In:
American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, American Physiological Society, Vol. 280, No. 4 ( 2001-04-01), p. R1240-R1248
Abstract:
We hypothesized that impaired O 2 transport plays a role in limiting exercise in patients with chronic renal failure (CRF). Six CRF patients (25 ± 6 yr) and six controls (24 ± 6 yr) were examined twice during incremental single-leg isolated quadriceps exercise. Leg O 2 delivery (Q˙o 2leg ) and leg O 2 uptake (V˙o 2leg ) were obtained when subjects breathed gas of three inspired O 2 fractions (Fi O 2 ) (0.13, 0.21, and 1.0). On a different day, myoglobin O 2 saturation and muscle bioenergetics were measured by proton and phosphorus magnetic resonance spectroscopy. CRF patients, but not controls, showed O 2 supply dependency of peak V˙o 2 (V˙o 2peak ) by a proportional relationship between peak V˙o 2leg at each inspired O 2 fraction (0.59 ± 0.20, 0.47 ± 0.10, 0.43 ± 0.10 l/min, respectively) and 1) work rate (933 ± 372, 733 ± 163, 667 ± 207 g), 2) Q˙o 2leg (0.80 ± 0.20, 0.64 ± 0.10, 0.59 ± 0.10 l/min), and 3) cell Po 2 (6.3 ± 5.4, 1.7 ± 1.3, 1.2 ± 0.7 mmHg). CRF patients breathing 100% O 2 and controls breathing 21% O 2 had similar peakQ˙o 2leg (0.80 ± 0.20 vs. 0.79 ± 0.10 l/min) and similar peak V˙o 2leg (0.59 ± 0.20 vs. 0.57 ± 0.10 l/min). However, mean capillary Po 2 (47.9 ± 4.0 vs. 38.2 ± 4.6 mmHg) and the capillary-to-myocite gradient (40.7 ± 6.2 vs. 34.4 ± 4.0 mmHg) were both higher in CRF patients than in controls ( P 〈 0.03 each). We conclude that low muscle O 2 conductance, but not limited mitochondrial oxidative capacity, plays a role in limiting exercise tolerance in these patients.
Type of Medium:
Online Resource
ISSN:
0363-6119
,
1522-1490
DOI:
10.1152/ajpregu.2001.280.4.R1240
Language:
English
Publisher:
American Physiological Society
Publication Date:
2001
detail.hit.zdb_id:
1477297-8
SSG:
12
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