Quinidine potentiates twitch tension and (at higher concentrations) causes contracture of skeletal muscle whereas the same drug reduces tension development of cardiac muscle. To gain insight into the possible differences in the excitation-contraction coupling mechanism of the two types of muscle the effect of quinidine on calcium accumulation by isolated sarcoplasmic reticulum from skeletal and cardiac muscle was investigated. In a medium containing ATP, Mg++, oxalate, and 45Ca, pharmacologically active concentrations of the drug inhibited calcium accumulation by both skeletal and cardiac sarcoplasmic reticulum. The inhibition of the rates of calcium, uptake by the skeletal muscle preparation ranged from 11% with 10-4M quinidine to 90% with 10-3 M quinidine. With the cardiac muscle preparation the inhibition ranged from 16% with 3 x 10-6 M quinidine to 100% with 10-3 M quinidine. With both preparations the inhibition of calcium transport was accompanied by an inhibition of the Ca++-activated ATPase activity of the sarcoplasmic reticulum. The effect of quinidine on the skeletal sarcoplasmic reticulum supports the hypothesis that this compound produces twitch potentiation and contracture by interfering with intracellular calcium, sequestration. Its effect on cardiac sarcoplasmic reticulum. has been interpreted in terms of the hypothesis that cardiac contractility is a function of the amount of calcium released from the sarcoplasmic reticulum which is in turn dependent upon the absolute calcium content of the reticulum. Hence, following inhibition of calcium transport there would be less calcium available for coupling.
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1 December 1968
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December 01 1968
The Effect of Quinidine on Calcium Accumulation by Isolated Sarcoplasmic Reticulum of Skeletal and Cardiac Muscle
Franklin Fuchs,
Franklin Fuchs
From the Department of Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213
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Edward W. Gertz,
Edward W. Gertz
From the Department of Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213
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F. Norman Briggs
F. Norman Briggs
From the Department of Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213
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Franklin Fuchs
From the Department of Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213
Edward W. Gertz
From the Department of Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213
F. Norman Briggs
From the Department of Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213
Received:
June 21 1968
Online ISSN: 1540-7748
Print ISSN: 0022-1295
Copyright © 1968 by The Rockefeller University Press
1968
J Gen Physiol (1968) 52 (6): 955–968.
Article history
Received:
June 21 1968
Citation
Franklin Fuchs, Edward W. Gertz, F. Norman Briggs; The Effect of Quinidine on Calcium Accumulation by Isolated Sarcoplasmic Reticulum of Skeletal and Cardiac Muscle . J Gen Physiol 1 December 1968; 52 (6): 955–968. doi: https://doi.org/10.1085/jgp.52.6.955
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