Table 3.

Plasma phenylalanine concentrations and enrichments and muscle free and protein-bound phenylalanine enrichments during basal, postabsorptive conditions and during the hyperinsulinemic-hyperaminoacidemic clamp in young and old men

Time (min)	Concentration		Enrichment
	(μM)		Muscle protein bound TTR		Muscle free TTR		Plasma TTR
	Young	Old	Young	Old	Young	Old	Young	Old
Basal conditions
60	59 ± 8	64 ± 9	0.000033 ± 0.000007	0.000101 ± 0.000026	0.0488 ± 0.0037	0.0545 ± 0.0044	0.0921 ± 0.0055	0.0929 ± 0.0066
90	48 ± 6	67 ± 8	---	---	---	---	0.1030 ± 0.0077	0.0993 ± 0.0090
120	58 ± 9	63 ± 8	---	---	---	---	0.1032 ± 0.0056	0.1119 ± 0.0093
150	53 ± 9	61 ± 9	---	---	---	---	0.1118 ± 0.0119	0.1130 ± 0.0067
180	56 ± 10	63 ± 9	---	---	---	---	0.1088 ± 0.0034	0.1129 ± 0.0056
210	60 ± 7	66 ± 8	---	---	---	---	0.1093 ± 0.0031	0.1155 ± 0.0078
240	59 ± 8	64 ± 9	0.000099 ± 0.000009	0.000186 ± 0.000029	0.0589 ± 0.0027	0.0686 ± 0.0048	0.1065 ± 0.0032	0.1194 ± 0.0079
Δ (240 – 60 min)			0.000067 ± 0.000009	0.000085 ± 0.000013
Mean	56 ± 7	64 ± 8			0.0539 ± 0.0028	0.0615 ± 0.0041	0.1050 ± 0.0051	0.1093 ± 0.0071
Hyperinsulinemic-hyperaminoacidemic clamp
270	93 ± 14	97 ± 10	---	---	---	---	0.0969 ± 0.0031	0.1108 ± 0.0045
300	88 ± 12	97 ± 10	---	---	---	---	0.0958 ± 0.0034	0.1028 ± 0.0042
330	116 ± 18	107 ± 14	---	---	---	---	0.0942 ± 0.0022	0.1005 ± 0.0050
360	85 ± 10	121 ± 14	---	---	---	---	0.0950 ± 0.0025	0.1000 ± 0.0044
390	98 ± 12	128 ± 16	---	---	---	---	0.0937 ± 0.0013	0.1021 ± 0.0055
420	108 ± 14	116 ± 17	0.000235 ± 0.000023	0.000310 ± 0.000038	0.0719 ± 0.0030	0.0806 ± 0.0033	0.0960 ± 0.0019	0.0952 ± 0.0055
Δ (420 – 240 min)			0.000136 ± 0.000015	0.000124 ± 0.000020
Mean	98 ± 12	111 ± 12			0.0654 ± 0.0027	0.0746 ± 0.0038	0.0953 ± 0.0021	0.1019 ± 0.0043

Values are means ± SEM.