Membrane stretch evoked by cell swelling increases contractile activity in vascular smooth muscle through dihydropyridine-sensitive pathways

Vascular smooth muscle cells (VSMCs) can regulate arterial mechanics via contractile activity in response to changing mechanical and chemical signals. Contractility is traditionally evaluated via uniaxial isometric testing of isolated rings despite the in vivo environment being very different. Most blood vessels maintain a locally preferred value of in vivo axial stretch while subjected to changes in distending pressure, but both of these phenomena are obscured in uniaxial isometric testing. Few studies have rigorously analyzed the role of in vivo loading conditions in smooth muscle function. Thus, we evaluated effects of uniaxial versus biaxial deformations on smooth muscle contractility by stimulating two regions of the mouse aorta with different vasoconstrictors using one of three testing protocols: (i) uniaxial isometric testing, (ii) biaxial isometric testing, and (iii) axially isometric plus isobaric testing. Comparison of methods (i) and (ii) revealed increased sensitivity and contractile capacity to potassium chloride and phenylephrine (PE) with biaxial isometric testing, and comparison of methods (ii) and (iii) revealed a further increase in contractile capacity with isometric plus isobaric testing. Importantly, regional differences in estimated in vivo axial stretch suggest locally distinct optimal biaxial configurations for achieving maximal smooth muscle contraction, which can only be revealed with biaxial testing. Such differences highlight the importance of considering in vivo loading and geometric configurations when evaluating smooth muscle function. Given the physiologic relevance of axial extension and luminal pressurization, we submit that, when possible, axially isometric plus isobaric testing should be employed to evaluate vascular smooth muscle contractile function.

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Darusentan is a potent inhibitor of endothelin signaling and function in both large and small arteriesThis article is one of a selection of papers published in the two-part special issue entitled 20 Years of Endothelin Research.

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y10-061 ◽

2010 ◽

Vol 88 (8) ◽

pp. 840-849 ◽

Cited By ~ 3

Author(s):

Faquan Liang ◽

Christopher B. Glascock ◽

Denise L. Schafer ◽

Jennifer Sandoval ◽

LouAnn Cable ◽

...

Keyword(s):

Smooth Muscle ◽

Vascular Smooth Muscle ◽

Potent Inhibitor ◽

Inositol Phosphate ◽

Contractile Activity ◽

Binding Activity ◽

Dependent Manner ◽

Endothelin Receptor ◽

Resistance Arteries ◽

Concentration Dependent Manner

Endothelin is a potent vasoconstrictor often up-regulated in hypertension. Endothelin vasoconstriction is mediated via the G-protein coupled endothelin A (ETA) receptor present on vascular smooth muscle. Endothelin receptor antagonists (ERAs) have been shown to antagonize ET-induced vasoconstriction. We describe the primary pharmacology of darusentan, a propanoic acid based ERA currently in phase 3 clinical trials for resistant hypertension. Darusentan was tested in membrane-, cell-, and tissue-based assays to determine its biochemical and functional potency. Rat aortic vascular smooth muscle cells (RAVSMs) were characterized using flow cytometry. RAVSM membrane fractions tested in saturation experiments exhibited moderate endothelin receptor density. Receptor counting revealed that >95% of the endothelin receptors in these fractions were the ETA subtype. (S)-Darusentan competed for radiolabeled endothelin binding in RAVSM membranes with single-site kinetics, exhibiting a Ki = 13 nmol/L. (R)-Darusentan exhibited no binding activity. In cultured RAVSMs, endothelin induced increases in inositol phosphate and Ca2+ signaling, both of which were attenuated by (S)-darusentan in a concentration-dependent manner. In isolated endothelium-denuded rat aortic rings, (S)-darusentan inhibited endothelin-induced vascular contractility with a pA2 = 8.1 ± 0.14 (n = 4 animals; mean ± SD). (R)-Darusentan had no effect. The vasorelaxant potency of (S)-darusentan did not change when determined in isolated denuded rat mesenteric arterioles, suggesting a similar mode of action in both conductance and resistance arteries. In vascular smooth muscle, (S)-darusentan is an ERA with high affinity for the ET receptor, which in this preparation is predominantly ETA receptors. (S)-Darusentan inhibits endothelin-induced signaling related to pro-contractile activity and is a potent inhibitor of vasoconstriction in large and small arteries.

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Effect of hydrogen sulfide on the contractile activity of smooth muscle cells from the rat aorta

Bulletin of Siberian Medicine ◽

10.20538/1682-0363-2010-6-12-17 ◽

2010 ◽

Vol 9 (6) ◽

pp. 12-17

Author(s):

M. B. Baskakov ◽

S. V. Gusakova ◽

A. S. Zheludeva ◽

L. V. Smagly ◽

I. V. Kovalyov ◽

...

Keyword(s):

Smooth Muscle ◽

Hydrogen Sulfide ◽

Vascular Smooth Muscle ◽

Smooth Muscle Cells ◽

Contractile Activity ◽

Muscle Cells ◽

Rat Aorta ◽

Mechanisms Of Action ◽

High K ◽

Lower Amplitude

In preparations of rat aorta, used as a model of muscular type arteries, the method mehanografii studied the effect of hydrogen sulfide on the reduction of isolated of vascular smooth muscle. Found that hydrogen sulfide in concentrations 1—50 mmol increases the mechanical stress of smooth muscle in high-K + medium. At higher concentrations (300—1 000 mmol) H2S leads to lower amplitude giperkalievoy contraction in high-K + medium. Reduction of smooth muscle cells caused by phenylephrine inhibited the action of hydrogen sulfide in the whole range of concentrations. The causes of differences in data obtained with the results of studies in other laboratories, and possible mechanisms of action of hydrogen sulfide on the contractile activity of vascular smooth muscle.

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Both membrane stretch and fatty acids directly activate large conductance Ca2+ -activated K+ channels in vascular smooth muscle cells

FEBS Letters ◽

10.1016/0014-5793(92)80319-c ◽

1992 ◽

Vol 297 (1-2) ◽

pp. 24-28 ◽

Cited By ~ 150

Author(s):

Michael T. Kirber ◽

Richard W. Ordway ◽

Lucie H. Clapp ◽

John V. Walsh ◽

Joshua J. Singer

Keyword(s):

Fatty Acids ◽

Smooth Muscle ◽

Vascular Smooth Muscle ◽

Smooth Muscle Cells ◽

Vascular Smooth Muscle Cells ◽

Muscle Cells ◽

K Channels ◽

Membrane Stretch

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Heightened Vascular Reactivity Following Sympathetic Denervation Correlates with Increased Expression of C-Kit and Connexin43

Hypertension ◽

10.1161/hyp.36.suppl_1.706 ◽

2000 ◽

Vol 36 (suppl_1) ◽

pp. 706-706

Author(s):

David Paul Slovut ◽

Anne N Dorrance ◽

Frank C Brosius ◽

Stephanie W Watts ◽

R. Clinton Webb

Keyword(s):

Smooth Muscle ◽

Vascular Smooth Muscle ◽

Vascular Reactivity ◽

Contractile Activity ◽

Sympathetic Denervation ◽

Oscillatory Activity ◽

Maximal Response ◽

Mrna Levels ◽

Pacemaker Cells ◽

Cx43 Expression

P71 Short-term denervation produces supersensitivity to α-adrenergic agonists that resembles the heightened vascular reactivity observed in hypertensive subjects. Gap junctions, transmembrane channels responsible for cell-to-cell communication, may play a role in maintaining increased vascular reactivity. We examined the effects of denervation with intra-peritoneal reserpine 3 mg/kg/day (N=5) or topical 5% phenol-glycerol (N=7) on agonist-induced oscillatory activity. Wistar-Kyoto (WKY) rat tail arteries were exposed to step-wise addition of norepinephrine (NE) 10 -9 M-10 -5 M. The concentration for half-maximal response for NE-induced contraction was lower in reserpine- and phenol-treated vessels than controls (log EC 50 [mol]/L control -6.89 vs reserpine -7.16, p<0.05); control -6.86 vs phenol -7.32, p<0.0001). Incubation in K + -free solution produced an 8-fold increase in isometric tension in control vs denervated vessels (138.4±23.2 vs 17.2±4.5 % of contraction to phenylephrine 10 -6 M, p<0.001). These findings are consistent with adrenergic denervation. Agonist-induced oscillatory activity was observed in 5/5 reserpine- and 4/7 phenol-treated vessels vs 0/12 controls (Fischer’s exact test p<0.05). The highly selective gap junction inhibitor, Gap27 (10 mM), nearly abolished NE-induced vascular smooth muscle oscillations. Reverse transcriptase polymerase chain reaction was carried out for connexin43 (Cx43) and c-Kit, a marker for non-neural interstitial cells that serve as pacemaker cells, using specific oligonucleotide primers. Following denervation, mRNA levels of Cx43 remained unchanged while levels of c-Kit increased markedly (0.16±0.03 vs 0.62±0.13 a.u., p<0.05). Western blot analysis revealed near doubling of Cx43 protein after denervation (80.0±13.7 vs 41.4±5.7 a.u., p<0.05). In conclusion, sympathetic denervation produced increased agonist-induced oscillatory contractile activity in vascular smooth muscle. The heightened vascular reactivity may result from upregulation of pacemaker cells and increased Cx43 expression.

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