Table 1.

Glucose & Lactate Transport Capacities of Brain Cells

aCell	TRANSPORTER SPECIES	[Transporter]	[Transporter]	[Transporter]	bVmax uptake	bKm uptake	csubstrate/ligand	dkcat	epredicted Vmax in model
		pmol/mg membrane protein	carriers/μm2	pmol/mg total protein	nmol/106 cells/min	mM		per sec	mmol/sec
RBC	GLUT1	2000	2083	92	80.4	8	Glc/CB	1166
Endothelium	GLUT1	400	f1000	g18	0.21	8	CB	1166	7.8 × 10 −15
Astrocyte	GLUT1	7.3	f18	g0.34	4.8	8	CB	1166	j1.4 × 10 −16 k1.9 ×10−15
Neuron	GLUT3	9.5	f24	g0.44	h5.0 i34.6	2.8	3MG/CB	h868 i6512	2.3 × 10 −14
Extrapolated [MCT] values
RBC	MCT1	3.18	f8	g0.21	0.133	4	lactate	1166
Endothelium	MCT1	15.5	f39	g0.71	10	4	lactate	1166	3.0 × 10 −16
Astrocyte	MCT1/4	60.6	f151	g2.79	39	8	lactate	1166	j1.2 × 10 −15 k 1.5 × 10−14
Neuron	MCT2	11.7	f 29	g0.54	7.5	0.7	lactate	1166	4.9 × 10−15

^aCell in which transport is measured.

^bMeasured or computed maximum rate (V _max) or affinity (K_m) for transport.

^cThe substrate employed in transport (Glucose (Glc), 3-O-methylglucose (3MG) or lactate) or ligand GLUT quantitation experiments (Cytochalasin B (CB) binding).

^dComputed k _cat ([V_max/[GLUT]) for transport.

^ePredicted V _max for transport of glucose and lactate for use in the model.

^fAssumes 1 mg membrane protein is equivalent to a surface area of 2.4 × 10¹¹ μm².

^gAssumes that the ratio of membrane:total cellular protein is 0.0462 : 1.

^hMeasured at 25°C.

ⁱComputed for transport at 37°C assuming that GLUT3 and GLUT1 share the same temperature dependence.

^jDirection basal lamina to astrocyte.

^kDirection interstitium to astrocyte. Glucose transport parameters in endothelial cells, astrocytes and neurons were computed using estimated cell membrane GLUT contents and measured k _cat parameters. MCT concentrations are estimated assuming MCT k _cat = GLUT1 k _cat and using measured V _max values.