Determinants of maximal O(2) uptake in rats selectively bred for endurance running capacity.
O(2) transport during maximal exercise was studied in rats bred for extremes of exercise endurance, to determine whether maximal O(2) uptake (VO(2 max)) was different in high- (HCR) and low-capacity runners (LCR) and, if so, which were the phenotypes responsible for the difference. VO(2 max) was determined in five HCR and six LCR female rats by use of a progressive treadmill exercise protocol at inspired PO(2) of approximately 145 (normoxia) and approximately 70 Torr (hypoxia). Normoxic VO(2 max) (in ml. min(-1). kg(-1)) was 64.4 +/- 0.4 and 57.6 +/- 1.5 (P < 0.05), whereas VO(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(2) difference, or lung O(2) diffusing capacity indicated that neither ventilation nor efficacy of gas exchange contributed to the difference in VO(2 max) between groups. Maximal rate of blood O(2) convection (cardiac output times arterial blood O(2) content) was also similar in both groups. The major difference observed was in capillary-to-tissue O(2) transfer: both the O(2) 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(-1) in LCR, P < 0.01) were significantly higher in HCR. The data indicate that selective breeding for exercise endurance resulted in higher VO(2 max) mostly associated with a higher transfer of O(2) at the tissue level.
Henderson
Kyle K
KK
Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, Kansas 66160-7401, USA.
Wagner
Harrieth
H
Favret
Fabrice
F
Britton
Steven L
SL
Koch
Lauren G
LG
Wagner
Peter D
PD
Gonzalez
Norberto C
NC
D000822:Animal Husbandry; D000818:Animals; D002196:Capillaries; D005260:Female; D008297:Male; D008931:Mitochondria, Muscle / Q000378:metabolism; D009043:Motor Activity / Q000502:physiology*; D018482:Muscle, Skeletal / Q000098:blood supply / Q000378:metabolism; D010100:Oxygen / Q000097:blood / Q000378:metabolism; D010101:Oxygen Consumption; D010807:Physical Endurance; D051381:Rats
D010100:Oxygen