. Author manuscript; available in PMC: 2010 Jan 1.

Published in final edited form as: J Cereb Blood Flow Metab. 2008 Sep 3;29(1):108–118. doi: 10.1038/jcbfm.2008.102

Table 1.

Standard deviation of the glutamate–glutamine cycling flux determined using Monte Carlo analysis of the two-compartment model shown in Figure 1A with astroglial dilution^a,^b

Constraints (μmol/g/min)	Mean V_cyc (μmol/g/min)	Relative s.d. V_cyc^c(%)	Noise level (μmol/g)
None	0.16	34	0.2
	0.27	37	0.1
^aV_TCA≤0.1	0.32	37	0.2
	0.32	28	0.1
^aV_TCA≤0.1, V_efflux = 0.2V_Gln	0.26	28	0.2
	0.26	19	0.1
V_dil(Gln)^d	0.31	34	0.2
	0.33	19	0.1
V_dil(Lac)^d, V_dil(Gln)^d	0.32	29	0.2
	0.32	17	0.1
^aV_TCA≤0.1, V_dil(Lac)^d, V_dil(Gln)^d	0.33	28	0.2
	0.33	16	0.1

V_cyc, cerebral rate of the glutamate–glutamine cycle; V_TCA, tricarboxylic acid cycle flux; V_efflux, rate of glutamine efflux; V_dil(Gln), astroglial dilution flux rate; V_dil(Lac), lactate dilution flux rate.

All simulations were carried out with a total infusion time of 160 mins and temporal resolution of 5mins (32 time points). Only the glutamate C4 andglutamine C4 turnover curves were used for extraction of the metabolic fluxes.

Mean χ² of all simulations lies in the range of 59.0–60.8 with a standard deviation in the range of 10.9–11.4.

With respect to the nominal V_cyc=0.32 μmol/g/min.

Constrained to the mean flux rates given in ‘Materials and methods’.