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Angiotensin II Type 1 Receptor-Mediated Electrical Remodeling in Mouse Cardiac Myocytes.

Kim J, Gao J, Cohen IS, Mathias RT - PLoS ONE (2015)

Bottom Line: Pre-application of the microtubule destabilizing agent colchicine eliminated A2 effects on Ito and AP duration, suggesting these effects depend on intracellular trafficking.Application of the biased agonist SII ([Sar1-Ile4-Ile8]A2), which stimulates receptor internalization without G protein activation, caused Ito reduction and AP prolongation similar to A2-induced changes.Moreover, all measured properties parallel those measured in dog heart, suggesting an autocrine RAS may be a fundamental feedback system that is present across species.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology & Biophysics, State University of New York at Stony Brook, Stony Brook, New York, United States of America.

ABSTRACT
We recently characterized an autocrine renin angiotensin system (RAS) in canine heart. Activation of Angiotensin II Type 1 Receptors (AT1Rs) induced electrical remodeling, including inhibition of the transient outward potassium current Ito, prolongation of the action potential (AP), increased calcium entry and increased contractility. Electrical properties of the mouse heart are very different from those of dog heart, but if a similar system existed in mouse, it could be uniquely studied through genetic manipulations. To investigate the presence of a RAS in mouse, we measured APs and Ito in isolated myocytes. Application of angiotensin II (A2) for 2 or more hours reduced Ito magnitude, without affecting voltage dependence, and prolonged APs in a dose-dependent manner. Based on dose-inhibition curves, the fast and slow components of Ito (Ito,fast and IK,slow) appeared to be coherently regulated by [A2], with 50% inhibition at an A2 concentration of about 400 nM. This very high K0.5 is inconsistent with systemic A2 effects, but is consistent with an autocrine RAS in mouse heart. Pre-application of the microtubule destabilizing agent colchicine eliminated A2 effects on Ito and AP duration, suggesting these effects depend on intracellular trafficking. Application of the biased agonist SII ([Sar1-Ile4-Ile8]A2), which stimulates receptor internalization without G protein activation, caused Ito reduction and AP prolongation similar to A2-induced changes. These data demonstrate AT1R mediated regulation of Ito in mouse heart. Moreover, all measured properties parallel those measured in dog heart, suggesting an autocrine RAS may be a fundamental feedback system that is present across species.

No MeSH data available.


Related in: MedlinePlus

Dose dependence of A2 induced AP prolongation.(A) Representative AP waveforms measured from LV myocytes incubated in the presence of zero, 100 nM and 5 μM A2. (B) APs display A2 dose-dependent prolongation of early (APD50) and late (APD90) repolarization. Based on a Regression Analysis, increasing concentrations of A2 caused increases in APDs (P = 0.015). (C) A2 stimulated cells exhibit no significant changes in resting potential, Vrest. (D) Peak AP voltage, Vpeak, is also not significantly affected by A2.
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pone.0138711.g001: Dose dependence of A2 induced AP prolongation.(A) Representative AP waveforms measured from LV myocytes incubated in the presence of zero, 100 nM and 5 μM A2. (B) APs display A2 dose-dependent prolongation of early (APD50) and late (APD90) repolarization. Based on a Regression Analysis, increasing concentrations of A2 caused increases in APDs (P = 0.015). (C) A2 stimulated cells exhibit no significant changes in resting potential, Vrest. (D) Peak AP voltage, Vpeak, is also not significantly affected by A2.

Mentions: Fig 1A presents representative AP recordings from control (CON) myocytes and from myocytes incubated with A2. The myocytes displayed A2 concentration-dependent prolongation in AP duration. Early and late phase repolarizations (APD50 and APD90, respectively) increase with an increased dose of externally applied A2 (Fig 1B). APD50 values were 3.82 ± 0.30 ms (CON, n = 20), 5.19 ± 0.76 ms (100 nM A2, n = 19) and 6.61 ± 1.08 ms (5 μM A2, n = 22). A similar trend in APD90 was observed as well: 16.21 ± 1.17 ms (CON), 21.18 ± 2.63 ms (100 nM A2) and 25.37 ± 3.28 ms (5 μM A2). A2 caused no changes in either the resting potential, Vrest (Fig 1C) or the peak potential, Vpeak (Fig 1D). The data indicate A2 stimulation in LV myocytes triggers the remodeling of one or more membrane currents that significantly contribute to action potential repolarization.


Angiotensin II Type 1 Receptor-Mediated Electrical Remodeling in Mouse Cardiac Myocytes.

Kim J, Gao J, Cohen IS, Mathias RT - PLoS ONE (2015)

Dose dependence of A2 induced AP prolongation.(A) Representative AP waveforms measured from LV myocytes incubated in the presence of zero, 100 nM and 5 μM A2. (B) APs display A2 dose-dependent prolongation of early (APD50) and late (APD90) repolarization. Based on a Regression Analysis, increasing concentrations of A2 caused increases in APDs (P = 0.015). (C) A2 stimulated cells exhibit no significant changes in resting potential, Vrest. (D) Peak AP voltage, Vpeak, is also not significantly affected by A2.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4591968&req=5

pone.0138711.g001: Dose dependence of A2 induced AP prolongation.(A) Representative AP waveforms measured from LV myocytes incubated in the presence of zero, 100 nM and 5 μM A2. (B) APs display A2 dose-dependent prolongation of early (APD50) and late (APD90) repolarization. Based on a Regression Analysis, increasing concentrations of A2 caused increases in APDs (P = 0.015). (C) A2 stimulated cells exhibit no significant changes in resting potential, Vrest. (D) Peak AP voltage, Vpeak, is also not significantly affected by A2.
Mentions: Fig 1A presents representative AP recordings from control (CON) myocytes and from myocytes incubated with A2. The myocytes displayed A2 concentration-dependent prolongation in AP duration. Early and late phase repolarizations (APD50 and APD90, respectively) increase with an increased dose of externally applied A2 (Fig 1B). APD50 values were 3.82 ± 0.30 ms (CON, n = 20), 5.19 ± 0.76 ms (100 nM A2, n = 19) and 6.61 ± 1.08 ms (5 μM A2, n = 22). A similar trend in APD90 was observed as well: 16.21 ± 1.17 ms (CON), 21.18 ± 2.63 ms (100 nM A2) and 25.37 ± 3.28 ms (5 μM A2). A2 caused no changes in either the resting potential, Vrest (Fig 1C) or the peak potential, Vpeak (Fig 1D). The data indicate A2 stimulation in LV myocytes triggers the remodeling of one or more membrane currents that significantly contribute to action potential repolarization.

Bottom Line: Pre-application of the microtubule destabilizing agent colchicine eliminated A2 effects on Ito and AP duration, suggesting these effects depend on intracellular trafficking.Application of the biased agonist SII ([Sar1-Ile4-Ile8]A2), which stimulates receptor internalization without G protein activation, caused Ito reduction and AP prolongation similar to A2-induced changes.Moreover, all measured properties parallel those measured in dog heart, suggesting an autocrine RAS may be a fundamental feedback system that is present across species.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology & Biophysics, State University of New York at Stony Brook, Stony Brook, New York, United States of America.

ABSTRACT
We recently characterized an autocrine renin angiotensin system (RAS) in canine heart. Activation of Angiotensin II Type 1 Receptors (AT1Rs) induced electrical remodeling, including inhibition of the transient outward potassium current Ito, prolongation of the action potential (AP), increased calcium entry and increased contractility. Electrical properties of the mouse heart are very different from those of dog heart, but if a similar system existed in mouse, it could be uniquely studied through genetic manipulations. To investigate the presence of a RAS in mouse, we measured APs and Ito in isolated myocytes. Application of angiotensin II (A2) for 2 or more hours reduced Ito magnitude, without affecting voltage dependence, and prolonged APs in a dose-dependent manner. Based on dose-inhibition curves, the fast and slow components of Ito (Ito,fast and IK,slow) appeared to be coherently regulated by [A2], with 50% inhibition at an A2 concentration of about 400 nM. This very high K0.5 is inconsistent with systemic A2 effects, but is consistent with an autocrine RAS in mouse heart. Pre-application of the microtubule destabilizing agent colchicine eliminated A2 effects on Ito and AP duration, suggesting these effects depend on intracellular trafficking. Application of the biased agonist SII ([Sar1-Ile4-Ile8]A2), which stimulates receptor internalization without G protein activation, caused Ito reduction and AP prolongation similar to A2-induced changes. These data demonstrate AT1R mediated regulation of Ito in mouse heart. Moreover, all measured properties parallel those measured in dog heart, suggesting an autocrine RAS may be a fundamental feedback system that is present across species.

No MeSH data available.


Related in: MedlinePlus