The effects of endurance training (running 40 m/min, 10% grade for 60 min, 5 days/wk for 8 wk) on skeletal muscle lactate removal was studied in rats by utilizing the isolated hindlimb perfusion technique. Hindlimbs were perfused (single-pass) with Krebs-Henseleit bicarbonate buffer, fresh bovine erythrocytes (hematocrit ∼30%), 10 mM lactate, and [U-14C]lactate (30,000 dpm/ml). Arterial and venous blood samples were collected every 10 min for the duration of the experiment to assess lactate uptake. During perfusions, no significant differences in skeletal muscle lactate uptake were observed between trained (7.31 ± 0.20 μmol/min) and control hindlimbs (6.98 ± 0.43 μmol/min). In support, no significant differences were observed for [14C]lactate uptake in trained (22,776 ± 370 dpm/min) compared with control hindlimbs (21,924 ± 1,373 dpm/min). Concomitant with these observations, no significant differences were observed between groups for oxygen consumption (4.93 ± 0.18 vs. 4.92 ± 0.13 μmol/min), net skeletal muscle glycogen synthesis (7.1 ± 0.4 vs. 6.5 ± 0.3 μmol · 40 min−1 · g−1), or14CO2 production (2,203 ± 185 vs. 2,098 ± 155 dpm/min), trained and control, respectively. These findings indicate that endurance training does not affect lactate uptake or alter the metabolic fate of lactate in quiescent skeletal muscle.
Lack of Skeletal Muscle Serotonin Impairs Physical Performance
