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Ovariectomy-induced reductions in endothelial SK3 channel activity and endothelium-dependent vasorelaxation in murine mesenteric arteries.

Yap FC, Taylor MS, Lin MT - PLoS ONE (2014)

Bottom Line: The results from functional studies using isolated murine mesenteric arteries show that ovx reduces ACh-induced endothelium-dependent vasodilation due to decreased EDH and NO contributions, although the contribution of PGI2 is upregulated.The decreased EDH-mediated vasorelaxation in ovx vessels is due to reduced SK3 channel contribution to the pathway.Further, whole-cell recordings using dispersed endothelial cells also show reduced SK3 current density in ovx endothelial cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, University of South Alabama, Mobile, Alabama, United States of America.

ABSTRACT
Mesenteric artery endothelium expresses both small (SK3)- and intermediate (IK1)-conductance Ca(2+)-activated K(+) (KCa) channels whose activity modulates vascular tone via endothelium-dependent hyperpolarization (EDH). Two other major endothelium-dependent vasodilation pathways utilize nitric oxide (NO) and prostacyclin (PGI2). To examine how ovariectomy (ovx) affects the basal activity and acetylcholine (ACh)-induced activity of each of these three pathways to vasorelaxation, we used wire myograph and electrophysiological recordings. The results from functional studies using isolated murine mesenteric arteries show that ovx reduces ACh-induced endothelium-dependent vasodilation due to decreased EDH and NO contributions, although the contribution of PGI2 is upregulated. Both endothelial SK3 and IK1 channels are functionally coupled to TRPV4 (transient receptor potential, vanilloid type 4) channels: the activation of TRPV4 channels activates SK3 and IK1 channels, leading to EDH-mediated vascular relaxation. The decreased EDH-mediated vasorelaxation in ovx vessels is due to reduced SK3 channel contribution to the pathway. Further, whole-cell recordings using dispersed endothelial cells also show reduced SK3 current density in ovx endothelial cells. Consequently, activation of TRPV4 channels induces smaller changes in whole-cell current density. Thus, ovariectomy leads to a reduction in endothelial SK3 channel activity thereby reducing the SK3 contribution to EDH vasorelaxation.

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Ovariectomy reduces ACh-induced vasorelaxation.Representative force myograph traces showing isometric tension (mN) plotted against time (s) for both control (A) and ovariectomized (ovx; B) mesenteric vessels, and their concentration responses to both phenylephrine (PE; left panel) and acetylcholine (ACh; right panel). A and B: (left panel) Arrowheads and arrow markers show addition of different [PE] (from left to right: 0.1, 0.3, 0.7, 1, 3, 7, 10, and 30 µM); the arrow indicates the addition of 3 µM PE. (right panel) Following PE washout the vessels were ∼50% pre-contracted with PE and different [ACh] were added (markers from left to right: 0.01, 0.03, 0.1, 0.3, 1, 3 µM), with the arrow indicating 1 µM ACh. Normalized concentration-response of PE (C) and ACh (D) for both control (solid circles) and ovx (empty squares) vessels. Data were fitted with sigmoidal curves for both control (solid lines) and ovx (dotted lines) vessels. Both plots were normalized to the maximum PE-induced tension.
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pone-0104686-g001: Ovariectomy reduces ACh-induced vasorelaxation.Representative force myograph traces showing isometric tension (mN) plotted against time (s) for both control (A) and ovariectomized (ovx; B) mesenteric vessels, and their concentration responses to both phenylephrine (PE; left panel) and acetylcholine (ACh; right panel). A and B: (left panel) Arrowheads and arrow markers show addition of different [PE] (from left to right: 0.1, 0.3, 0.7, 1, 3, 7, 10, and 30 µM); the arrow indicates the addition of 3 µM PE. (right panel) Following PE washout the vessels were ∼50% pre-contracted with PE and different [ACh] were added (markers from left to right: 0.01, 0.03, 0.1, 0.3, 1, 3 µM), with the arrow indicating 1 µM ACh. Normalized concentration-response of PE (C) and ACh (D) for both control (solid circles) and ovx (empty squares) vessels. Data were fitted with sigmoidal curves for both control (solid lines) and ovx (dotted lines) vessels. Both plots were normalized to the maximum PE-induced tension.

Mentions: First- and second-order mesenteric arteries, obtained from age-matched female non-operated control and ovariectomized (ovx; 4–6 weeks post ovariectomy; see Methods for details) mice, were mounted in an isometric wire myograph system. Following equilibration for at least 30 min at 37°C vessels were stretched to their optimal isometric initial resting tension of ∼2 mN and a stable baseline was established for at least 10 min before experimentation. Bath applications of phenylephrine (PE) contracted both control and ovx mesenteric arteries in a concentration-dependent manner (Fig. 1 left). Normalized concentration-response curves (Figure 1C) showed no significant differences in the overall sensitivity to PE between control and ovx mice (EC50 values: control 1.0±0.1 µM vs. 1.2±0.1 µM; n = 10). Following bath washout, the same vessels were pre-contracted with PE to induce ∼50% increase in tension (EC50), followed by bath applications of different concentrations of acetylcholine (ACh), and the concentration-response curves of ACh-induced vasorelaxation for these vessels were also established (Fig. 1 right). ACh-induced vasorelaxation was normalized to PE-induced contraction and fitted with sigmoidal curves for both control and ovx groups. Despite having similar IC50 values (control: 0.21±0.01 µM vs. ovx: 0.20±0.02 µM; n = 10), maximal ACh-induced vasorelaxation was reduced in vessels isolated from ovx animals (tension at 1 µM: control: 26.5% vs. ovx 46.9%; Fig. 1D).


Ovariectomy-induced reductions in endothelial SK3 channel activity and endothelium-dependent vasorelaxation in murine mesenteric arteries.

Yap FC, Taylor MS, Lin MT - PLoS ONE (2014)

Ovariectomy reduces ACh-induced vasorelaxation.Representative force myograph traces showing isometric tension (mN) plotted against time (s) for both control (A) and ovariectomized (ovx; B) mesenteric vessels, and their concentration responses to both phenylephrine (PE; left panel) and acetylcholine (ACh; right panel). A and B: (left panel) Arrowheads and arrow markers show addition of different [PE] (from left to right: 0.1, 0.3, 0.7, 1, 3, 7, 10, and 30 µM); the arrow indicates the addition of 3 µM PE. (right panel) Following PE washout the vessels were ∼50% pre-contracted with PE and different [ACh] were added (markers from left to right: 0.01, 0.03, 0.1, 0.3, 1, 3 µM), with the arrow indicating 1 µM ACh. Normalized concentration-response of PE (C) and ACh (D) for both control (solid circles) and ovx (empty squares) vessels. Data were fitted with sigmoidal curves for both control (solid lines) and ovx (dotted lines) vessels. Both plots were normalized to the maximum PE-induced tension.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4126749&req=5

pone-0104686-g001: Ovariectomy reduces ACh-induced vasorelaxation.Representative force myograph traces showing isometric tension (mN) plotted against time (s) for both control (A) and ovariectomized (ovx; B) mesenteric vessels, and their concentration responses to both phenylephrine (PE; left panel) and acetylcholine (ACh; right panel). A and B: (left panel) Arrowheads and arrow markers show addition of different [PE] (from left to right: 0.1, 0.3, 0.7, 1, 3, 7, 10, and 30 µM); the arrow indicates the addition of 3 µM PE. (right panel) Following PE washout the vessels were ∼50% pre-contracted with PE and different [ACh] were added (markers from left to right: 0.01, 0.03, 0.1, 0.3, 1, 3 µM), with the arrow indicating 1 µM ACh. Normalized concentration-response of PE (C) and ACh (D) for both control (solid circles) and ovx (empty squares) vessels. Data were fitted with sigmoidal curves for both control (solid lines) and ovx (dotted lines) vessels. Both plots were normalized to the maximum PE-induced tension.
Mentions: First- and second-order mesenteric arteries, obtained from age-matched female non-operated control and ovariectomized (ovx; 4–6 weeks post ovariectomy; see Methods for details) mice, were mounted in an isometric wire myograph system. Following equilibration for at least 30 min at 37°C vessels were stretched to their optimal isometric initial resting tension of ∼2 mN and a stable baseline was established for at least 10 min before experimentation. Bath applications of phenylephrine (PE) contracted both control and ovx mesenteric arteries in a concentration-dependent manner (Fig. 1 left). Normalized concentration-response curves (Figure 1C) showed no significant differences in the overall sensitivity to PE between control and ovx mice (EC50 values: control 1.0±0.1 µM vs. 1.2±0.1 µM; n = 10). Following bath washout, the same vessels were pre-contracted with PE to induce ∼50% increase in tension (EC50), followed by bath applications of different concentrations of acetylcholine (ACh), and the concentration-response curves of ACh-induced vasorelaxation for these vessels were also established (Fig. 1 right). ACh-induced vasorelaxation was normalized to PE-induced contraction and fitted with sigmoidal curves for both control and ovx groups. Despite having similar IC50 values (control: 0.21±0.01 µM vs. ovx: 0.20±0.02 µM; n = 10), maximal ACh-induced vasorelaxation was reduced in vessels isolated from ovx animals (tension at 1 µM: control: 26.5% vs. ovx 46.9%; Fig. 1D).

Bottom Line: The results from functional studies using isolated murine mesenteric arteries show that ovx reduces ACh-induced endothelium-dependent vasodilation due to decreased EDH and NO contributions, although the contribution of PGI2 is upregulated.The decreased EDH-mediated vasorelaxation in ovx vessels is due to reduced SK3 channel contribution to the pathway.Further, whole-cell recordings using dispersed endothelial cells also show reduced SK3 current density in ovx endothelial cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, University of South Alabama, Mobile, Alabama, United States of America.

ABSTRACT
Mesenteric artery endothelium expresses both small (SK3)- and intermediate (IK1)-conductance Ca(2+)-activated K(+) (KCa) channels whose activity modulates vascular tone via endothelium-dependent hyperpolarization (EDH). Two other major endothelium-dependent vasodilation pathways utilize nitric oxide (NO) and prostacyclin (PGI2). To examine how ovariectomy (ovx) affects the basal activity and acetylcholine (ACh)-induced activity of each of these three pathways to vasorelaxation, we used wire myograph and electrophysiological recordings. The results from functional studies using isolated murine mesenteric arteries show that ovx reduces ACh-induced endothelium-dependent vasodilation due to decreased EDH and NO contributions, although the contribution of PGI2 is upregulated. Both endothelial SK3 and IK1 channels are functionally coupled to TRPV4 (transient receptor potential, vanilloid type 4) channels: the activation of TRPV4 channels activates SK3 and IK1 channels, leading to EDH-mediated vascular relaxation. The decreased EDH-mediated vasorelaxation in ovx vessels is due to reduced SK3 channel contribution to the pathway. Further, whole-cell recordings using dispersed endothelial cells also show reduced SK3 current density in ovx endothelial cells. Consequently, activation of TRPV4 channels induces smaller changes in whole-cell current density. Thus, ovariectomy leads to a reduction in endothelial SK3 channel activity thereby reducing the SK3 contribution to EDH vasorelaxation.

Show MeSH
Related in: MedlinePlus