Carbonic anhydrase inhibition delays plasma lactate appearance with no effect on ventilatory threshold.
The effect of carbonic anhydrase (CA) inhibition with acetazolamide (Acz, 10 mg/kg body wt iv) on exercise performance and the ventilatory (VET) and lactate (LaT) thresholds was studied in seven men during ramp exercise (25 W/min) to exhaustion. Breath-by-breath measurements of gas exchange were obtained. Arterialized venous blood was sampled from a dorsal hand vein and analyzed for plasma pH, PCO(2), and lactate concentration ([La(-)](pl)). VET [expressed as O(2) uptake (VO(2)), ml/min] was determined using the V-slope method. LaT (expressed as VO(2), ml/min) was determined from the work rate (WR) at which [La(-)](pl) increased 1.0 mM above rest levels. Peak WR was higher in control (Con) than in Acz sutdies [339 +/- 14 vs. 315 +/- 14 (SE) W]. Submaximal exercise VO(2) was similar in Acz and Con; the lower VO(2) at exhaustion in Acz than in Con (3.824 +/- 0. 150 vs. 4.283 +/- 0.148 l/min) was appropriate for the lower WR. CO(2) output (VCO(2)) was lower in Acz than in Con at exercise intensities >/=125 W and at exhaustion (4.375 +/- 0.158 vs. 5.235 +/- 0.148 l/min). [La(-)](pl) was lower in Acz than in Con during submaximal exercise >/=150 W and at exhaustion (7.5 +/- 1.1 vs. 11.5 +/- 1.1 mmol/l). VET was similar in Acz and Con (2.483 +/- 0.086 and 2.362 +/- 0.110 l/min, respectively), whereas the LaT occurred at a higher VO(2) in Acz than in Con (2.738 +/- 0.223 vs. 2.190 +/- 0.235 l/min). CA inhibition with Acz is associated with impaired elimination of CO(2) during the non-steady-state condition of ramp exercise. The similarity in VET in Con and Acz suggests that La(-) production is similar between conditions but La(-) appearance in plasma is reduced and/or La(-) uptake by other tissues is enhanced after the Acz treatment.
Scheuermann
B W
BW
Centre for Activity and Ageing, School of Kinesiology, The University of Western Ontario, London, Ontario, Canada N6A 3K7.
Kowalchuk
J M
JM
Paterson
D H
DH
Cunningham
D A
DA
D000086:Acetazolamide / Q000494:pharmacology*; D000136:Acid-Base Equilibrium; D000143:Acids / Q000097:blood; D000328:Adult; D000468:Alkalies / Q000097:blood; D015308:Anaerobic Threshold / Q000187:drug effects* / Q000502:physiology; D001784:Blood Gas Analysis; D002245:Carbon Dioxide / Q000097:blood; D002257:Carbonic Anhydrase Inhibitors / Q000494:pharmacology*; D002256:Carbonic Anhydrases / Q000187:drug effects*; D015444:Exercise / Q000502:physiology; D005080:Exercise Test; D006801:Humans; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000097:blood*; D008297:Male; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D005082:Physical Exertion / Q000502:physiology; D011659:Pulmonary Gas Exchange / Q000187:drug effects / Q000502:physiology; D012123:Pulmonary Ventilation / Q000187:drug effects / Q000502:physiology
D000143:Acids; D000468:Alkalies; D002257:Carbonic Anhydrase Inhibitors; D002245:Carbon Dioxide; D019344:Lactic Acid; D002256:Carbonic Anhydrases; D000086:Acetazolamide; D010100:Oxygen