Contractile recovery from acidosis in toad ventricle is independent of intracellular pH and relies upon Ca2+ influx

Hypercapnic acidosis produces a negative inotropic effect on myocardial contractility followed by a partial recovery that occurs in spite of the persistent extracellular acidosis. The underlying mechanisms of this recovery are far from understood, especially in those species in which excitation-cont...

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Autores principales: Salas, Margarita Ana, Vila Petroff, Martín Gerardo, Venosa, Roque, Mattiazzi, Alicia Ramona
Formato: Articulo
Lenguaje:Inglés
Publicado: 2006
Materias:
Ciencias Médicas
Acidosis
Buffo arenarum
Contracción Muscular
Sapo
Contracción Miocárdica
Acceso en línea:http://sedici.unlp.edu.ar/handle/10915/83509
Aporte de:
SEDICI (UNLP) de Universidad Nacional de La Plata
id I19-R120-10915-83509
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
Acidosis
Buffo arenarum
Contracción Muscular
Sapo
Contracción Miocárdica
spellingShingle Ciencias Médicas
Acidosis
Buffo arenarum
Contracción Muscular
Sapo
Contracción Miocárdica
Salas, Margarita Ana
Vila Petroff, Martín Gerardo
Venosa, Roque
Mattiazzi, Alicia Ramona
Contractile recovery from acidosis in toad ventricle is independent of intracellular pH and relies upon Ca2+ influx
topic_facet Ciencias Médicas
Acidosis
Buffo arenarum
Contracción Muscular
Sapo
Contracción Miocárdica
description Hypercapnic acidosis produces a negative inotropic effect on myocardial contractility followed by a partial recovery that occurs in spite of the persistent extracellular acidosis. The underlying mechanisms of this recovery are far from understood, especially in those species in which excitation-contraction coupling differs from that of the mammalian heart. The main goal of the present experiments was to obtain a better understanding of these mechanisms in the toad heart. Hypercapnic acidosis, induced by switching from a bicarbonate-buffered solution equilibrated with 5% CO2 to the same solution equilibrated with 12% CO2, evoked a decrease in contractility followed by a recovery that reached values higher than controls after 30 min of continued acidosis. This contractile pattern was associated with an initial decrease in intracellular pH (pHi) that recovered to control values in spite of the persistent extracellular acidosis. Blockade of the Na+/H+ exchanger (NHE) with cariporide (5 μmol l-1) produced a complete inhibition of pHi restitution, without affecting the mechanical recovery. Hypercapnic acidosis also produced a gradual increase of diastolic and peak Ca2+i transient values, which occurred immediately after the acidosis was settled and persisted during the mechanical recovery phase. Inhibition of Ca2+ influx through the reverse mode of the Na+/Ca2+ exchanger (NCX) by KB-R (1 μmol l-1 for myocytes and 20 μmol l-1 for ventricular strips), or of L-type Ca2+ channels by nifedipine (0.5 μmol l-1), completely abolished the mechanical recovery. Acidosis also produced an increase in the action potential duration. This prolongation persisted throughout the acidosis period. Our results show that in toad ventricular myocardium, acidosis produces a decrease in contractility, due to a decrease in Ca2+ myofilament responsiveness, followed by a contractile recovery, which is independent of pHi recovery and relies on an increase in the influx of Ca2+. The results further indicate that both the reverse mode NCX and the L-type Ca2+ channels, appear to be involved in the increase in intracellular Ca2+ concentration that mediates the contractile recovery from acidosis.
format Articulo
Articulo
author Salas, Margarita Ana
Vila Petroff, Martín Gerardo
Venosa, Roque
Mattiazzi, Alicia Ramona
author_facet Salas, Margarita Ana
Vila Petroff, Martín Gerardo
Venosa, Roque
Mattiazzi, Alicia Ramona
author_sort Salas, Margarita Ana
title Contractile recovery from acidosis in toad ventricle is independent of intracellular pH and relies upon Ca2+ influx
title_short Contractile recovery from acidosis in toad ventricle is independent of intracellular pH and relies upon Ca2+ influx
title_full Contractile recovery from acidosis in toad ventricle is independent of intracellular pH and relies upon Ca2+ influx
title_fullStr Contractile recovery from acidosis in toad ventricle is independent of intracellular pH and relies upon Ca2+ influx
title_full_unstemmed Contractile recovery from acidosis in toad ventricle is independent of intracellular pH and relies upon Ca2+ influx
title_sort contractile recovery from acidosis in toad ventricle is independent of intracellular ph and relies upon ca2+ influx
publishDate 2006
url http://sedici.unlp.edu.ar/handle/10915/83509
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