Human skeletal muscle carnitine palmitoyltransferase I activity determined in isolated intact mitochondria.
This study was designed to compare the activity of skeletal muscle carnitine palmitoyltransferase I (CPT I) in trained and inactive men (n = 14) and women (n = 12). CPT I activity was measured in intact mitochondria, isolated from needle biopsy vastus lateralis muscle samples ( approximately 60 mg). The variability of CPT I activity determined on two biopsy samples from the same leg on the same day was 4.4, whereas it was 7.0% on two biopsy samples from the same leg on different days. The method was sensitive to the CPT I inhibitor malonyl-CoA (88% inhibition) and therefore specific for CPT I activity. The mean CPT I activity for all 26 subjects was 141.1 +/- 10.6 micromol . min-1 . kg wet muscle (wm)-1 and was not different when all men vs. all women (140.5 +/- 15.7 and 142.2 +/- 14.5 micromol . min-1 . kg wm-1, respectively) were compared. However, CPT I activity was significantly higher in trained vs. inactive subjects for both men (176.2 +/- 21.1 vs. 104.1 +/- 13.6 micromol . min-1 . kg wm-1) and women (167.6 +/- 14.1 vs. 91.2 +/- 9.5 micromol . min-1 . kg wm-1). CPT I activity was also significantly correlated with citrate synthase activity (all subjects, r = 0.76) and maximal oxygen consumption expressed in milliliters per kilogram per minute (all subjects, r = 0.69). The results of this study suggest that CPT I activity can be accurately and reliably measured in intact mitochondria isolated from human muscle biopsy samples. CPT I activity was not affected by gender, and higher activities in aerobically trained subjects appeared to be the result of increased mitochondrial content in both men and women.
Berthon
P M
PM
Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph, Ontario N1G 2W1.
Howlett
R A
RA
Heigenhauser
G J
GJ
Spriet
L L
LL
D000328:Adult; D002334:Carnitine O-Palmitoyltransferase / Q000378:metabolism*; D002950:Citrate (si)-Synthase / Q000378:metabolism; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008931:Mitochondria, Muscle / Q000201:enzymology*; D018482:Muscle, Skeletal / Q000201:enzymology*; D010101:Oxygen Consumption / Q000502:physiology; D010809:Physical Fitness / Q000502:physiology; D012727:Sex Characteristics
D002334:Carnitine O-Palmitoyltransferase; D002950:Citrate (si)-Synthase