Time course evaluation of protein synthesis and glucose uptake after acute resistance exercise in rats

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Abstract
The temporal pattern for changes in rates of protein synthesis and glucose uptake after resistance exercise, especially relative to each other, is not known. Male Sprague-Dawley rats performed acute resistance exercise (n = 7) or remained sedentary (n = 7 per group), and the following were assessed in vivo 1, 3, 6, 12 and 24 h later: rates of protein synthesis, rates of glucose uptake, phosphatidylinositol 3-kinase (PI3-kinase) activity, and p70S6k activity. Rates of protein synthesis in mixed gastrocnemius muscle did not increase until 12 h after exercise (e.g., at 12 h, sedentary = 138 ± 4 vs. exercised = 178 ± 6 nmol phenylalanine incorporated ⋅ g muscle−1 ⋅ h−1, mean ± SE, P < 0.05), whereas at 6 h after exercise rates of glucose uptake were significantly elevated (sedentary = 0.18 ± 0.020 vs. exercised = 0.38 ± 0.024 μmol glucose 6-phosphate incorporated ⋅ kg muscle−1 ⋅ min−1,P < 0.05). At 24 h after exercise, rates of protein synthesis were still elevated, whereas glucose uptake had returned to basal levels. Arterial insulin concentrations were not different between groups at any time. Non-insulin-stimulated activities of PI3-kinase and p70S6k were higher at 6, 12, and 24 h after exercise (P < 0.05), and, generally, these occurred when rates of protein synthesis (12 and 24 h) and glucose uptake were elevated (6 and 12 but not 24 h) by exercise. These data suggest that regulators of protein synthesis and glucose uptake may respond to the same contraction-generated signals with different kinetics or that they respond to different intra- or extracellular signals that are generated by exercise.