TY - JOUR

T1 - The cerebral metabolic ratio is not affected by oxygen availability during maximal exercise in humans

AU - Volianitis, S.

AU - Fabricius-Bjerre, A.

AU - Overgaard, A.

AU - Strømstad, M.

AU - Bjarrum, M.

AU - Carlson, C.

AU - Petersen, Nicolas Caesar

AU - Rasmussen, P.

AU - Secher, Niels

AU - Nielsen, H. B.

N1 - CURIS 2008 5200 017

PY - 2008

Y1 - 2008

N2 - Intense exercise decreases the cerebral metabolic ratio of O(2) to carbohydrates (glucose + (1/2) lactate) and the cerebral lactate uptake depends on its arterial concentration, but whether these variables are influenced by O(2) availability is not known. In six males, maximal ergometer rowing increased the arterial lactate to 21.4 +/- 0.8 mm (mean +/- s.e.m.) and arterial-jugular venous (a-v) difference from -0.03 +/- 0.01 mm at rest to 2.52 +/- 0.03 mm (P < 0.05). Arterial glucose was raised to 8.5 +/- 0.5 mm and its a-v difference increased from 1.03 +/- 0.01 to 1.86 +/- 0.02 mm (P < 0.05) in the immediate recovery. During exercise, the cerebral metabolic ratio decreased from 5.67 +/- 0.52 at rest to 1.70 +/- 0.23 (P < 0.05) and remained low in the early recovery. Arterial haemoglobin O(2) saturation was 92.5 +/- 0.2% during exercise with room air, and it reached 87.6 +/- 1.0% and 98.9 +/- 0.2% during exercise with an inspired O(2) fraction of 0.17 and 0.30, respectively. Whilst the increase in a-v lactate difference was attenuated by manipulation of cerebral O(2) availability, the cerebral metabolic ratio was not affected significantly. During maximal rowing, the cerebral metabolic ratio reaches the lowest value with no effect by a moderate change in the arterial O(2) content. These findings suggest that intense whole body exercise is associated with marked imbalance in the cerebral metabolic substrate preferences independent of oxygen availability.

AB - Intense exercise decreases the cerebral metabolic ratio of O(2) to carbohydrates (glucose + (1/2) lactate) and the cerebral lactate uptake depends on its arterial concentration, but whether these variables are influenced by O(2) availability is not known. In six males, maximal ergometer rowing increased the arterial lactate to 21.4 +/- 0.8 mm (mean +/- s.e.m.) and arterial-jugular venous (a-v) difference from -0.03 +/- 0.01 mm at rest to 2.52 +/- 0.03 mm (P < 0.05). Arterial glucose was raised to 8.5 +/- 0.5 mm and its a-v difference increased from 1.03 +/- 0.01 to 1.86 +/- 0.02 mm (P < 0.05) in the immediate recovery. During exercise, the cerebral metabolic ratio decreased from 5.67 +/- 0.52 at rest to 1.70 +/- 0.23 (P < 0.05) and remained low in the early recovery. Arterial haemoglobin O(2) saturation was 92.5 +/- 0.2% during exercise with room air, and it reached 87.6 +/- 1.0% and 98.9 +/- 0.2% during exercise with an inspired O(2) fraction of 0.17 and 0.30, respectively. Whilst the increase in a-v lactate difference was attenuated by manipulation of cerebral O(2) availability, the cerebral metabolic ratio was not affected significantly. During maximal rowing, the cerebral metabolic ratio reaches the lowest value with no effect by a moderate change in the arterial O(2) content. These findings suggest that intense whole body exercise is associated with marked imbalance in the cerebral metabolic substrate preferences independent of oxygen availability.

U2 - 10.1113/jphysiol.2007.142273

DO - 10.1113/jphysiol.2007.142273

M3 - Journal article

C2 - 17932151

VL - 586

SP - 107

EP - 112

JO - The Journal of Physiology

JF - The Journal of Physiology

SN - 0022-3751

IS - 1

ER -