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- Title
The cerebral metabolic ratio is 1.7 during maximal wholebody exercise in humans.
- Authors
Strømstad, Morten; Volianitis, Stefanos; Overgaard, Anders; Fabricius-Bjerre, Andreas; Bjarrum, Mille; Carlsson, Christelle; Petersen, Nicolas; Secher, Niels H.; Nielsen, Henning B.
- Abstract
The cerebral metabolic ratio (CMR; uptake of oxygen in relation to glucose + ½lactate) was evaluated when arterial lactate becomes high during maximal ergometer rowing in six males. Maximal exercise increased heart rate to 181 ± 2 beats*min-1 and arterial lactate reached 21.4 ± 0.8 mM while internal jugular venous lactate was 18.5 ± 0.8 mM; i.e. the difference between arterial and venous lactate increased from 0.1 ± 0.1 to 2.9 ± 0.9 mM. Arterial glucose increased and the arterial to jugular venous difference increased from 1.0 ± 0.2 to 1.7 ± 0.3 mM. Prior to exercise the CMR was 5.7 ± 0.6 and it decreased to a lowest level of 1.7 ± 0.1 at termination of exercise. Within two weeks, exercise was repeated with inspired 02 fractions of 0.17 and 0.30 and arterial hemoglobin O2 saturation was 95.5 ± 0.4, 88.9 ± 1.0 and 98.9 ± 0.2% for normoxia, hypoxia and hyperoxia, respectively. While the jugular venous O2 hemoglobin saturation was higher with hyperoxia as compared to hypoxia (64 ± 6 vs. 45 ± 2%), CMR reached similar levels as in normoxia. During intense cycling brain lactate metabolism was evaluated with infusion of stable [13C]-lactate isotopes in one subject and significant 13CO2 appeared in venous blood. During maximal ergometer rowing, a low CMR is not affected by a change in cerebral O2 supply and the brain metabolises lactate when activated.
- Subjects
EXERCISE physiology; BRAIN; OXYGEN; GLUCOSE; LACTATES; METABOLISM; CYCLING
- Publication
FASEB Journal, 2007, Vol 21, Issue 6, pA836
- ISSN
0892-6638
- Publication type
Article
- DOI
10.1096/fasebj.21.6.a836-d