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Research Article Free access | 10.1172/JCI105658

Influence of the Thyroid State on the Intrinsic Contractile Properties and Energy Stores of the Myocardium

Robert A. Buccino, James F. Spann Jr., Peter E. Pool, Edmund H. Sonnenblick, and Eugene Braunwald

Cardiology Branch, National Heart Institute, Bethesda, Maryland

*

Received for publication 29 March 1967 and in revised form 9 June 1967.

Address requests for reprints to Dr. Engene Braunwald, Cardiology Branch, National Heart Institute, Bethesda, Md. 20014.

Find articles by Buccino, R. in: PubMed | Google Scholar

Cardiology Branch, National Heart Institute, Bethesda, Maryland

*

Received for publication 29 March 1967 and in revised form 9 June 1967.

Address requests for reprints to Dr. Engene Braunwald, Cardiology Branch, National Heart Institute, Bethesda, Md. 20014.

Find articles by Spann, J. in: PubMed | Google Scholar

Cardiology Branch, National Heart Institute, Bethesda, Maryland

*

Received for publication 29 March 1967 and in revised form 9 June 1967.

Address requests for reprints to Dr. Engene Braunwald, Cardiology Branch, National Heart Institute, Bethesda, Md. 20014.

Find articles by Pool, P. in: PubMed | Google Scholar

Cardiology Branch, National Heart Institute, Bethesda, Maryland

*

Received for publication 29 March 1967 and in revised form 9 June 1967.

Address requests for reprints to Dr. Engene Braunwald, Cardiology Branch, National Heart Institute, Bethesda, Md. 20014.

Find articles by Sonnenblick, E. in: PubMed | Google Scholar

Cardiology Branch, National Heart Institute, Bethesda, Maryland

*

Received for publication 29 March 1967 and in revised form 9 June 1967.

Address requests for reprints to Dr. Engene Braunwald, Cardiology Branch, National Heart Institute, Bethesda, Md. 20014.

Find articles by Braunwald, E. in: PubMed | Google Scholar

Published October 1, 1967 - More info

Published in Volume 46, Issue 10 on October 1, 1967
J Clin Invest. 1967;46(10):1669–1682. https://doi.org/10.1172/JCI105658.
© 1967 The American Society for Clinical Investigation
Published October 1, 1967 - Version history
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Abstract

The intrinsic contractile properties of isolated cat papillary muscles and myocardial high energy phosphate stores were examined at three levels of thyroid activity and correlated with hemodynamic measurements in the intact animal. In addition, the relationship of thyroid state to endogenous norepinephrine stores and myocardial responsiveness to certain inotropic interventions were studied. In muscles from hyperthyroid cats, the velocity of shortening and the rate of tension development were markedly augmented, while duration of active state was decreased, compared to euthyroid muscles. These findings occurred in the presence and absence of intact norepinephrine stores and over a wide range of temperature and contraction frequency. The opposite changes occurred in muscles from hypothyroid cats. Isometric tension was slightly higher in muscles from hyperthyroid and lower in muscles from hypothyroid cats. The inotropic response to both norepinephrine and strophanthidin varied inversely with the level of thyroid state and allowed all three groups of muscles to reach a common ceiling of isometric tension regardless of thyroid state. Creatine phosphate and adenosine triphosphate stores were intact at all three levels of thyroid state. Thus, the level of thyroid activity profoundly affects the intrinsic contractile state of cardiac muscle, independent of both norepinephrine stores and alterations in high energy phosphate stores, and, in addition, modifies the responsiveness of cardiac muscle to inotropic agents.

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