Chronic run training suppresses alpha-adrenergic response of rat cardiomyocytes and isovolumic left ventricle.
The effects of endurance run training on alpha-adrenergic responsiveness of rat left ventricle (LV) were examined in cardiomyocytes and isovolumic LV. Female Sprague-Dawley rats were sedentary (Sed) or trained (Tr) for >20 wk by treadmill running. Cardiomyocyte shortening and fura 2 fluorescence ratio were recorded before and during 5-min exposure to 5 microM phenylephrine (PE) while paced at 0.5 Hz in 2 mM extracellular Ca2+ concentration at 29 degrees C. Cardiomyocyte shortening and shortening velocity increased with PE, and these effects were more pronounced in the Sed group. The rate of cytosolic Ca2+ concentration removal was reduced by PE in the Sed cardiomyocytes, but was unaffected in the Tr. Isovolumic LV pressure was recorded immediately before and during 5-min perfusion with 5 microM PE during pacing at 280 beats/min and 37 degrees C, and positive inotropy due to PE was more pronounced in the Sed than in the Tr. These data demonstrated that the effects of alpha-adrenergic stimulation on myocardial positive inotropy and calcium regulation were reduced in this rat model of run training at both the cellular and whole organ levels.
Palmer
B M
BM
Department of Kinesiology and Applied Physiology, University of Colorado at Boulder, Boulder 80309, Colorado. palmerbm@spot.colorado.edu
Olsson
M C
MC
Lynch
J M
JM
Mace
L C
LC
Snyder
S M
SM
Valent
S
S
Moore
R L
RL
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D001835:Body Weight; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D005260:Female; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D006352:Heart Ventricles; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology*; D009206:Myocardium / Q000166:cytology; D009929:Organ Size; D010477:Perfusion; D010656:Phenylephrine / Q000494:pharmacology; D010805:Physical Conditioning, Animal / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D016277:Ventricular Function, Left / Q000502:physiology*
D000316:Adrenergic alpha-Agonists; D011942:Receptors, Adrenergic, alpha; D010656:Phenylephrine; D002118:Calcium