Evidence for an electrogenic Na+-HCO<sub>3</sub>− symport in rat cardiac myocytes

1. The perforated whole-cell configuration of patch clamp and the pH fluorescent indicator SNARF were used to determine the electrogenicity of the Na+-HCO<sub>3</sub>- cotransport in isolated rat ventricular myocytes. 2. Switching from Hepes buffer to HCO<sub>3</sub>- buffer...

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Detalles Bibliográficos
Autores principales: Aiello, Ernesto Alejandro, Vila Petroff, Martín Gerardo, Mattiazzi, Alicia Ramona, Cingolani, Horacio Eugenio
Formato: Articulo
Lenguaje:Inglés
Publicado: 1998
Materias:
Ciencias Médicas
Hyperpolarization (biology)
Biophysics
Internal medicine
Endocrinology
Repolarization
Patch clamp
Membrane potential
Cotransporter
HEPES
Reversal potential
DIDS
Biology
Acceso en línea:http://sedici.unlp.edu.ar/handle/10915/122734
Aporte de:
SEDICI (UNLP) de Universidad Nacional de La Plata
id I19-R120-10915-122734
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
Hyperpolarization (biology)
Biophysics
Internal medicine
Endocrinology
Repolarization
Patch clamp
Membrane potential
Cotransporter
HEPES
Reversal potential
DIDS
Biology
spellingShingle Ciencias Médicas
Hyperpolarization (biology)
Biophysics
Internal medicine
Endocrinology
Repolarization
Patch clamp
Membrane potential
Cotransporter
HEPES
Reversal potential
DIDS
Biology
Aiello, Ernesto Alejandro
Vila Petroff, Martín Gerardo
Mattiazzi, Alicia Ramona
Cingolani, Horacio Eugenio
Evidence for an electrogenic Na+-HCO<sub>3</sub>− symport in rat cardiac myocytes
topic_facet Ciencias Médicas
Hyperpolarization (biology)
Biophysics
Internal medicine
Endocrinology
Repolarization
Patch clamp
Membrane potential
Cotransporter
HEPES
Reversal potential
DIDS
Biology
description 1. The perforated whole-cell configuration of patch clamp and the pH fluorescent indicator SNARF were used to determine the electrogenicity of the Na+-HCO<sub>3</sub>- cotransport in isolated rat ventricular myocytes. 2. Switching from Hepes buffer to HCO<sub>3</sub>- buffer at constant extracellular pH (pH<sub>o</sub>) hyperpolarized the resting membrane potential (RMP) by 2.9 +/- 0.4 mV (n = 9, P < 0.05). In the presence of HCO<sub>3</sub>-, the anion blocker SITS depolarized RMP by 2.6 +/- 0.5 mV (n = 5, P < 0.05). No HCO<sub>3</sub>--induced hyperpolarization was observed in the absence of extracellular Na+. The duration of the action potential measured at 50 % of repolarization time (APD<sub>50</sub>) was 29.2 +/- 6.1 % shorter in the presence of HCO<sub>3</sub>- than in its absence (n = 6, P < 0.05). 3. Quasi-steady-state currents were evoked by voltage-clamped ramps ranging from -130 to +30 mV, during 8 s. The development of a novel component of Na+-dependent and Cl--independent steady-state outward current was observed in the presence of HCO<sub>3</sub>-. The reversal potential (E<sub>rev</sub>) of the Na+-HCO<sub>3</sub>- cotransport current (I<sub>Na,Bic</sub>) was measured at four different levels of extracellular Na+. A HCO<sub>3</sub>-:Na+ ratio compatible with a stoichiometry of 2:1 was detected. I<sub>Na,Bic</sub> was also studied in isolation in standard whole-cell experiments. Under these conditions, I<sub>Na,Bic</sub> reversed at -96.4 +/- 1.9 mV (n = 5), being consistent with the influx of 2 HCO<sub>3</sub>- ions per Na+ ion through the Na+-HCO<sub>3</sub>- cotransporter. 4. In the presence of external HCO<sub>3</sub>-, after 10 min of depolarizing the membrane potential (Em) with 45 mM extracellular K+, a significant intracellular alkalinization was detected (0.09 +/- 0. 03 pH units; n = 5, P < 0.05). No changes in pHi were observed when the myocytes were pre-treated with the anion blocker DIDS (0.001 +/- 0.024 pH units; n = 5, n.s.), or when exposed to Na+-free solutions (0.003 +/- 0.037 pH units; n = 6, n.s.). 5. The above results allow us to conclude that the cardiac Na+-HCO<sub>3</sub>- cotransport is electrogenic and has an influence on RMP and APD of rat ventricular cells.
format Articulo
Articulo
author Aiello, Ernesto Alejandro
Vila Petroff, Martín Gerardo
Mattiazzi, Alicia Ramona
Cingolani, Horacio Eugenio
author_facet Aiello, Ernesto Alejandro
Vila Petroff, Martín Gerardo
Mattiazzi, Alicia Ramona
Cingolani, Horacio Eugenio
author_sort Aiello, Ernesto Alejandro
title Evidence for an electrogenic Na+-HCO<sub>3</sub>− symport in rat cardiac myocytes
title_short Evidence for an electrogenic Na+-HCO<sub>3</sub>− symport in rat cardiac myocytes
title_full Evidence for an electrogenic Na+-HCO<sub>3</sub>− symport in rat cardiac myocytes
title_fullStr Evidence for an electrogenic Na+-HCO<sub>3</sub>− symport in rat cardiac myocytes
title_full_unstemmed Evidence for an electrogenic Na+-HCO<sub>3</sub>− symport in rat cardiac myocytes
title_sort evidence for an electrogenic na+-hco<sub>3</sub>− symport in rat cardiac myocytes
publishDate 1998
url http://sedici.unlp.edu.ar/handle/10915/122734
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AT mattiazzialiciaramona evidenceforanelectrogenicnahcosub3subsymportinratcardiacmyocytes
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