The Function Of Sarcoplasmic Reticulum In The Aged Rat Heart
type: CreativeWork
description: The purpose of this project was to study the effect of aging on the regulation of Ca{dollar}sp{lcub}2+{rcub}{dollar} by cardiac sarcoplasmic reticulum (SR) and its potential contribution to the age-related alterations in myocardial contractile performance in Fischer 344 rats.;In cardiac membranes enriched in SR (MSR) and its light (LSR) and heavy (HSR) subfractions fractionated by a sucrose density gradient, the rate of ATP-supported and oxalate-facilitated Ca{dollar}sp{lcub}2+{rcub}{dollar} uptake was significantly reduced (24-50%) in the aged (26-30 months old) compared with that of the adult rats (6-8 months old). With aging, the Ca{dollar}sp{lcub}2+{rcub}{dollar}-stimulated phosphoenzyme of the Ca{dollar}sp{lcub}2+{rcub}{dollar} pumps was reduced in MSR, LSR (25% and 33% respectively) but not in HSR; the Ca{dollar}sp{lcub}2+{rcub}{dollar}-ATPase activity was significantly reduced in LSR only (35%). The pump turnover rates were not significantly altered with aging in MSR, LSR and HSR. The coupling ratio was reduced by 26-46% in MSR but was not markedly altered in LSR and HSR. The density of the Ca{dollar}sp{lcub}2+{rcub}{dollar} release channels and the rate of Ca{dollar}sp{lcub}2+{rcub}{dollar}-induced Ca{dollar}sp{lcub}2+{rcub}{dollar} release from HSR were not altered with aging. Thus the age-related decline in the active Ca{dollar}sp{lcub}2+{rcub}{dollar} uptake by SR membranes is likely due to a reduction in the density of active Ca{dollar}sp{lcub}2+{rcub}{dollar} pumps and/or in the efficiency of Ca{dollar}sp{lcub}2+{rcub}{dollar} uptake by Ca{dollar}sp{lcub}2+{rcub}{dollar} pumps. The Ca{dollar}sp{lcub}2+{rcub}{dollar} release function of SR is not altered with aging. The reduced rate of SR Ca{dollar}sp{lcub}2+{rcub}{dollar} uptake may contribute to the prolonged myocardial relaxation in aging.;In the intact perfused heart, {dollar}beta{dollar}-adrenergic agonist isoproterenol-stimulated peak inotropic and lusitropic responses were significantly reduced wi…
abstract: The purpose of this project was to study the effect of aging on the regulation of Ca{dollar}sp{lcub}2+{rcub}{dollar} by cardiac sarcoplasmic reticulum (SR) and its potential contribution to the age-related alterations in myocardial contractile performance in Fischer 344 rats.;In cardiac membranes enriched in SR (MSR) and its light (LSR) and heavy (HSR) subfractions fractionated by a sucrose density gradient, the rate of ATP-supported and oxalate-facilitated Ca{dollar}sp{lcub}2+{rcub}{dollar} uptake was significantly reduced (24-50%) in the aged (26-30 months old) compared with that of the adult rats (6-8 months old). With aging, the Ca{dollar}sp{lcub}2+{rcub}{dollar}-stimulated phosphoenzyme of the Ca{dollar}sp{lcub}2+{rcub}{dollar} pumps was reduced in MSR, LSR (25% and 33% respectively) but not in HSR; the Ca{dollar}sp{lcub}2+{rcub}{dollar}-ATPase activity was significantly reduced in LSR only (35%). The pump turnover rates were not significantly altered with aging in MSR, LSR and HSR. The coupling ratio was reduced by 26-46% in MSR but was not markedly altered in LSR and HSR. The density of the Ca{dollar}sp{lcub}2+{rcub}{dollar} release channels and the rate of Ca{dollar}sp{lcub}2+{rcub}{dollar}-induced Ca{dollar}sp{lcub}2+{rcub}{dollar} release from HSR were not altered with aging. Thus the age-related decline in the active Ca{dollar}sp{lcub}2+{rcub}{dollar} uptake by SR membranes is likely due to a reduction in the density of active Ca{dollar}sp{lcub}2+{rcub}{dollar} pumps and/or in the efficiency of Ca{dollar}sp{lcub}2+{rcub}{dollar} uptake by Ca{dollar}sp{lcub}2+{rcub}{dollar} pumps. The Ca{dollar}sp{lcub}2+{rcub}{dollar} release function of SR is not altered with aging. The reduced rate of SR Ca{dollar}sp{lcub}2+{rcub}{dollar} uptake may contribute to the prolonged myocardial relaxation in aging.;In the intact perfused heart, {dollar}beta{dollar}-adrenergic agonist isoproterenol-stimulated peak inotropic and lusitropic responses were significantly reduced wi…
author: Jiang, Ming Tao
keywords: Biology, Animal Physiology
date published: 1995-01-01
date modified: 2026-07-27T21:56:03Z
provider: Western University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Western University

PropertyValue
property ID: Handle
value: https://hdl.handle.net/20.500.14721/17891