Abstract des Autors

The interaction between systems regulating acid-base balance (i.e., CO2, strong ions, weak acids) was studied in sic subjects for 10 min after 30 s of maximal isokientic cycling during control conditions (CON) and after 3 days of chronic acetazolamide (ChACZ) administration (500 mg/8 h po) to inhibit carbonic anhydrase (CA). Gas exchange was measured; arterial and venous forearm blood was sampled for acid-base variables. Muscle power output was similar in ChACZ and CON, but peak O2 intake was lower in ChACZ; peak CO2 output was also lower in ChACZ (2,207 +/- 220 ml/min) than in CON (3,238 +/- 87 ml/min). Arterial PCO2 was lower at rest, and its fall after exercise was delayed in ChACZ. In ChACZ there was a higher arterial <Na+> and lower arterial <lactate-> (<La->) accompanied by lower arterial <K+> and higher arterial <Cl-> during the first part of recovery, resulting in a higher arterial plasma strong ion difference. Venoarterial (v-a) differences across theforearm showed a similar uptake of Na+, K+, Cl-, andLa- in ChACZ and CON. Arterial <H+> was higher and <HCO3-> was lower in ChACZ. Chronic CA inhibition impaired the efflux of CO2 from inactive muscle and its excretion by the lungs and also influenced the equilibration of strong ions. In contrast to our earlier study of acute CA inhibition the lower plasma arterial <La-> in ChACZ was accompanied by a similar La- uptake to CON related, in part, to the greater plasma acidosis that accompanied the longer duration of CA inhibition. Verf.-Referat