Determinants of maximal O2 uptake in rats selectively bred for endurance running capacity Article (Web of Science)

abstract

  • O2 transport during maximal exercise was studied in rats bred for extremes of exercise endurance, to determine whether maximal O2 uptake (V˙o 2 max) was different in high- (HCR) and low-capacity runners (LCR) and, if so, which were the phenotypes responsible for the difference. V˙o 2 maxwas determined in five HCR and six LCR female rats by use of a progressive treadmill exercise protocol at inspired Po 2 of ∼145 (normoxia) and ∼70 Torr (hypoxia). Normoxic V˙o 2 max (in ml · min−1 · kg−1) was 64.4 ± 0.4 and 57.6 ± 1.5 ( P < 0.05), whereas V˙o 2 max in hypoxia was 42.7 ± 0.8 and 35.3 ± 1.5 ( P < 0.05) in HCR and LCR, respectively. Lack of significant differences between HCR and LCR in alveolar ventilation, alveolar-to-arterial Po 2difference, or lung O2 diffusing capacity indicated that neither ventilation nor efficacy of gas exchange contributed to the difference in V˙o 2 max between groups. Maximal rate of blood O2 convection (cardiac output times arterial blood O2 content) was also similar in both groups. The major difference observed was in capillary-to-tissue O2transfer: both the O2 extraction ratio (0.81 ± 0.002 in HCR, 0.74 ± 0.009 in LCR, P < 0.001) and the tissue diffusion capacity (1.18 ± 0.09 in HCR and 0.92 ± 0.05 ml · min−1 · kg−1 · Torr−1in LCR, P < 0.01) were significantly higher in HCR. The data indicate that selective breeding for exercise endurance resulted in higher V˙o 2 max mostly associated with a higher transfer of O2 at the tissue level.

authors

  • Henderson, Kyle K.
  • Wagner, Harrieth
  • Favret, Fabrice
  • Britton, Steven L.
  • Koch, Lauren Gerard
  • Wagner, Peter D.
  • Gonzalez, Norberto C.

publication date

  • 2002

published in

number of pages

  • 9

start page

  • 1265

end page

  • 1274

volume

  • 93

issue

  • 4