Muscle metabolism during heavy-intensity exercise after acute acetazolamide administration

Carbonic anhydrase (CA) inhibition is associated with a lower plasma lactate concentration ([La-](pl)), but the mechanism for this association is not known. The effect of CA inhibition on muscle high-energy phosphates [ATP and phosphocreatine (PCr)], lactate ([La-](m)), and glycogen was examined in seven men [28 +/- 3 (SE) yr] during cycling exercise under control (Con) and acute CA inhibition with acetazolamide (Acz; 10 mg/kg body wt iv). Subjects performed 6-min step transitions in work rate from 0 W to a work rate corresponding to similar to 50% of the difference between the O-2 uptake at the ventilatory threshold and peak O-2 uptake. Muscle biopsies were taken from the vastus lateralis at rest, at 30 min postinfusion, at end exercise (EE), and at 5 and 30 min postexercise. Arterialized venous blood was sampled from a dorsal hand vein and analyzed for [La-](pl). ATP was unchanged from rest values; no difference between Con and Act was observed. The fall in PCr from rest [72 +/- 3 and 73 +/- 3.6 (SE) mmol/kg dry wt for Con and Act, respectively] to EE (51 +/- 4 and 46 +/- 5 mmol/kg dry wt for Con and Act, respectively) was similar in Con and Act. At EE, glycogen (mmol glucosyl units/kg dry wt) decreased to similar values in Con and Act (307 +/- 16 and 300 +/- 19, respectively). At EE, no difference was observed in [La-], between conditions (46 +/- 6 and 43 +/- 5 mmol/kg dry wt for Con and Act, respectively). EE [La-](pl) was higher during Con than during Acz (11.4 +/- 1.0 vs. 8.2 +/- 0.6 mmol/l). The similar [La-](m) but lower [La-](pl) suggests that the uptake of La- by other tissues is enhanced after CA inhibition.