Effect of acetazolamide on gas exchange and acid-base control after maximal exercise.
To investigate the interactions between the systems that contribute to acid-base homeostasis after severe exercise, we studied the effects of carbonic anhydrase inhibition on exchange of strong ions and CO2 in six subjects after 30 s of maximal isokinetic cycling exercise. Each subject exercised on two randomly assigned occasions, a control (CON) condition and 30 min after intravenous injection of 1,000 mg acetazolamide (ACZ) to inhibit blood carbonic anhydrase activity. Leg muscle power output was similar in the two conditions; peak O2 uptake (VO2) after exercise was lower in ACZ (2,119 +/- 274 ml/min) than in CON (2,687 +/- 113, P less than 0.05); peak CO2 production (VCO2) was also lower (2,197 +/- 241 in ACZ vs. 3,237 +/- 87 in CON, P less than 0.05) and was accompanied by an increase in the recovery half-time from 1.7 min in CON to 2.3 min in ACZ. Whereas end-tidal PCO2 was lower in ACZ than in CON, arterial PCO2 (PaCO2) was higher, and a large negative end-tidal-to-arterial difference (less than or equal to 20 Torr) was present in ACZ on recovery. In ACZ, postexercise increases in arterial plasma [Na+] and [K+] were greater but [La-] was lower. Arteriovenous differences across the forearm showed a greater uptake of La- and Cl- in CON than in ACZ. Carbonic anhydrase inhibition with ACZ, in addition to impairing equilibration of the CO2 system to the acid-base challenge of exercise, was accompanied by changes in equilibration of strong inorganic ions. A lowered plasma [La-] was not accompanied by greater uptake of La- by inactive muscle.
Kowalchuk
J M
JM
Department of Medicine, McMaster University Health Sciences Centre, Hamilton, Ontario, Canada.
Heigenhauser
G J
GJ
Sutton
J R
JR
Jones
N L
NL
D000086:Acetazolamide / Q000494:pharmacology*; D000136:Acid-Base Equilibrium / Q000187:drug effects* / Q000502:physiology; D000328:Adult; D001639:Bicarbonates / Q000097:blood; D002245:Carbon Dioxide; D015444:Exercise / Q000502:physiology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007811:Lanthanum / Q000097:blood; D008297:Male; D010953:Plasma Volume / Q000502:physiology; D011188:Potassium / Q000097:blood; D011659:Pulmonary Gas Exchange / Q000187:drug effects* / Q000502:physiology; D012119:Respiration / Q000187:drug effects / Q000502:physiology; D012964:Sodium / Q000097:blood
D001639:Bicarbonates; D002245:Carbon Dioxide; D007811:Lanthanum; D012964:Sodium; D000086:Acetazolamide; D011188:Potassium