Shortening and [Ca2+] dynamics of left ventricular myocytes isolated from exercise-trained rats

• Published in: Journal of applied physiology (1985) Vol. 85; no. 6; pp. 2159 - 2168
• Main Authors: Palmer, Bradley M, Thayer, Anne M, Snyder, Steven M, Moore, Russell L
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01-12-1998; American Physiological Society
• Subjects: Anatomy & physiology; Animals; Biological and medical sciences; Caffeine - pharmacology; Calcium; Calcium - metabolism; Cardiology; Electric Stimulation; Exercise; Female; Fundamental and applied biological sciences. Psychology; Fura-2; Heart; In Vitro Techniques; Models, Cardiovascular; Myocardial Contraction - drug effects; Myocardial Contraction - physiology; Myocardium - cytology; Myocardium - metabolism; Physical Conditioning, Animal; Physical Exertion - physiology; Rats; Rats, Sprague-Dawley; Rodents; Ventricular Function, Left - drug effects; Vertebrates: cardiovascular system; Heart; Viscoelasticity; Physical training; Calcium; Rat; Rodentia; Contractility; Mechanical properties; Left ventricle; Myocyte; Isolated organ; Biomechanics; Vertebrata; Mammalia; Endurance; Circulatory system; Heart cell
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/jappl.1998.85.6.2159

Department of Kinesiology and Applied Physiology University of
Colorado at Boulder, Boulder, Colorado 80309
The effects of run endurance training and fura 2 loading on the contractile function and
Ca 2+ regulation of rat left
ventricular myocytes were examined. In myocytes not loaded with fura 2, the maximal extent of myocyte shortening was reduced with training
under our pacing conditions [0.5 Hz at 2.0 and 0.75 mM external
Ca 2+ concentration
([Ca 2+ ] o )], although training had no
effect on the temporal characteristics. The "light" loading of
myocytes with fura 2 markedly suppressed (~50%) maximal shortening
in the sedentary and trained groups, although the temporal
characteristics of myocyte shortening were significantly prolonged in
the trained group. No discernible differences in the dynamic
characteristics of the intracellular
Ca 2+ concentration
([Ca 2+ ]) transient
were detected at 2.0 mM
[Ca 2+ ] o , although
peak [Ca 2+ ] and rate
of [Ca 2+ ] rise during
caffeine contracture were greater in the trained state at 0.75 mM
[Ca 2+ ] o . We conclude
that training induced a diminished myocyte contractile function under
the conditions studied here and a more effective coupling of inward
Ca 2+ current to sarcoplasmic
reticulum Ca 2+ release at low
[Ca 2+ ] o ,
and that fura 2 and its loading vehicle DMSO significantly alter the
intrinsic characteristics of myocyte contractile function and
Ca 2+ regulation.
fura 2; dimethyl sulfoxide; caffeine contracture; edge
detection