Training-induced elevation in FABPPM is associated with increased palmitate use in contracting muscle

Department of Exercise Sciences, University of Southern California, Los Angeles, California 90089-0652 To evaluate the effects of endurance training in rats on fatty acid metabolism, we measured the uptake and oxidation of palmitate in isolated rat hindquarters as well as the content of fatty acid-binding proteins in the plasma membranes (FABP PM ) of red and white muscles from 16 trained (T) and 18 untrained (UT) rats. Hindquarters were perfused with 6 mM glucose, 1,800 µM palmitate, and [1- 14 C]palmitate at rest and during electrical stimulation (ES) for 25 min. FABP PM content was 43-226% higher in red than in white muscles and was increased by 55% in red muscles after training. A positive correlation was found to exist between succinate dehydrogenase activity and FABP PM content in muscle. Palmitate uptake increased by 64-73% from rest to ES in both T and UT and was 48-57% higher in T than UT both at rest (39.8 ± 3.5 vs. 26.9 ± 4.4 nmol · min 1 · g 1 , T and UT, respectively) and during ES (69.0 ± 6.1 vs. 43.9 ± 4.4 nmol · min 1 · g 1 , T and UT, respectively). While the rats were resting, palmitate oxidation was not affected by training; palmitate oxidation during ES was higher in T than UT rats (14.8 ± 1.3 vs. 9.3 ± 1.9 nmol · min 1 · g 1 , T and UT, respectively). In conclusion, endurance training increases 1 ) plasma free fatty acid (FFA) uptake in resting and contracting perfused muscle, 2 ) plasma FFA oxidation in contracting perfused muscle, and 3 ) FABP PM content in red muscles. These results suggest that an increased number of these putative plasma membrane fatty acid transporters may be available in the trained muscle and may be implicated in the regulation of plasma FFA metabolism in skeletal muscle. electrical stimulation; fatty acid metabolism; fatty acid transport; fatty acid uptake; hindquarter perfusion; skeletal muscle; endurance training; muscle triglycerides; fatty acid-binding proteins in plasma membranes