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 saturation kinetics were observed in the C group with a maximal transport velocity of 233 nmol. min(-1). mg protein(-1) and a Michealis-Menten constant of 24.5 mM, saturation properties were not seen after exhaustive exercise in the E group, because initial rates of lactate uptake increased linearly with external [lactate]. We conclude that a single bout of exhaustive exercise significantly modified SL lactate transport activity, resulting in a decrease in 1 mM lactate uptake and was associated with alterations in the saturable properties at [lactate] above 50 mM. These results suggest that changes in sarcolemmal lactate transport activity may alter lactate and proton exchanges after exhaustive exercise.
Dubouchaud
H
H
Laboratoire de Physiologie des Interactions, Service Central de Physiologie Clinique, Hôpital A de Villeneuve, 34295 Montpellier cedex 5, France.
Eydoux
N
N
Granier
P
P
Préfaut
C
C
Mercier
J
J
D000818:Animals; D001693:Biological Transport, Active / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D006003:Glycogen / Q000378:metabolism; D019344:Lactic Acid / Q000378:metabolism*; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000648:ultrastructure; D009994:Osmolar Concentration; D005082:Physical Exertion / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012420:Running / Q000502:physiology; D012508:Sarcolemma / Q000378:metabolism* / Q000648:ultrastructure
D019344:Lactic Acid; D006003:Glycogen