Human skeletal muscle carnitine palmitoyltransferase I activity determined in isolated intact mitochondria |
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Authors: | Berthon, Phanelie M. Howlett, Richard A. Heigenhauser, George J.F. Spriet, Lawrence L. |
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Abstract: | This study was designed to compare theactivity of skeletal muscle carnitine palmitoyltransferase I (CPT I) intrained and inactive men (n = 14) andwomen (n = 12). CPT Iactivity was measured in intact mitochondria, isolated from needlebiopsy vastus lateralis muscle samples (~60 mg). The variability ofCPT I activity determined on two biopsy samples from the same leg onthe same day was 4.4, whereas it was 7.0% on two biopsy samples fromthe same leg on different days. The method was sensitive to the CPT Iinhibitor malonyl-CoA (88% inhibition) and therefore specific for CPTI activity. The mean CPT I activity for all 26 subjects was 141.1 ± 10.6 µmol · min1 · kgwet muscle (wm)1 and wasnot different when all men vs. all women (140.5 ± 15.7 and 142.2 ± 14.5 µmol · min1 · kgwm1, respectively) were compared. However, CPT Iactivity was significantly higher in trained vs. inactive subjects forboth men (176.2 ± 21.1 vs. 104.1 ± 13.6 µmol · min1 · kgwm1) and women (167.6 ± 14.1 vs. 91.2 ± 9.5 µmol · min1 · kgwm1). CPT I activity was also significantly correlatedwith citrate synthase activity (all subjects,r = 0.76) and maximal oxygen consumption expressed in milliliters per kilogram per minute (all subjects, r = 0.69). Theresults of this study suggest that CPT I activity can be accurately andreliably measured in intact mitochondria isolated from human musclebiopsy samples. CPT I activity was not affected by gender, and higheractivities in aerobically trained subjects appeared to be the result ofincreased mitochondrial content in both men and women. |
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