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Figure 6. Effects of exercise training on aging-induced alteration of MaxiK channel activity and gating properties in mesenteric artery myocytes. (A–C) Representative recordings of single-channel currents at a membrane voltage of +40 mV in Young, O-SED, and O-EX groups (1 μM [Ca<sup>2+</sup>]<sub>free</sub> in the bath solution), respectively. (D–F) Summary of the MaxiK channel conductance, normalized Np<sub>o</sub>, and time constant, respectively. (G) Effect of tamoxifen (1 μM) on MaxiK channel activity in three groups. Bar plot summarizes the mean ± SEM fold change in the normalized Np<sub>o</sub> of MaxiK channels after the application of Tam. [Ca<sup>2+</sup>]<sub>free</sub> in the bath solution: 0.1 μM. Holding potential = + 40 mV. *p < .01, compared with Young group. <sup>#</sup>p < .01, compared with O-SED group; n = 6 in each group. τ<sub>o</sub>, time constant of open state; τ<sub>c</sub>, time constant of close state. From: Exercise Training Reverses Unparallel Downregulation of MaxiK Channel α- and β1-Subunit to Enhance Vascular Function in Aging Mesenteric Arteries J Gerontol A Biol Sci Med Sci. 2013;69(12): doi: /gerona/glt205 J Gerontol A Biol Sci Med Sci | © The Author Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please
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Figure 1. Effect of exercise on norepinephrine (NE)–induced cardiovascular responses in Young, O-SED, and O-EX rats. (A, C, and E) NE-induced systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) responses, respectively. 0 min: time for intravenous injection of NE (18 μg/kg). *p < .05, compared with the baseline level. (B, D, and F) The maximal change of the SBP (ΔSBP), DBP (ΔDBP), and HR (ΔHR), respectively. *p < .05, compared with Young; <sup>#</sup>p < .05, compared with O-SED; n = 6 in each group. From: Exercise Training Reverses Unparallel Downregulation of MaxiK Channel α- and β1-Subunit to Enhance Vascular Function in Aging Mesenteric Arteries J Gerontol A Biol Sci Med Sci. 2013;69(12): doi: /gerona/glt205 J Gerontol A Biol Sci Med Sci | © The Author Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please
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Figure 2. Effects of MaxiK channel inhibitor iberiotoxin (IbTX) on the norepinephrine (NE)–induced vessel contraction in mesenteric arteries from Young, O-SED, and O-EX rats. Vessels were first contracted with 10<sup>−5</sup> M NE (gray traces). Following washing and reequilibration to basal tones (45 minutes later), the vessel were pretreated with IbTX (10<sup>−8</sup> M) for 2 minutes and then stimulated with 10<sup>−5</sup> M NE in the presence of IbTX (black traces). The representative vessel contraction traces were shown in A (Young), B (O-SED), and C (O-EX). (D) Statistic diagram of IbTX pretreatment on the NE-induced vessel contraction. *p < .05, compared with NE-induced tension in the same group; <sup>#</sup>p < .05, compared with Young. (E) The maximal increase of NE-induced vessel contraction (ΔNE) in three groups. *p < .05, compared with Young; <sup>#</sup>p < .05, compared with O-SED; n = 6 in each group. From: Exercise Training Reverses Unparallel Downregulation of MaxiK Channel α- and β1-Subunit to Enhance Vascular Function in Aging Mesenteric Arteries J Gerontol A Biol Sci Med Sci. 2013;69(12): doi: /gerona/glt205 J Gerontol A Biol Sci Med Sci | © The Author Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please
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Figure 3. Whole-cell K<sup>+</sup> currents in myocytes of MA measured using the conventional whole-cell configuration of the patch clamp technique. (A) Young; (B) O-SED; (C) O-EX. (a) Typical recordings of whole-cell K<sup>+</sup> currents measured during depolarizing voltage steps. (b) Whole-cell K<sup>+</sup> current measured after the treatment of IbTX (100nM) for 10 minutes. (c) The mean current density vs voltage plot in the absence (closed circles, n = 6) or presence (open circles, n = 6) of IbTX in myocytes from three groups. From: Exercise Training Reverses Unparallel Downregulation of MaxiK Channel α- and β1-Subunit to Enhance Vascular Function in Aging Mesenteric Arteries J Gerontol A Biol Sci Med Sci. 2013;69(12): doi: /gerona/glt205 J Gerontol A Biol Sci Med Sci | © The Author Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please
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Figure 4. Measurement of spontaneous transient outward current (STOC) activity in freshly isolated MA myocytes from Young, O-SED, and O-EX rats. STOCs were recorded by means of the perforated patch clamp technique. (A) Representative STOC recordings in Young animals. Depolarizing test potentials were gradually increased in 10 mV increments from −40 to 0 mV. (B) Expanded traces of STOCs at holding potential of −30 mV in three groups. (C and D) Summarized data of STOC amplitude (C) and frequency (D) at membrane potential of −30 mV. *p < .01, compared with Young group<sub>;</sub><sup> #</sup>p < .01, compared with O-SED group; n = 6 in each group. From: Exercise Training Reverses Unparallel Downregulation of MaxiK Channel α- and β1-Subunit to Enhance Vascular Function in Aging Mesenteric Arteries J Gerontol A Biol Sci Med Sci. 2013;69(12): doi: /gerona/glt205 J Gerontol A Biol Sci Med Sci | © The Author Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please
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Figure 5. Effect of exercise training on Ca<sup>2+</sup>/voltage sensitivity of MaxiK channel in mesenteric artery myocytes from Young, O-SED, and O-EX groups. (A) Voltage dependence of MaxiK channel in the 1 μM Ca<sup>2+</sup>. The line was drawn according to the best fits with the Boltzmann equation. (B) Effect of exercise training on Ca<sup>2+</sup> dependence of MaxiK channel. The data points were fitted with the Hill equation to obtain the calcium concentration necessary to open half of the channels (K<sub>d</sub>) and the Hill coefficient(η<sup>H</sup>); n = 6 in each group. From: Exercise Training Reverses Unparallel Downregulation of MaxiK Channel α- and β1-Subunit to Enhance Vascular Function in Aging Mesenteric Arteries J Gerontol A Biol Sci Med Sci. 2013;69(12): doi: /gerona/glt205 J Gerontol A Biol Sci Med Sci | © The Author Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please
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Figure 7. Expression of MaxiK channel α-subunit and β1-subunit in mesenteric smooth muscle membranes from Young, O-SED, and O-EX groups. Each lane was loaded with 20 μL (2 μg/μL) of supernatant from mesenteric arteries (MAs). (A) Immunoreactive bands corresponding to α-subunit, β1-subunit, and β-actin in the MA myocytes detected by Western blot. (B and C) Summarized data of α-subunit (B) and β1-subunit (C) protein levels expressed as a ratio to β-actin. (D) Summarized β1/α ratio; n = 6 in each group. *p < .01, compared with Young group<sub>;</sub><sup>#</sup>p < .01, compared with O-SED group. From: Exercise Training Reverses Unparallel Downregulation of MaxiK Channel α- and β1-Subunit to Enhance Vascular Function in Aging Mesenteric Arteries J Gerontol A Biol Sci Med Sci. 2013;69(12): doi: /gerona/glt205 J Gerontol A Biol Sci Med Sci | © The Author Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please
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