Lactate transport activity in rat skeletal muscle sarcolemmal vesicles after acute exhaustive exercise

The effect of a single bout of exhaustive exercise on muscle lactate transport capacity was studied in rat skeletal muscle sarcolemmal (SL) vesicles. Rats were assigned to a control (C) group (n = 14) or an acutely exercised (E) group (n = 20). Exercise consisted of treadmill running (25 m/min, 10% grade) to exhaustion. SL vesicles purified from C and E rats were sealed because of sensitivity to osmotic forces. The time course of 1 mM lactate uptake in zero-trans conditions showed that the equilibrium level in the E group was significantly lower than in the C group (P < 0.05). The initial rate of 1 mM lactate uptake decreased significantly from 2.44 ± 0.22 to 1.03 ± 0.08 nmol ⋅ min−1 ⋅ mg protein−1(P < 0.05) after exercise, whereas that of 50 mM lactate uptake did not differ significantly between the two groups. For 100 mM external lactate concentration ([lactate]), exhaustive exercise increased initial rates of lactate uptake (219.6 ± 36.3 to 465.4 ± 80.2 nmol ⋅ min−1 ⋅ mg protein−1,P < 0.05). Although s...