title: Determinants of maximal oxygen uptake in rats acclimated to simulated altitude.
abstract: The effect of acclimation to hypoxia on maximal O2 uptake (VO2max), maximal cardiac output (Qmax), and arteriovenous O2 concentration difference (a-vCO2) was studied in male Sprague-Dawley rats acclimated for 3 wk to a barometric pressure of approximately 380 Torr (A rats). Nonacclimated control animals were pair-fed littermates maintained at an ambient barometric pressure of approximately 740 Torr (NA rats). Both A and NA rats exercised maximally on a treadmill with inspired PO2 maintained at either approximately 72 or 145 Torr. Arterial blood O2 concentration was significantly higher in A than in NA rats (16.0 +/- 0.6 vs. 12.4 +/- 0.3 ml/dl in hypoxia and 28.4 +/- 1.5 vs. 20.1 +/- 0.9 ml/dl in normoxia, respectively; both P < 0.05). During hypoxic exercise VO2max was slightly but significantly higher in A than in NA subjects (55.3 +/- 1.3 vs. 48.8 +/- 1.1 ml STPD.min-1 x kg-1; P < 0.05). In hypoxia a-vCO2 was 16.6 +/- 0.6 and 12.4 +/- 0.4 ml/dl and Qmax was 401 +/- 17 and 489 +/- 9 ml.min-1 x kg-1 in A and NA subjects, respectively (both P < 0.05). A rats showed both lower maximal heart rate and lower maximal stroke volume during hypoxic exercise. In normoxia there was no significant difference in VO2max between A and NA rats (71.8 +/- 2.7 vs. 73.9 +/- 3.1 ml.min-1 x kg-1). As with hypoxia, in normoxia a-vCO2 was significantly higher and Qmax was significantly lower in A than in NA animals.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Physiology, University of Kansas Medical Center, Kansas City 66160-7401.
authors.forename: N C
authors.initials: NC
authors.lastname: Gonzalez
authors.forename: R L
authors.initials: RL
authors.lastname: Clancy
authors.forename: P D
authors.initials: PD
authors.lastname: Wagner
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000136:Acid-Base Equilibrium; D000531:Altitude; D000818:Animals; D001273:Atmosphere Exposure Chambers; D002118:Calcium / Q000097:blood; D002302:Cardiac Output / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D008297:Male; D008954:Models, Biological; D010101:Oxygen Consumption / Q000502:physiology*; D011650:Pulmonary Alveoli / Q000378:metabolism; D011653:Pulmonary Diffusing Capacity / Q000502:physiology; D011659:Pulmonary Gas Exchange / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D002118:Calcium