Table 4.

Effect of Met and GAA supplementation on measurements derived from Met flux

	0 Met			6 g/d Met
	GAA, g/d							P-value 1
Flux, mmol Met/hr	0	7.5	15	0	7.5	15	SEM	Met	G-L	G-Q	Met × G-L	Met × G-Q
n	6	6	6	6	5	5
1-13C-l-Met	8.02	10.08	9.94	13.71	11.95	11.10	1.18	<0.01	0.73	0.71	0.04	0.38
Methyl-2H3-l-Met	10.68	12.74	13.18	13.67	12.90	12.59	0.86	0.17	0.34	0.65	0.03	0.42
Metabolizable Met2	1.31	1.31	1.30	2.97	2.97	2.99	0.01	<0.001	0.75	0.69	0.21	0.53
Met deposition3	0.95	0.86	0.92	1.14	1.13	1.31	0.09	<0.01	0.34	0.21	0.19	0.88
Protein synthesis4	7.63	9.65	9.55	11.89	10.12	9.42	1.19	0.10	0.78	0.76	0.04	0.36
Protein degradation5	6.70	8.77	8.64	10.74	8.98	8.12	1.18	0.18	0.73	0.71	0.04	0.38
Hcys production6	2.95	3.12	3.59	1.85	2.87	2.63	0.99	0.49	0.28	0.90	0.69	0.75
Transsulfuration7	0.36	0.45	0.38	1.84	1.85	1.68	0.09	<0.01	0.35	0.19	0.23	0.88
Remethylation8	2.60	2.64	3.16	0.11	0.96	1.44	0.97	0.02	0.31	0.97	0.67	0.79

¹G-L, linear effect of GAA; G-Q, quadratic effect of GAA.

²Metabolizable Met = ((DM intake, kg/hr × 6.71 mmol metabolizable Met/kg DM intake [Campbell et al., 1997]) + supplemental Met.

³Met deposition = N retention, g/hr × 6.25 g protein/g N × 0.134 mmol Met/g protein (Ainslie et al., 1993).

⁴Protein synthesis = PD + Met deposition.

⁵Protein degradation = 1-¹³C-l-Met flux − metabolizable Met.

⁶Homocysteine production (use of Met in methylation reactions) = Methyl-²H₃-l-Met flux – PS.

⁷Transsulfuration = 1-¹³C-l-Met flux – PS.

⁸Remethylation = Methyl-²H₃-l-Met flux – 1-¹³C-l-Met flux.