Figure 4. Postabsorptive and exercise-stimulated muscle protein synthesis. Muscle protein synthesis was measured from the rate of incorporation of isotopically labeled amino acid into muscle proteins. Protein synthesis was measured at baseline (postabsorptive) and 15-18 hours following a single bout of exercise for mixed muscle (MMP) (A, E), mitochondrial fraction (Mito) (B, F), sarcoplasmic fraction (Sarco) (C, G), and myofibrillar fraction (Myo) (D, H). Postabsorptive protein synthesis was similar in young and old in all fractions. Mixed muscle and myofibrillar protein synthesis increased with exercise in young but not old. Mitochondrial and sarcoplasmic protein synthesis increased with exercise in old but not young. n3-PUFA supplementation increased mitochondrial and myofibrillar protein synthesis after exercise. The change in FSR (Δ=post exercise-baseline) is shown in the right panel (E-H), illustrating responders and non-responders. * Significantly (p≤0.05) different from corresponding baseline value. Ψ Significantly different from corresponding pre-intervention value. # Significantly different from young. Data bars are mean ± SEM. Circles denote men and triangles denote women.