Table 1.

Fetal skeletal muscle protein metabolic rates

Flux rates (μmol min−1 100 g−1)	Equation	CON (n = 8)	IUGR (n = 11)	P
Net Leu uptake rate	(CLeuA – CLeuV) × PF	0.28 ± 0.02	0.20 ± 0.02	<0.05
Net KIC uptake rate	(CKICA – CKICV) × PF	0.03 ± 0.02	−0.00 ± 0.01	0.06
Inward Leu transport rate (FM,A)	{[(ELeuM – ELeuV/ELeuA – ELeuM) × CLeuV] + CLeuA} × PF	0.95 ± 0.91	0.64 ± 0.07	<0.05
Outward Leu transport rate (FV,M)	{[(ELeuM – ELeuV/ELeuA – ELeuM) × CLeuV] + CLeuV} × PF	0.68 ± 0.08	0.50 ± 0.05	0.06
Intracellular Leu utilization rate	[(CLeuA × ELeuA) – (CLeuV × ELeuV)] × PF/ELeuM	0.57 ± 0.05	0.39 ± 0.06	<0.05
Protein breakdown rate	Intracellular Leu utilization rate – Net Leu uptake rate	0.28 ± 0.04	0.19 ± 0.04	0.1
Leu oxidation rate	[(CCO2V × ECO2V) – (CCO2A × ECO2A)] × BF/EKICA	0.15 ± 0.02	0.12 ± 0.02	0.3
Leu oxidation fraction	Leu oxidation rate/Intracellular Leu utilization rate	0.27 ± 0.03	0.35 ± 0.04	0.2
Protein synthesis rate	Intracellular utilization – Leu oxidation rate	0.42 ± 0.04	0.27 ± 0.05	<0.05
Protein accretion rate	Net Leu uptake rate + Net KIC uptake rate – Leu oxidation rate	0.17 ± 0.03	0.08 ± 0.02	<0.05

Values are the mean ± SEM. P values are from Student's t tests or the Mann–Whitney test. All rates are μmol min⁻¹ 100 g hindlimb weight⁻¹.

PF, external iliac arterial plasma flow; BF, external iliac blood flow. F_X,Y refers to the rate of flow of leucine from pool y to pool x, where A, M, and V represent artery, muscle and vein, respectively. C_A and C_V are plasma concentrations and E_A and E_V are enrichments in the external iliac artery and femoral vein, respectively.