The role of aging on the control of contractile force by Na+-Ca2+ exchange in rat papillary muscle

Pasquale Abete, Nicola Ferrara, Angelo Cioppa

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Abstract

Background. Sarcolemmal Na+-Ca2+ exchange system is believed to be fundamental to the control of cardiac contractility. However, the relation between Na+-Ca2+ exchange and the control of contractile force has not been studied in senescent myocardium. Methods. The role of Na+-Ca2+ exchange in the regulation of the cardiac muscle's contractile force was studied in adult and senescent papillary muscles by simultaneously measuring intracellular sodium activity (a'Nl), action potential, and contractile force while varying extracellular concentration of sodium and/or calcium. Results. Reductionof[Na+]0decreaseda'Nlfrom8.0 ±1.8to4.1 ±0.8 in adult (-3.9 mM) and from 8.7 ±1.9to4.7 ± 0.9 in senescent (4-.0 mM) papillary muscles, while developed tension (DT) increased by 80.2% in adult and by 135.6% in senescent papillary muscles (p <.01 vs adult). During low [Ca2+]0 and high [Na+]0, a'N> and DT modifications were similar both in adult and senescent papillary muscles. During high [Ca2+ ], a'Na decreased to a similar extent in both adult and senescent papillary muscles, while DT increased by 37.8% in adult and by 67.8% in senescent (p <.05 vs adult). Simultaneousreductionof[Na+]0and[Ca2+]0decreasedaiN,from8.1 ±1.2to6.8 ±1.1 mM in adult (-1.3 mM), andfrom8.4 ±1.0to7.2 ±1.0. mM in senescent (-1.2 mM) papillary muscles while DT decreased by 22.1% in adult and by only 12.0% in senescent (p <.01 vs adult) papillary muscles. Simultaneous increase of [Na+]0 and [Ca2+]0 similarly increased a'N, in both adult senescent papillary muscles, but decreased DT by 28.5% in adult and by 11,7% in senescent (p <.01 vs adult). After [Na+]0 modifications, the equilibration time for the ratio of external and internal sodium ion activities was slowed in senescent papillary muscles (i.e., in low |Na+]0 solution the equilibration time was 4.6 ±0.9 min in adult and 6.3 ±1.2 min in senescent papillary muscles, p <.001). Conclusions. Similar changes of a'Na during transmembrane Na and Ca2+ gradients modifications associated to changes in contractile force seem to demonstrate that Na+-Ca2+ exchange is probably not modified by the aging process. However, the slow equilibration time for the ratio of Na+ activities might reflect an age-related reduction of the Na+-K+ pump activity.

Original languageEnglish
JournalJournals of Gerontology - Series A Biological Sciences and Medical Sciences
Volume51
Issue number5
Publication statusPublished - 1996

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Papillary Muscles
Sodium
Myocardium
Action Potentials
Ions
Calcium

ASJC Scopus subject areas

  • Ageing

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The role of aging on the control of contractile force by Na+-Ca2+ exchange in rat papillary muscle. / Abete, Pasquale; Ferrara, Nicola; Cioppa, Angelo.

In: Journals of Gerontology - Series A Biological Sciences and Medical Sciences, Vol. 51, No. 5, 1996.

Research output: Contribution to journalArticle

@article{68509642d4db4db48aa4cedbfb8d94f8,
title = "The role of aging on the control of contractile force by Na+-Ca2+ exchange in rat papillary muscle",
abstract = "Background. Sarcolemmal Na+-Ca2+ exchange system is believed to be fundamental to the control of cardiac contractility. However, the relation between Na+-Ca2+ exchange and the control of contractile force has not been studied in senescent myocardium. Methods. The role of Na+-Ca2+ exchange in the regulation of the cardiac muscle's contractile force was studied in adult and senescent papillary muscles by simultaneously measuring intracellular sodium activity (a'Nl), action potential, and contractile force while varying extracellular concentration of sodium and/or calcium. Results. Reductionof[Na+]0decreaseda'Nlfrom8.0 ±1.8to4.1 ±0.8 in adult (-3.9 mM) and from 8.7 ±1.9to4.7 ± 0.9 in senescent (4-.0 mM) papillary muscles, while developed tension (DT) increased by 80.2{\%} in adult and by 135.6{\%} in senescent papillary muscles (p <.01 vs adult). During low [Ca2+]0 and high [Na+]0, a'N> and DT modifications were similar both in adult and senescent papillary muscles. During high [Ca2+ ], a'Na decreased to a similar extent in both adult and senescent papillary muscles, while DT increased by 37.8{\%} in adult and by 67.8{\%} in senescent (p <.05 vs adult). Simultaneousreductionof[Na+]0and[Ca2+]0decreasedaiN,from8.1 ±1.2to6.8 ±1.1 mM in adult (-1.3 mM), andfrom8.4 ±1.0to7.2 ±1.0. mM in senescent (-1.2 mM) papillary muscles while DT decreased by 22.1{\%} in adult and by only 12.0{\%} in senescent (p <.01 vs adult) papillary muscles. Simultaneous increase of [Na+]0 and [Ca2+]0 similarly increased a'N, in both adult senescent papillary muscles, but decreased DT by 28.5{\%} in adult and by 11,7{\%} in senescent (p <.01 vs adult). After [Na+]0 modifications, the equilibration time for the ratio of external and internal sodium ion activities was slowed in senescent papillary muscles (i.e., in low |Na+]0 solution the equilibration time was 4.6 ±0.9 min in adult and 6.3 ±1.2 min in senescent papillary muscles, p <.001). Conclusions. Similar changes of a'Na during transmembrane Na and Ca2+ gradients modifications associated to changes in contractile force seem to demonstrate that Na+-Ca2+ exchange is probably not modified by the aging process. However, the slow equilibration time for the ratio of Na+ activities might reflect an age-related reduction of the Na+-K+ pump activity.",
author = "Pasquale Abete and Nicola Ferrara and Angelo Cioppa",
year = "1996",
language = "English",
volume = "51",
journal = "Journals of Gerontology - Series A Biological Sciences and Medical Sciences",
issn = "1079-5006",
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number = "5",

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T1 - The role of aging on the control of contractile force by Na+-Ca2+ exchange in rat papillary muscle

AU - Abete, Pasquale

AU - Ferrara, Nicola

AU - Cioppa, Angelo

PY - 1996

Y1 - 1996

N2 - Background. Sarcolemmal Na+-Ca2+ exchange system is believed to be fundamental to the control of cardiac contractility. However, the relation between Na+-Ca2+ exchange and the control of contractile force has not been studied in senescent myocardium. Methods. The role of Na+-Ca2+ exchange in the regulation of the cardiac muscle's contractile force was studied in adult and senescent papillary muscles by simultaneously measuring intracellular sodium activity (a'Nl), action potential, and contractile force while varying extracellular concentration of sodium and/or calcium. Results. Reductionof[Na+]0decreaseda'Nlfrom8.0 ±1.8to4.1 ±0.8 in adult (-3.9 mM) and from 8.7 ±1.9to4.7 ± 0.9 in senescent (4-.0 mM) papillary muscles, while developed tension (DT) increased by 80.2% in adult and by 135.6% in senescent papillary muscles (p <.01 vs adult). During low [Ca2+]0 and high [Na+]0, a'N> and DT modifications were similar both in adult and senescent papillary muscles. During high [Ca2+ ], a'Na decreased to a similar extent in both adult and senescent papillary muscles, while DT increased by 37.8% in adult and by 67.8% in senescent (p <.05 vs adult). Simultaneousreductionof[Na+]0and[Ca2+]0decreasedaiN,from8.1 ±1.2to6.8 ±1.1 mM in adult (-1.3 mM), andfrom8.4 ±1.0to7.2 ±1.0. mM in senescent (-1.2 mM) papillary muscles while DT decreased by 22.1% in adult and by only 12.0% in senescent (p <.01 vs adult) papillary muscles. Simultaneous increase of [Na+]0 and [Ca2+]0 similarly increased a'N, in both adult senescent papillary muscles, but decreased DT by 28.5% in adult and by 11,7% in senescent (p <.01 vs adult). After [Na+]0 modifications, the equilibration time for the ratio of external and internal sodium ion activities was slowed in senescent papillary muscles (i.e., in low |Na+]0 solution the equilibration time was 4.6 ±0.9 min in adult and 6.3 ±1.2 min in senescent papillary muscles, p <.001). Conclusions. Similar changes of a'Na during transmembrane Na and Ca2+ gradients modifications associated to changes in contractile force seem to demonstrate that Na+-Ca2+ exchange is probably not modified by the aging process. However, the slow equilibration time for the ratio of Na+ activities might reflect an age-related reduction of the Na+-K+ pump activity.

AB - Background. Sarcolemmal Na+-Ca2+ exchange system is believed to be fundamental to the control of cardiac contractility. However, the relation between Na+-Ca2+ exchange and the control of contractile force has not been studied in senescent myocardium. Methods. The role of Na+-Ca2+ exchange in the regulation of the cardiac muscle's contractile force was studied in adult and senescent papillary muscles by simultaneously measuring intracellular sodium activity (a'Nl), action potential, and contractile force while varying extracellular concentration of sodium and/or calcium. Results. Reductionof[Na+]0decreaseda'Nlfrom8.0 ±1.8to4.1 ±0.8 in adult (-3.9 mM) and from 8.7 ±1.9to4.7 ± 0.9 in senescent (4-.0 mM) papillary muscles, while developed tension (DT) increased by 80.2% in adult and by 135.6% in senescent papillary muscles (p <.01 vs adult). During low [Ca2+]0 and high [Na+]0, a'N> and DT modifications were similar both in adult and senescent papillary muscles. During high [Ca2+ ], a'Na decreased to a similar extent in both adult and senescent papillary muscles, while DT increased by 37.8% in adult and by 67.8% in senescent (p <.05 vs adult). Simultaneousreductionof[Na+]0and[Ca2+]0decreasedaiN,from8.1 ±1.2to6.8 ±1.1 mM in adult (-1.3 mM), andfrom8.4 ±1.0to7.2 ±1.0. mM in senescent (-1.2 mM) papillary muscles while DT decreased by 22.1% in adult and by only 12.0% in senescent (p <.01 vs adult) papillary muscles. Simultaneous increase of [Na+]0 and [Ca2+]0 similarly increased a'N, in both adult senescent papillary muscles, but decreased DT by 28.5% in adult and by 11,7% in senescent (p <.01 vs adult). After [Na+]0 modifications, the equilibration time for the ratio of external and internal sodium ion activities was slowed in senescent papillary muscles (i.e., in low |Na+]0 solution the equilibration time was 4.6 ±0.9 min in adult and 6.3 ±1.2 min in senescent papillary muscles, p <.001). Conclusions. Similar changes of a'Na during transmembrane Na and Ca2+ gradients modifications associated to changes in contractile force seem to demonstrate that Na+-Ca2+ exchange is probably not modified by the aging process. However, the slow equilibration time for the ratio of Na+ activities might reflect an age-related reduction of the Na+-K+ pump activity.

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