Determinants of maximal O₂ uptake in rats selectively bred for endurance running capacity

Abstract

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.

A meta-analysis ofin vivovertebrate cardiac performance: implications for cardiovascular support in the evolution of endothermy

“…The species used in this meta-analysis were: Chondricthyes -Triakis semifasciata (Lai et al, 1989(Lai et al, , 1990, Scyliorhinus stellaris (Piiper et al, 1977); Osteicthyes -Hemitripterus americanus (Axelsson et al, 1989), Anguilla australis (Davie and Forster, 1980), Gadus morhua (Axelsson, 1988;Axelsson and Nilsson, 1986;Gallaugher, 1994), Oncorhyncus mykiss (Kiceniuk and Jones, 1977), Pagothenia bernachii and P. borchgrevinki (Axelsson et al, 1992), Ophiodon elongatus (Farrell, 1982); AmphibiaRhinella marina (West and Smits, 1994;Hedrick et al, 1999); Aves -Columba livia (Grubb, 1982;Peters et al, 2005), Anas platyrhynchos (Grubb, 1982), Dromiceius novaehollandiae (Grubb et al, 1983); Mammalia -Homo sapiens (Brooks et al, 1996), Canis familiaris (Stray-Gunderson et al, 1986; Karas et al, 1987), Bos taurus (Karas et al, 1987), Equus caballus (Karas et al, 1987), Capra hircus (Karas et al, 1987) and Rattus norvegicus (Henderson et al, 2002). Data for these species are given in Table 1.…”

The effect of acute exercise session on thyroid hormone economy in rats

“…After the adaptation period, each rat was submitted to a maximum exercise test. We modified a ramp test for maximal treadmill running to measure the aerobic capacity of the animals (Henderson et al 2002), as described previously (Werneck-decastro et al 2006). Trial began at a starting velocity of 17 cm/s and a constant slope of 108.…”

Aerobic capacity in wild satin bowerbirds: repeatability and effects of age, sex and condition

“…pulmonary, cardiovascular, musculoskeletal, neural), it is likely to be a useful indicator of health and vigor. Hence, to the degree that it is heritable (Garland and Bennett, 1990;Dohm et al, 1996;Henderson et al, 2002), it may also be a signal of genetic quality. Aerobic performance variation has been extensively studied by mechanistic and ecological physiologists, but its role in mating systems, and especially in relation to female choice, has rarely been explored (Chappell et al, 1997).…”