Angiotensin II Activates Na+-Independent Cl−-HCO3− Exchange in Ventricular Myocardium

The effect of angiotensin II (Ang II) on the activity of the cardiac Na+-independent Cl−-HCO3− exchanger (anionic exchanger [AE]) was explored in cat papillary muscles. pHi was measured by epifluorescence with BCECF-AM. Ang II (500 nmol/L) induced a 5-( N -ethyl- N -isopropyl)amiloride–sensitive inc...

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Autores principales: Camilión de Hurtado, María Cristina, Álvarez, Bernardo Víctor, Pérez, Néstor Gustavo, Ennis, Irene Lucía, Cingolani, Horacio Eugenio
Formato: Articulo
Lenguaje:Inglés
Publicado: 1998
Materias:
Acceso en línea:http://sedici.unlp.edu.ar/handle/10915/146787
Aporte de:
id I19-R120-10915-146787
record_format dspace
institution Universidad Nacional de La Plata
institution_str I-19
repository_str R-120
collection SEDICI (UNLP)
language Inglés
topic Ciencias Médicas
Na1-independent Cl2-HCO3 2 exchanger n
AT1 receptor n
angiotensin II
myocardial pH
protein kinase C
spellingShingle Ciencias Médicas
Na1-independent Cl2-HCO3 2 exchanger n
AT1 receptor n
angiotensin II
myocardial pH
protein kinase C
Camilión de Hurtado, María Cristina
Álvarez, Bernardo Víctor
Pérez, Néstor Gustavo
Ennis, Irene Lucía
Cingolani, Horacio Eugenio
Angiotensin II Activates Na+-Independent Cl−-HCO3− Exchange in Ventricular Myocardium
topic_facet Ciencias Médicas
Na1-independent Cl2-HCO3 2 exchanger n
AT1 receptor n
angiotensin II
myocardial pH
protein kinase C
description The effect of angiotensin II (Ang II) on the activity of the cardiac Na+-independent Cl−-HCO3− exchanger (anionic exchanger [AE]) was explored in cat papillary muscles. pHi was measured by epifluorescence with BCECF-AM. Ang II (500 nmol/L) induced a 5-( N -ethyl- N -isopropyl)amiloride–sensitive increase in pHi in the absence of external HCO3− (HEPES buffer), consistent with its stimulatory action on Na+-H+ exchange (NHE). This alkalinizing effect was not detected in the presence of a CO2-HCO3− buffer (pHi 7.07±0.02 and 7.08±0.02 before and after Ang II, respectively; n=17). Moreover, in Na+-free HCO3−–buffered medium, in which neither NHE nor Na+-HCO3− cotransport are acting, Ang II decreased pHi, and this effect was canceled by previous treatment with SITS. These findings suggested that the Ang II–induced activation of NHE was masked, in the presence of the physiological buffer, by a HCO3−-dependent acidifying mechanism, probably the AE. This hypothesis was confirmed on papillary muscles bathed with HCO3− buffer that were first exposed to 1 μmol/L S20787, a specific inhibitor of AE activity in cardiac tissue, and then to 500 nmol/L Ang II (n=4). Under this condition, Ang II increased pHi from 7.05±0.05 to 7.22±0.05 ( P <.05). The effect of Ang II on AE activity was further explored by measuring the velocity of myocardial pHi recovery after the imposition of an intracellular alkali load in a HCO3−-containing solution either with or without Ang II. The rate of myocardial pHi recovery was doubled in the presence of Ang II, suggesting a stimulatory effect on AE. The enhancement of the activity of this exchanger by Ang II was also detected when the AE activity was reversed by the removal of extracellular Cl− in a Na+-free solution. Under this condition, the rate of intracellular alkalinization increased from 0.053±0.016 to 0.108±0.026 pH unit/min (n=6, P <.05) in the presence of Ang II. This effect was canceled either by the presence of the AT1 receptor antagonist, losartan, or by the previous inhibition of protein kinase C with chelerythrine or calphostin C. The above results allow us to conclude that Ang II, in addition to its stimulatory effect on alkaline loading mechanisms, activates the AE in ventricular myocardium and that the latter effect is mediated by a protein kinase C–dependent regulatory pathway linked to the AT1 receptors.
format Articulo
Articulo
author Camilión de Hurtado, María Cristina
Álvarez, Bernardo Víctor
Pérez, Néstor Gustavo
Ennis, Irene Lucía
Cingolani, Horacio Eugenio
author_facet Camilión de Hurtado, María Cristina
Álvarez, Bernardo Víctor
Pérez, Néstor Gustavo
Ennis, Irene Lucía
Cingolani, Horacio Eugenio
author_sort Camilión de Hurtado, María Cristina
title Angiotensin II Activates Na+-Independent Cl−-HCO3− Exchange in Ventricular Myocardium
title_short Angiotensin II Activates Na+-Independent Cl−-HCO3− Exchange in Ventricular Myocardium
title_full Angiotensin II Activates Na+-Independent Cl−-HCO3− Exchange in Ventricular Myocardium
title_fullStr Angiotensin II Activates Na+-Independent Cl−-HCO3− Exchange in Ventricular Myocardium
title_full_unstemmed Angiotensin II Activates Na+-Independent Cl−-HCO3− Exchange in Ventricular Myocardium
title_sort angiotensin ii activates na+-independent cl−-hco3− exchange in ventricular myocardium
publishDate 1998
url http://sedici.unlp.edu.ar/handle/10915/146787
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