Na+-Ca2+ exchange function underlying contraction frequency inotropy in the rat myocardium

In most mammalian species, an increase in stimulation frequency (ISF) produces an increase in contractility (treppe phenomenon), which results from larger Ca2+ transients at higher frequencies, due to an increase in sarcoplasmic reticulum Ca2+ load and release. The present study attempts to elucidat...

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Detalles Bibliográficos
Autores principales: Vila Petroff, Martín Gerardo, Palomeque, Julieta, Mattiazzi, Alicia Ramona
Formato: Articulo
Lenguaje:Inglés
Publicado: 2003
Materias:
Ciencias Médicas
Miocardio
Intercambiador de Sodio-Calcio
Acceso en línea:http://sedici.unlp.edu.ar/handle/10915/83262
Aporte de:
SEDICI (UNLP) de Universidad Nacional de La Plata
id I19-R120-10915-83262
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
Miocardio
Intercambiador de Sodio-Calcio
spellingShingle Ciencias Médicas
Miocardio
Intercambiador de Sodio-Calcio
Vila Petroff, Martín Gerardo
Palomeque, Julieta
Mattiazzi, Alicia Ramona
Na+-Ca2+ exchange function underlying contraction frequency inotropy in the rat myocardium
topic_facet Ciencias Médicas
Miocardio
Intercambiador de Sodio-Calcio
description In most mammalian species, an increase in stimulation frequency (ISF) produces an increase in contractility (treppe phenomenon), which results from larger Ca2+ transients at higher frequencies, due to an increase in sarcoplasmic reticulum Ca2+ load and release. The present study attempts to elucidate the contribution of the Na+-Ca2+ exchanger (NCX) to this phenomenon. Isolated cat ventricular myocytes, loaded with [Ca2+]i- and [Na+]i-sensitive probes, were used to determine whether the contribution of the NCX to the positive inotropic effect of ISF is due to an increase in Ca2+ influx (reverse mode) and/or a decrease in Ca2+ efflux (forward mode) via the NCX, due to frequency-induced [Na+]i elevation, or whether it was due to the reduced time for the NCX to extrude Ca2+. The results showed that the positive intropic effect produced by ISF was temporally dissociated from the increase in [Na+]i and was not modified by KB-R7943 (1 or 5 μM), a specific blocker of the reverse mode of the NCX. Whereas the ISF from 10 to 30 beats min-1 (bpm) did not affect the forward mode of the NCX (assessed by the time to half-relaxation of the caffeine-induced Ca2+ transient), the ISF to 50 bpm produced a significant reduction of the activity of the forward mode of the NCX, which occurred in association with an increase in [Na+]i (from 4.33 ± 0.40 to 7.25 ± 0.50 mM). However, both changes became significant well after the maximal positive inotropic effect had been reached. In contrast, the positive inotropic effect produced by ISF from 10 to 50 bpm was associated with an increase in diastolic [Ca2+]i, which occurred in spite of a significant increase in the relaxation rate and at a time at which no increases in [Na+]i were detected. The contribution of the NCX to stimulus frequency inotropy would therefore depend on a decrease in NCX-mediated Ca2+ efflux due to the reduced diastolic interval between beats and not on [Na+]i-dependent mechanisms.
format Articulo
Articulo
author Vila Petroff, Martín Gerardo
Palomeque, Julieta
Mattiazzi, Alicia Ramona
author_facet Vila Petroff, Martín Gerardo
Palomeque, Julieta
Mattiazzi, Alicia Ramona
author_sort Vila Petroff, Martín Gerardo
title Na+-Ca2+ exchange function underlying contraction frequency inotropy in the rat myocardium
title_short Na+-Ca2+ exchange function underlying contraction frequency inotropy in the rat myocardium
title_full Na+-Ca2+ exchange function underlying contraction frequency inotropy in the rat myocardium
title_fullStr Na+-Ca2+ exchange function underlying contraction frequency inotropy in the rat myocardium
title_full_unstemmed Na+-Ca2+ exchange function underlying contraction frequency inotropy in the rat myocardium
title_sort na+-ca2+ exchange function underlying contraction frequency inotropy in the rat myocardium
publishDate 2003
url http://sedici.unlp.edu.ar/handle/10915/83262
work_keys_str_mv AT vilapetroffmartingerardo naca2exchangefunctionunderlyingcontractionfrequencyinotropyintheratmyocardium
AT palomequejulieta naca2exchangefunctionunderlyingcontractionfrequencyinotropyintheratmyocardium
AT mattiazzialiciaramona naca2exchangefunctionunderlyingcontractionfrequencyinotropyintheratmyocardium
bdutipo_str Repositorios
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