Excitation-contraction in rat myocardium: Alterations with adult aging

J. Y. Wei, H. A. Spurgeon, E. G. Lakatta

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120 Scopus citations


Simultaneous transmembrane action potential (TAP) and isometric contraction measurements were made in thin right ventricular papillary muscles isolated from senescent (S, 24-26 mo) and young adult (YA, 6-8 mo) rat hearts. At the peak of the length-tension curve in the steady state at 24 min-1 at 29°C in perfusate [Ca2+] ([Ca2+](e)) of 0.375 or 2.5 mM, contractile tension developed in response to excitation (DT) and the maximum rate of tension development (dT/dt) were not age-related; contraction duration (CD) was 17 and 27% greater in S than YA in the low and high [Ca2+](e), respectively (P < 0.001); resting membrane potential was not age related. TAP time above zero mV, integrated area above zero mV, and times to 75% (T75) and 90% (T90) repolarization were approximately twofold greater in S than in YA in both [Ca2+](e) (P < 0.001). Changes in steady-state T75 and T90 due to an increase in [Ca2+](e) from 0.375 to 2.5 mM were significantly correlated with those in CD, DT, and dT/dt in S but not in YA. We conclude that in the senescent myocardium a prolonged and greater extent of depolarization is related to the prolonged CD and may also be a determinant of the peak force developed in response to excitation under some conditions.

Original languageEnglish (US)
Pages (from-to)H784-H791
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Issue number6
StatePublished - Jan 1 1984
Externally publishedYes

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)


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