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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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Compromised ACh-induced relaxation in ovx mesenteric vessels.A: Representative force myograph traces showing isometric tension (mN) plotted against the time of recording (s) using control (top panel) and ovx (bottom panel) mesenteric vessels. Bath application of PE (3 and 5 µM) induced vasoconstriction, ACh (1 µM) induced vasorelaxation, was followed by bath solution replacement with physiological salt solution containing 60 mM KCl that induced vasoconstriction. B: Summary of isometric tension changes induced by PE (3 uM), KCl, and ACh for both control (black) and ovx (grey) vessels. Negative values show vasorelaxation. C: Tension changes normalized to the KCl-induced contraction for both PE and ACh. Ovx vessels show reduced ACh response. Asterisk (*) denotes statistical significance (P<0.05, t-test).
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pone-0104686-g002: Compromised ACh-induced relaxation in ovx mesenteric vessels.A: Representative force myograph traces showing isometric tension (mN) plotted against the time of recording (s) using control (top panel) and ovx (bottom panel) mesenteric vessels. Bath application of PE (3 and 5 µM) induced vasoconstriction, ACh (1 µM) induced vasorelaxation, was followed by bath solution replacement with physiological salt solution containing 60 mM KCl that induced vasoconstriction. B: Summary of isometric tension changes induced by PE (3 uM), KCl, and ACh for both control (black) and ovx (grey) vessels. Negative values show vasorelaxation. C: Tension changes normalized to the KCl-induced contraction for both PE and ACh. Ovx vessels show reduced ACh response. Asterisk (*) denotes statistical significance (P<0.05, t-test).

Mentions: To further characterize the contractility difference in control and ovx vessels, in a different set of experiments we quantified the effect of both PE- and ACh-induced changes in vascular tension and normalized them to the maximal tension induced with high [K+]o. Bath applied PE increased the isometric tensions in both control and ovx mesenteric arteries to a similar extent (3 µM PE: control: 2.3±0.2 mN, n = 9; ovx: 2.8±0.3 mN; n = 8; P>0.05; Fig. 2A and B). Subsequent bath applied 1 µM ACh reduced vascular tension was more pronounced in control vessels (1.9±0.2 mN, n = 9) than in ovx vessels (1.1±0.1 mN, n = 8; P<0.05), consistent with a reduced maximal ACh-induced vasorelaxation in ovx vessels (Fig. 1D). Next, bath solution was then replaced with a PSS containing high KCl (increased by 60 mM with 1∶1 KCl:NaCl replacement), which depolarizes smooth muscle cell membrane potential and activates voltage-dependent L-type Ca2+ channels, resulting in maximally increased vascular tension in both groups of vessels (control: 2.7±0.2 mN, n = 9; ovx: 3.8±0.5 mN, n = 8; P>0.05; Fig. 2A and B). KCl-induced contraction was comparable to the maximal tension induced with high [PE] and was used to normalize the vasoactive effects of PE and ACh. Figure 2C shows the changes in tension, normalized to KCl-induced contraction, for both PE-induced contraction and ACh-induced relaxation. PE-induced vasoconstriction was similar in mesenteric arteries isolated from both control and ovx groups; however, ACh-induced vasorelaxation was reduced in ovx arteries (control: 67±6%, n = 9; ovx: 35±9%, n = 8; P<0.05), indicating differential ACh-induced endothelium-dependent vasorelaxation between these two animal groups.


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)

Compromised ACh-induced relaxation in ovx mesenteric vessels.A: Representative force myograph traces showing isometric tension (mN) plotted against the time of recording (s) using control (top panel) and ovx (bottom panel) mesenteric vessels. Bath application of PE (3 and 5 µM) induced vasoconstriction, ACh (1 µM) induced vasorelaxation, was followed by bath solution replacement with physiological salt solution containing 60 mM KCl that induced vasoconstriction. B: Summary of isometric tension changes induced by PE (3 uM), KCl, and ACh for both control (black) and ovx (grey) vessels. Negative values show vasorelaxation. C: Tension changes normalized to the KCl-induced contraction for both PE and ACh. Ovx vessels show reduced ACh response. Asterisk (*) denotes statistical significance (P<0.05, t-test).
© Copyright Policy
Related In: Results  -  Collection

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

pone-0104686-g002: Compromised ACh-induced relaxation in ovx mesenteric vessels.A: Representative force myograph traces showing isometric tension (mN) plotted against the time of recording (s) using control (top panel) and ovx (bottom panel) mesenteric vessels. Bath application of PE (3 and 5 µM) induced vasoconstriction, ACh (1 µM) induced vasorelaxation, was followed by bath solution replacement with physiological salt solution containing 60 mM KCl that induced vasoconstriction. B: Summary of isometric tension changes induced by PE (3 uM), KCl, and ACh for both control (black) and ovx (grey) vessels. Negative values show vasorelaxation. C: Tension changes normalized to the KCl-induced contraction for both PE and ACh. Ovx vessels show reduced ACh response. Asterisk (*) denotes statistical significance (P<0.05, t-test).
Mentions: To further characterize the contractility difference in control and ovx vessels, in a different set of experiments we quantified the effect of both PE- and ACh-induced changes in vascular tension and normalized them to the maximal tension induced with high [K+]o. Bath applied PE increased the isometric tensions in both control and ovx mesenteric arteries to a similar extent (3 µM PE: control: 2.3±0.2 mN, n = 9; ovx: 2.8±0.3 mN; n = 8; P>0.05; Fig. 2A and B). Subsequent bath applied 1 µM ACh reduced vascular tension was more pronounced in control vessels (1.9±0.2 mN, n = 9) than in ovx vessels (1.1±0.1 mN, n = 8; P<0.05), consistent with a reduced maximal ACh-induced vasorelaxation in ovx vessels (Fig. 1D). Next, bath solution was then replaced with a PSS containing high KCl (increased by 60 mM with 1∶1 KCl:NaCl replacement), which depolarizes smooth muscle cell membrane potential and activates voltage-dependent L-type Ca2+ channels, resulting in maximally increased vascular tension in both groups of vessels (control: 2.7±0.2 mN, n = 9; ovx: 3.8±0.5 mN, n = 8; P>0.05; Fig. 2A and B). KCl-induced contraction was comparable to the maximal tension induced with high [PE] and was used to normalize the vasoactive effects of PE and ACh. Figure 2C shows the changes in tension, normalized to KCl-induced contraction, for both PE-induced contraction and ACh-induced relaxation. PE-induced vasoconstriction was similar in mesenteric arteries isolated from both control and ovx groups; however, ACh-induced vasorelaxation was reduced in ovx arteries (control: 67±6%, n = 9; ovx: 35±9%, n = 8; P<0.05), indicating differential ACh-induced endothelium-dependent vasorelaxation between these two animal groups.

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