EFFECTS OF EXERCISE ON LACTATE TRANSPORT INTO MOUSE SKELETAL-MUSCLES

Skeletal muscle lactate transport was investigated in vitro in isolate d fast-twitch (EDL) and slow-twitch soleus (Sol) skeletal muscles from control and exercised mice. Exercise (23 m/min, 8% grade) reduced mus cle glycogen by 37% in EDL (p < 0.05) and by 35% in Sol muscles (p < 0 .05). Lactate transport measurements (45 sec) were performed after 60 min of exercise in intact EDL and Sol muscles in vitro, at differing p H (6.5 and 7.4) and differing lactate concentrations (4 and 30 mM). La ctate transport was observed to be greater in Sol than in EDL (p < 0.0 5). In the exercised muscles there was a small but significant increas e in lactate transport (p < 0.05). Lactate transport was greater when exogenous lactate concentrations were gl eater (p < 0.05) and more rap id at the lower pH (p < 0.05). These studies demonstrated that lactate transport was increased with exercise.