An estimate of the calcium content of the sarcoplasmic reticulum in rat ventricular myocytes

A. Varró, N. Negretti, S. B. Hester, D. A. Eisner

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Abstract

The aim of this paper was to estimate the Ca content of the sarcoplasmic reticulum (s.r.) and to compare this with the amount of Ca which enters the cell via the calcium current in systole. The s.r. Ca content was measured electrophysiologically in voltage-clamped rat ventricular myocytes. Rapid application of caffeine produced a transient increase of [Ca2+]i which was accompanied by a transient inward Na-Ca exchange current. The integral of this current gives a measure of the Ca2+ pumped out of the cell by Na-Ca exchange. Ni2+ (5 mM) inhibited the current and decreased the rate of fall of [Ca2+]i to 32% of the control suggesting that Na-Ca exchange is responsible for 68% of Ca removal from the cytoplasm following the addition of caffeine. Correcting for the Na-Ca independent Ca removal suggests that the s.r. Ca content is equivalent to about 120 μmol per litre cell. Furthermore we estimate that, during systole, Ca entry into the cell via the sarcolemmal calcium current is equal to about 6 % of the Ca content of the s.r.

Original languageEnglish
Pages (from-to)158-160
Number of pages3
JournalPflugers Archiv European Journal of Physiology
Volume423
Issue number1-2
DOIs
Publication statusPublished - Apr 1993

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Sarcoplasmic Reticulum
Caffeine
Muscle Cells
Rats
Calcium
Systole
Electric potential
Cytoplasm

ASJC Scopus subject areas

  • Physiology

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An estimate of the calcium content of the sarcoplasmic reticulum in rat ventricular myocytes. / Varró, A.; Negretti, N.; Hester, S. B.; Eisner, D. A.

In: Pflugers Archiv European Journal of Physiology, Vol. 423, No. 1-2, 04.1993, p. 158-160.

Research output: Contribution to journalArticle

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AB - The aim of this paper was to estimate the Ca content of the sarcoplasmic reticulum (s.r.) and to compare this with the amount of Ca which enters the cell via the calcium current in systole. The s.r. Ca content was measured electrophysiologically in voltage-clamped rat ventricular myocytes. Rapid application of caffeine produced a transient increase of [Ca2+]i which was accompanied by a transient inward Na-Ca exchange current. The integral of this current gives a measure of the Ca2+ pumped out of the cell by Na-Ca exchange. Ni2+ (5 mM) inhibited the current and decreased the rate of fall of [Ca2+]i to 32% of the control suggesting that Na-Ca exchange is responsible for 68% of Ca removal from the cytoplasm following the addition of caffeine. Correcting for the Na-Ca independent Ca removal suggests that the s.r. Ca content is equivalent to about 120 μmol per litre cell. Furthermore we estimate that, during systole, Ca entry into the cell via the sarcolemmal calcium current is equal to about 6 % of the Ca content of the s.r.

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