. Author manuscript; available in PMC: 2009 Dec 1.

Published in final edited form as: Ann N Y Acad Sci. 2008 Dec;1147:139–170. doi: 10.1196/annals.1427.011

Table 1.

Oxygen utilization does not match glucose or glucose plus lactate consumption during brain activation.

A. Brain of normal conscious subjects
Human			Rest	Activation^c	Reference

	Whole brain (A-V difference assays)
		CMR_O2/CMR_glc	6.1	5.4	60
		CMR_O2/CMR_glc	6.04^a	5.35^a (ns)	61
		CMR_O2/CMR_{(glc+1/2 lactate)}	5.92^a	4.70^a	61
		CMR_O2/CMR_glc	5.95^a	6.02^a (ns)	62
		CMR_O2/CMR_{(glc+1/2 lactate)}	5.84^a	4.42^a	62
		CMR_O2/CMR_glc	5.8^a	5.89^a (ns)	63
		CMR_O2/CMR_{(glc+1/2 lactate)}	6.11^a	4.35^a	63
	Primary visual cortex (PET assays)
		CMR_O2/CMR_glc	4.1^b	2.8	64
		CMR_O2/CMR_glc	6.2	4.8	65
Rat
	Cerebral cortex (A-V difference assays)
		CMR_O2/CMR_glc	5.94	5.10	66
		CMR_O2/CMR_glc	6.1	5.0	38
		CMR_O2/CMR_glc	6.1	4.0	67
B. Eye of anesthetized subjects
			Light	Dark (Activated)

Cat (A-V differences: CMR_O2/CMR_glc)
	Outer retina^d (choroidal vein)		1.35	0.84	68
Pig (A-V differences: CMR_O2/CMR_glc)
	Inner retina (retinal vascular bed)		5.14	4.14	69
	Outer retina^d		0.55	0.51	70
		Whole uvea (vortex vein )	0.87	0.78	70

Substrate utilization ratios previously summarized in ref. 33 were calculated from (i) arteriovenous differences (A-V) for oxygen and glucose or glucose plus lactate (note: dividing the lactate uptake by two converts it to glucose equivalents) measured in paired samples of blood from the jugular bulb (human whole brain), sagittal sinus (rat cerebral cortex), or identified veins of the eye or (ii) metabolic rates for oxygen and glucose determined by positron emission tomography (PET).

Ratios during rest or physical exercise, which markedly increases blood lactate levels and lactate uptake into brain from blood (reviewed by Ide & Secher⁷¹ and Dalsgaard³⁷).

Note that the baseline ‘resting’ ratios are, for unexplained reasons, much lower than the expected value of about 6 observed in most studies (6 moles of oxygen are required for complete oxidation of 1 mole of glucose), but a further decrease was observed during activation.

All values during activation or exercise were statistically significantly different from rest, except those indicated by ‘ns’, denoting ‘not significant’.

Outer retina includes retinal pigment epithelium and photoreceptors; the whole uvea also includes the anterior uvea and contribution of aqueous humor⁷⁰.