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Functional Genomics Laboratory, Medical College of Ohio, Toledo, Ohio 43614-5804
Rat genetic models of intrinsic (i.e.,
untrained) low-capacity runners (LCR) and high-capacity runners (HCR)
are being developed by artificial selective breeding for treadmill
running. At generation 3, these lines differed in running
capacity by 114%. We used generation 3 rats to test the
hypotheses that HCR, relative to LCR, have 1) greater
isolated cardiac performance and 2) more resistance to
myocardial ischemic insult. The LCR ran for 227 ± 7 m, and the HCR ran 994 ± 11 m at exhaustion (337%
difference, P < 0.001). Isolated heart performance was
assessed from cardiac output (CO) generated at constant preload (15 mmHg) and afterload (70 mmHg) using a Langendorff-Neely working heart
preparation. CO averaged 33.5 ± 2.0 ml · min
1 · g
1 in LCR
hearts and 49.9 ± 1.4 ml · min
1 · g
1 in HCR
hearts (49% difference, P < 0.001). Recovery of CO
after 25 min of global ischemia was not different between the
lines. These results suggest that 1) increased cardiac
performance accounts for part of the difference in running capacity
between the lines; and 2) unlike exercise training,
genetically determined intrinsic capacity for exercise does not
influence the recovery from 25 min of global low-flow cardiac ischemia.
treadmill; aerobic exercise
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