CIC   05421
CENTRO DE INVESTIGACIONES CARDIOVASCULARES "DR. HORACIO EUGENIO CINGOLANI"
Unidad Ejecutora - UE
artículos
Título:
The Electrogenic Na+/HCO3-Cotransport Modulates Resting Membrane Potential and Action Potential Duration in Cat Ventricular Myocytes
Autor/es:
MARIA C. VILLA-ABRILLE; VILA PETROFF, MARTÍN G; AIELLO, ERNESTO A
Revista:
THE JOURNAL OF PHYSIOLOGY
Referencias:
Año: 2007 vol. 578 p. 819 - 829
ISSN:
0022-3751
Resumen:
Perforated whole-cell configuration of patch clamp was used to determine the contribution of the electrogenic Na+/HCO3− cotransport (NBC) on the shape of the action potential in cat ventricular myocytes. Switching from Hepes to HCO3− buffer at constant extracellular pH (pHo) hyperpolarized resting membrane potential (RMP) by 2.67±0.42 mV (n=9, P <0.05). The duration of action potential measured at 50% of repolarization time (APD50) was 35.8±6.8% shorter in the presence of HCO3− than in its absence (n=9, P <0.05). The anion blocker SITS prevented and reversed the HCO3−-induced hyperpolarization and shortening of APD. In addition, no HCO3−-induced hyperpolarization and APD shortening was observed in the absence of extracellular Na+. Quasi-steady-state currents were evoked by 8 s duration voltage-clamped ramps ranging from −130 to +30 mV. A novel component of SITS-sensitive current was observed in the presence of HCO3−. The HCO3−-sensitive current reversed at−87±5mV(n=7), a value close tothe expectedreversalpotential of an electrogenic Na+/HCO3− cotransportwith aHCO3−:Na+ stoichiometry ratio of 2 : 1. The above results allow us to conclude that the cardiac electrogenicNa+/HCO3− cotransport has a relevant influence on RMP and APD of cat ventricular cells.+/HCO3− cotransport (NBC) on the shape of the action potential in cat ventricular myocytes. Switching from Hepes to HCO3− buffer at constant extracellular pH (pHo) hyperpolarized resting membrane potential (RMP) by 2.67±0.42 mV (n=9, P <0.05). The duration of action potential measured at 50% of repolarization time (APD50) was 35.8±6.8% shorter in the presence of HCO3− than in its absence (n=9, P <0.05). The anion blocker SITS prevented and reversed the HCO3−-induced hyperpolarization and shortening of APD. In addition, no HCO3−-induced hyperpolarization and APD shortening was observed in the absence of extracellular Na+. Quasi-steady-state currents were evoked by 8 s duration voltage-clamped ramps ranging from −130 to +30 mV. A novel component of SITS-sensitive current was observed in the presence of HCO3−. The HCO3−-sensitive current reversed at−87±5mV(n=7), a value close tothe expectedreversalpotential of an electrogenic Na+/HCO3− cotransportwith aHCO3−:Na+ stoichiometry ratio of 2 : 1. The above results allow us to conclude that the cardiac electrogenicNa+/HCO3− cotransport has a relevant influence on RMP and APD of cat ventricular cells.