control (B.a, 5 mM K+), which was not affected by the cocktail solution (B.d) but enhanced by 20 mM and 60 mM K+ (e and g, respectively), and suppressed by added 0.1 mM Ba2+ (B.j and B.k). (C) Ramp-constructed whole-cell I/V curves in 5, 20 and 60 mM K+ (c, f, h) and in added 0.1 mM Ba2+ (i,l; l was removed for clarity), depicting the same results as in B. (D-F) The I/V curves of the net Ba2+-sensitive currents in the three [K+]os. The overlapping smooth curves are the least square fit of Boltzmann function to I/Vs (see Fig 5 legend). The curve fitting revealed Kir parameters as Gmax = 1.34 nS, V0.5 = -59 mV, a slope factor k = 15.9 mV/e-fold in 5 mM K+ (D). In 20 and 60 mM K+ (E, F), Gmax = 1.67 and 3.07 nS; V0.5 = -44 and -17 mV; and k = 10.2 and 7.2 mV/e-fold, respectively. (G) Voltage-dependency plot of the Kir conductance in the three [K+]os. Arrows (↑) denote the EK, respectively. The recorded cell was located within a short EC tubule having an input capacitance Cm of 78 pF and the capacitive transient was fitted with a single term exponential function, indicating tight electrical coupling of multiple ECs (also see [41])

Mentions: Whole-cell voltage-clamp recordings were conducted in more than 100 cells from each vessel that were dissociated or in situ within a short arteriolar segment; in the latter cases, the cells were less enzyme- and trituration-treated (e.g., Fig 4 vs. Fig 5, also see [40,41]. The general membrane properties of these cells were similar to those published previously (Table 1 in [41]). Briefly, in situ cells typically exhibited a low input resistance (~0.5 GΩ for the SMA and BA, ~0.3 GΩ for the MA) or higher input conductance, high input capacitance (about 70, 150 and 250 pF for the SMA, BA and MA), than dissociated cells (about 3.5, 3.5 and 3 GΩ; 6, 9 and 13 pF for the SMA, BA and MA, respectively), indicative of ubiquitous gap junction-coupling in the three arteriole beds but with tighter electrical coupling in the MA than the BA or SMA (S1 Fig). Gap junction-mediated electrical coupling was blocked by 30 μM 18β-glycyrrhetinic acid (18βGA), resulting in a complete electrical isolation of the recorded cells in all three vessel types [40,41].


Diverse Kir expression contributes to distinct bimodal distribution of resting potentials and vasotone responses of arterioles.

Yang Y, Chen F, Karasawa T, Ma KT, Guan BC, Shi XR, Li H, Steyger PS, Nuttall AL, Jiang ZG - PLoS ONE (2015)

Measurement of Kir parameters at 3 extracellular K+-concentrations for SMA ECs.(A) Chart trace of HC at -20 mV, showing the experimental protocol. The vertical deflections were caused by repeated ramp commands (b, c, f, h, i, l) and step commands (a, d, e, g, j, k) for construction of I/V curves. (B) Step-induced whole-cell currents revealed a significant inward rectification in control (B.a, 5 mM K+), which was not affected by the cocktail solution (B.d) but enhanced by 20 mM and 60 mM K+ (e and g, respectively), and suppressed by added 0.1 mM Ba2+ (B.j and B.k). (C) Ramp-constructed whole-cell I/V curves in 5, 20 and 60 mM K+ (c, f, h) and in added 0.1 mM Ba2+ (i,l; l was removed for clarity), depicting the same results as in B. (D-F) The I/V curves of the net Ba2+-sensitive currents in the three [K+]os. The overlapping smooth curves are the least square fit of Boltzmann function to I/Vs (see Fig 5 legend). The curve fitting revealed Kir parameters as Gmax = 1.34 nS, V0.5 = -59 mV, a slope factor k = 15.9 mV/e-fold in 5 mM K+ (D). In 20 and 60 mM K+ (E, F), Gmax = 1.67 and 3.07 nS; V0.5 = -44 and -17 mV; and k = 10.2 and 7.2 mV/e-fold, respectively. (G) Voltage-dependency plot of the Kir conductance in the three [K+]os. Arrows (↑) denote the EK, respectively. The recorded cell was located within a short EC tubule having an input capacitance Cm of 78 pF and the capacitive transient was fitted with a single term exponential function, indicating tight electrical coupling of multiple ECs (also see [41])
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4418701&req=5

pone.0125266.g005: Measurement of Kir parameters at 3 extracellular K+-concentrations for SMA ECs.(A) Chart trace of HC at -20 mV, showing the experimental protocol. The vertical deflections were caused by repeated ramp commands (b, c, f, h, i, l) and step commands (a, d, e, g, j, k) for construction of I/V curves. (B) Step-induced whole-cell currents revealed a significant inward rectification in control (B.a, 5 mM K+), which was not affected by the cocktail solution (B.d) but enhanced by 20 mM and 60 mM K+ (e and g, respectively), and suppressed by added 0.1 mM Ba2+ (B.j and B.k). (C) Ramp-constructed whole-cell I/V curves in 5, 20 and 60 mM K+ (c, f, h) and in added 0.1 mM Ba2+ (i,l; l was removed for clarity), depicting the same results as in B. (D-F) The I/V curves of the net Ba2+-sensitive currents in the three [K+]os. The overlapping smooth curves are the least square fit of Boltzmann function to I/Vs (see Fig 5 legend). The curve fitting revealed Kir parameters as Gmax = 1.34 nS, V0.5 = -59 mV, a slope factor k = 15.9 mV/e-fold in 5 mM K+ (D). In 20 and 60 mM K+ (E, F), Gmax = 1.67 and 3.07 nS; V0.5 = -44 and -17 mV; and k = 10.2 and 7.2 mV/e-fold, respectively. (G) Voltage-dependency plot of the Kir conductance in the three [K+]os. Arrows (↑) denote the EK, respectively. The recorded cell was located within a short EC tubule having an input capacitance Cm of 78 pF and the capacitive transient was fitted with a single term exponential function, indicating tight electrical coupling of multiple ECs (also see [41])
Mentions: Whole-cell voltage-clamp recordings were conducted in more than 100 cells from each vessel that were dissociated or in situ within a short arteriolar segment; in the latter cases, the cells were less enzyme- and trituration-treated (e.g., Fig 4 vs. Fig 5, also see [40,41]. The general membrane properties of these cells were similar to those published previously (Table 1 in [41]). Briefly, in situ cells typically exhibited a low input resistance (~0.5 GΩ for the SMA and BA, ~0.3 GΩ for the MA) or higher input conductance, high input capacitance (about 70, 150 and 250 pF for the SMA, BA and MA), than dissociated cells (about 3.5, 3.5 and 3 GΩ; 6, 9 and 13 pF for the SMA, BA and MA, respectively), indicative of ubiquitous gap junction-coupling in the three arteriole beds but with tighter electrical coupling in the MA than the BA or SMA (S1 Fig). Gap junction-mediated electrical coupling was blocked by 30 μM 18β-glycyrrhetinic acid (18βGA), resulting in a complete electrical isolation of the recorded cells in all three vessel types [40,41].

Bottom Line: We compared the RPs and vasomotion properties between the guinea pig spiral modiolar artery (SMA), brain arterioles (BA) and mesenteric arteries (MA).We found: 1) RPs showed a robust bimodal distribution peaked at -76 and -40 mV evenly in the SMA, unevenly at -77 and -51 mV in the BA and ~-71 and -52 mV in the MA.We conclude that a dense expression of functional Kir2.X channels underlies the more negative RPs in endothelial cells and a subset of VSMC in these arterioles, and the heterogeneous Kir function is primarily responsible for the distinct bimodal RPs among these arterioles.

View Article: PubMed Central - PubMed

Affiliation: Oregon Hearing Research Center, Oregon Health & Science University, Portland, OR, 97239, United States of America.

ABSTRACT
The resting membrane potential (RP) of vascular smooth muscle cells (VSMCs) is a major determinant of cytosolic calcium concentration and vascular tone. The heterogeneity of RPs and its underlying mechanism among different vascular beds remain poorly understood. We compared the RPs and vasomotion properties between the guinea pig spiral modiolar artery (SMA), brain arterioles (BA) and mesenteric arteries (MA). We found: 1) RPs showed a robust bimodal distribution peaked at -76 and -40 mV evenly in the SMA, unevenly at -77 and -51 mV in the BA and ~-71 and -52 mV in the MA. Ba(2+) 0.1 mM eliminated their high RP peaks ~-75 mV. 2) Cells with low RP (~-45 mV) hyperpolarized in response to 10 mM extracellular K(+), while cells with a high RP depolarized, and cells with intermediate RP (~-58 mV) displayed an initial hyperpolarization followed by prolonged depolarization. Moderate high K(+) typically induced dilation, constriction and a dilation followed by constriction in the SMA, MA and BA, respectively. 3) Boltzmann-fit analysis of the Ba(2+)-sensitive inward rectifier K(+) (Kir) whole-cell current showed that the maximum Kir conductance density significantly differed among the vessels, and the half-activation voltage was significantly more negative in the MA. 4) Corresponding to the whole-cell data, computational modeling simulated the three RP distribution patterns and the dynamics of RP changes obtained experimentally, including the regenerative swift shifts between the two RP levels after reaching a threshold. 5) Molecular works revealed strong Kir2.1 and Kir2.2 transcripts and Kir2.1 immunolabeling in all 3 vessels, while Kir2.3 and Kir2.4 transcript levels varied. We conclude that a dense expression of functional Kir2.X channels underlies the more negative RPs in endothelial cells and a subset of VSMC in these arterioles, and the heterogeneous Kir function is primarily responsible for the distinct bimodal RPs among these arterioles. The fast Kir-based regenerative shifts between two RP states could form a critical mechanism for conduction/spread of vasomotion along the arteriole axis.

No MeSH data available.


Related in: MedlinePlus