Exercise capacity of rats remains unaffected by a chronic pressure overload.
OBJECTIVE
The aim was to determine if the adaptive responses of the myocardium to a chronic pressure overload affected cardiovascular performance when evaluated under conditions of increased functional demand.


METHODS
Selected female rats were made hypertensive by abdominal aortic constriction. After eight weeks of aortic constriction, cardiovascular responses and work performance were measured during a maximal treadmill exercise bout.


RESULTS
Aortic constriction increased mean arterial pressure and the relative quantity of the slow ATPase myosin isoform, V3, relative to untreated controls (p < 0.05). Both groups had similar oxygen consumptions (VO2), heart rates (HR), and oxygen pulses (VO2/HR) at rest and throughout the exercise test. Both groups reached their VO2 max at the same exercise duration and exercise intensity (40.4 m.min-1). Soleus citrate synthase activity was not different between the groups.


CONCLUSIONS
These similarities in work capacity, VO2, oxygen pulse, and muscle oxidative capacity suggest (1) that cardiovascular and exercise capacity can both be maintained in spite of the presence of a chronic pressure overload; (2) that after two months of aortic constriction the heart appears to be in a compensated stage of adaptation; and (3) that the cardiac myosin isoenzyme profile may have little direct effect on cardiovascular functional capacity.
Morris
G S
GS
Department of Physiology and Biophysics, University of California, Irvine.
Fitzsimons
D P
DP
Baldwin
K M
KM
Barnard
R J
RJ
D000818:Animals; D002950:Citrate (si)-Synthase / Q000378:metabolism; D004195:Disease Models, Animal; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006321:Heart / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology; D006973:Hypertension / Q000378:metabolism / Q000503:physiopathology*; D009206:Myocardium / Q000378:metabolism; D009218:Myosins / Q000378:metabolism; D010101:Oxygen Consumption / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley
D002950:Citrate (si)-Synthase; D009218:Myosins