TABLE 2.

Plateau enrichment of stable isotope-labeled amino acids and their metabolic products and the corresponding flux values after infusion with [1,2-¹³C]glycine or [1-¹³C]glycine and [²H₃]leucine¹

	Protocol [1,2-13C]glycine		Protocol [1-13C]glycine
	Ep, mol % excess	Whole-body Q, μmol·h−1·kg−1	Ep, mol % excess	Whole-body Q, μmol·h−1·kg−1
Infused AA		Qinfused AA		Qinfused AA
[2H3]leucine	1.69 ± 0.15	109 ± 11	1.86 ± 0.11	99 ± 6
[13C2]glycine	5.54 ± 1.26	423 ± 79	5.36 ± 0.78	430 ± 62
CO2 generation		QGly→CO2		QGly→CO2
[13CO2]	0.046 ± 0.006	146 ± 37	0.033 ± 0.003*	96 ± 8‡

¹Values are mean ± SD, n = 6. Symbols indicate different from [1,2-¹³C]glycine protocol: *P = 0.0003; ^‡P = 0.026 (paired t test). AA, amino acids.