Endurance training alters outward K+ current characteristics in rat cardiocytes. Jew, Korinne N., M. Charlotte Olsson, Eric A. Mokelke, Bradley M. Palmer, and Russell L. Moore. Department of Kinesiology and Applied Physiology, The University of Colorado Cardiovascular Institute, University of Colorado, Boulder, Colorado 80309«hyphen»0354
APStracts 8:0011A, 2001.
The effect of endurance run training on outward K+ currents with rapidly inactivating (Ito) and sustained or slowly inactivating (Isus) characteristics was examined in left ventricular (LV) cardiocytes isolated from sedentary (Sed) and treadmill-trained (Tr) female Sprague-Dawley rats. Isolated LV cardiocytes were used in whole cell patch- clamp studies to characterize whole cell Ito and Isus. Peak Ito was greatest in cells isolated from the Tr group. When Ito was corrected for cell capacitance to yield a current density, most, but not all, of the Sed vs. Tr differences in Ito magnitude were eliminated. Regardless of how Ito was expressed (e.g., Ito or Ito density), the time required to achieve a peak value was markedly shortened in the cardiocytes isolated from the Tr group. Training elicited a reduction in Isus density. Action potential characteristics were determined in Sed and Tr cardiocytes in primary culture. Training did not affect resting membrane potential, whereas peak membrane potential was reduced and time to peak membrane potential was prolonged in the Tr group. In addition, time to 50% repolarization was significantly increased in cells from the Tr group. Collectively, these data indicate that Ito and Isus characteristics are altered by training in isolated LV cardiocytes. These alterations in Ito and Isus may be responsible, at least in part, for the training-induced alterations in action potential configuration in cardiocytes in primary culture. 

Received 5 October 2000; accepted in final form 30 October 2000
APS Manuscript Number A176-0.
Article publication pending J Appl Physiol
ISSN 1080-4757 Copyright 2001 The American Physiological Society.
Published in APStracts on 29 January 2001