PREEXERCISE BRANCHED-CHAIN AMINO-ACID ADMINISTRATION INCREASES ENDURANCE PERFORMANCE IN RATS

This study investigated the effects of pre-exercise branched-chain ami no acid (BCAA) administration on blood ammonia levels and on time to e xhaustion during treadmill exercise in rats. Adult female Wistar rats were trained on a motor driven treadmill. After a 24-h fast, rats were injected intraperitoneally (i.p.) with 1 mL of placebo or BCAA (30 mg ), 5 min before performing 30 min of submaximal exercise (N = 18) or r unning to exhaustion (N = 12). In both cases, rats were sacrificed imm ediately following exercise, and blood was collected for the measureme nt of glucose, nonesterified fatty acid (NEFA), lactic acid, BCAA, amm onia, and free-tryptophan (free-TRP) levels. Control values were obtai ned from sedentary rats that were subjected to identical treatments an d procedures (N = 30). Plasma BCAA levels increased threefold within 5 min after BCAA administration. Mean run time to exhaustion was signif icantly longer (P < 0.01) after BCAA administration (99 +/- 9 min) com pared with placebo (76 +/- 4 min). During exercise, blood ammonia leve ls were significantly higher (P < 0.01) in the BCAA treated compared w ith those in the placebo treated rats both in the 30-min exercise bout (113 +/- 25 mu mol.L-1 (BCAA) vs 89 +/- 16 mu mol.L-1) and following exercise to exhaustion (186 +/- 44 mu mol.L-1 (BCAA) vs 123 +/- 19 mu mol.L-1). These data demonstrate that BCAA administration in rats resu lts in enhanced endurance performance and an increase in blood ammonia during exercise.