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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

A2 induced reductions in Ito,fast and IK,slow.(A) Representative traces of total outward K+-currents recorded from untreated (CON) LV myocytes and those treated with 5 μM. Outward currents were elicited with 6 s test potentials ranging from -10 mV to +50 mV from a holding potential of -65 mV with a 10 ms prepulse to -30 mV to inactivate the fast Na+ current, as shown in the inset. Voltage dependences of peak Ito,fast(B) and IK,slow(C) densities were determined by curve fitting two exponentials to the recorded current traces. Based on ANOVA statistical analyses, the overall responses differ significantly (Ito,fast P = 0.005, and IK,slow P = 0.001). Post hoc statistical analyses of A2 induced changes at each voltage were all significant (P < 0.05).
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pone.0138711.g002: A2 induced reductions in Ito,fast and IK,slow.(A) Representative traces of total outward K+-currents recorded from untreated (CON) LV myocytes and those treated with 5 μM. Outward currents were elicited with 6 s test potentials ranging from -10 mV to +50 mV from a holding potential of -65 mV with a 10 ms prepulse to -30 mV to inactivate the fast Na+ current, as shown in the inset. Voltage dependences of peak Ito,fast(B) and IK,slow(C) densities were determined by curve fitting two exponentials to the recorded current traces. Based on ANOVA statistical analyses, the overall responses differ significantly (Ito,fast P = 0.005, and IK,slow P = 0.001). Post hoc statistical analyses of A2 induced changes at each voltage were all significant (P < 0.05).

Mentions: Voltage clamp recordings obtained from LV cells incubated with 5 μM A2 were compared with recordings measured in CON cells. Fig 2A presents representative traces of the total outward current in CON and 5 μM A2 cells. The voltage clamp protocol showed in the inset to Fig 2A caused a rapid, transient increase in the outward current that was consistent with K+ currents that have been described previously in mouse left ventricular myocytes [29]. Ito,fast and IK,slow were separated from these traces by fitting exponential functions to the data as described in Materials and Methods. Peak current densities at each test potential were averaged and plotted as a function of the test potential (Vtest). Peak Ito,fast and IK,slow current-voltage relationships obtained from CON vs 5 μM A2 cells are presented in Fig 2B and 2C.


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

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

A2 induced reductions in Ito,fast and IK,slow.(A) Representative traces of total outward K+-currents recorded from untreated (CON) LV myocytes and those treated with 5 μM. Outward currents were elicited with 6 s test potentials ranging from -10 mV to +50 mV from a holding potential of -65 mV with a 10 ms prepulse to -30 mV to inactivate the fast Na+ current, as shown in the inset. Voltage dependences of peak Ito,fast(B) and IK,slow(C) densities were determined by curve fitting two exponentials to the recorded current traces. Based on ANOVA statistical analyses, the overall responses differ significantly (Ito,fast P = 0.005, and IK,slow P = 0.001). Post hoc statistical analyses of A2 induced changes at each voltage were all significant (P < 0.05).
© Copyright Policy
Related In: Results  -  Collection

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

pone.0138711.g002: A2 induced reductions in Ito,fast and IK,slow.(A) Representative traces of total outward K+-currents recorded from untreated (CON) LV myocytes and those treated with 5 μM. Outward currents were elicited with 6 s test potentials ranging from -10 mV to +50 mV from a holding potential of -65 mV with a 10 ms prepulse to -30 mV to inactivate the fast Na+ current, as shown in the inset. Voltage dependences of peak Ito,fast(B) and IK,slow(C) densities were determined by curve fitting two exponentials to the recorded current traces. Based on ANOVA statistical analyses, the overall responses differ significantly (Ito,fast P = 0.005, and IK,slow P = 0.001). Post hoc statistical analyses of A2 induced changes at each voltage were all significant (P < 0.05).
Mentions: Voltage clamp recordings obtained from LV cells incubated with 5 μM A2 were compared with recordings measured in CON cells. Fig 2A presents representative traces of the total outward current in CON and 5 μM A2 cells. The voltage clamp protocol showed in the inset to Fig 2A caused a rapid, transient increase in the outward current that was consistent with K+ currents that have been described previously in mouse left ventricular myocytes [29]. Ito,fast and IK,slow were separated from these traces by fitting exponential functions to the data as described in Materials and Methods. Peak current densities at each test potential were averaged and plotted as a function of the test potential (Vtest). Peak Ito,fast and IK,slow current-voltage relationships obtained from CON vs 5 μM A2 cells are presented in Fig 2B and 2C.

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