Training-induced elevation in FABP(PM) is associated with increased palmitate use in contracting muscle

Training-induced elevation in FAB(PM) is associated with increased palmitat e use in contracting muscle. J. Appl. Physiol. 87(1): 285-293, 1999.-To eva luate the effects of endurance training in rats on fatty acid metabolism, w e measured the uptake and oxidation of palmitate in isolated rat hindquarte rs as well as the content of fatty acid-binding proteins in the plasma memb ranes (FABP(PM)) of red and white muscles from 16 trained (T) and 18 untrai ned (UT) rats. Hindquarters were perfused with 6 mM glucose, 1,800 mu M pal mitate, and [1-C-14]palmitate at rest and during electrical stimulation (ES ) for 25 min. FABP(PM) content was 43-226% higher in red than in white musc les and was increased by 55% in red muscles after training. A positive corr elation was found, to exist between succinate dehydrogenase activity and FA BP(PM) content in muscle. Palmitate uptake increased by 64-73% from rest to ES in both T and UT and uas 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 d uring ES (69.0 +/- 6.1. vs. 43.9 +/- 4.4 nmol.min(-1).g-(1), T and UT, resp ectively). While the rats were resting, palmitate oxidation was not affecte d 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). I n 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. The se results suggest that an increased number of these putative plasma membra ne fatty acid transporters may be available in the trained muscle and may b e implicated in the regulation of plasma FFA metabolism in skeletal muscle.