Journal of Applied Physiology
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J Appl Physiol 95: 1799-1807, 2003. First published July 11, 2003; doi:10.1152/japplphysiol.00978.2002
8750-7587/03 $5.00
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Mild renal hypertension alters run training effects on the frequency response of rat cardiomyocyte mechanics

Bradley M. Palmer, Eric A. Mokelke, Anne M. Thayer, and Russell L. Moore

Department of Kinesiology and Applied Physiology, University of Colorado at Boulder, Boulder, Colorado 80309

Submitted 23 October 2002 ; accepted in final form 11 June 2003

We examined the effects of run training on the frequency dependence of cardiomyocyte mechanics and intracellular calcium concentration ([Ca2+]i) dynamics in rats with mild renal hypertension. Male Fischer 344 rats aged 2–3 mo underwent a sham operation or stenosis of the left renal artery, which increased systolic blood pressure 20–30 mmHg. Half of the rats in each group underwent treadmill run training for >16 wk. Isolated cardiomyocytes were paced at 1.0 and 0.2 Hz in 2 mM external Ca2+ concentration at 29°C. Under these conditions, negative frequency responses, i.e., decreased value with increased frequency, were recorded for peak shortening, shortening velocity, and the integral of the [Ca2+]i transient in both groups. Run training amplified the negative frequency response for the integral of the [Ca2+]i transient in both groups, but it amplified the negative frequency response for the shortening dynamics only in the normotensive sham-operated and not in the hypertensive rats. These results, as well as others for relaxation parameters, suggest that renal hypertension altered the effects of run training on the frequency response for cardiomyocyte contractile apparatus and/or passive mechanical properties, which respond to [Ca2+]i.

force-frequency relationship; relaxation-frequency relationship; calcium; treadmill


Address for reprint requests and other correspondence: R. L. Moore, Dept. of Integrative Physiology, Campus Box 354, University of Colorado, Boulder, CO 80309.






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