Peripheral chemoreceptor function after carbonic anhydrase inhibition during moderate-intensity exercise.
The effect of carbonic anhydrase inhibition with acetazolamide (Acz, 10 mg/kg) on the ventilatory response to an abrupt switch into hyperoxia (end-tidal PO2 = 450 Torr) and hypoxia (end-tidal PO2 = 50 Torr) was examined in five male subjects [30 +/- 3 (SE) yr]. Subjects exercised at a work rate chosen to elicit an O2 uptake equivalent to 80% of the ventilatory threshold. Ventilation (VE) was measured breath by breath. Arterial oxyhemoglobin saturation (%SaO2) was determined by ear oximetry. After the switch into hyperoxia, VE remained unchanged from the steady-state exercise prehyperoxic value (60.6 +/- 6.5 l/min) during Acz. During control studies (Con), VE decreased from the prehyperoxic value (52.4 +/- 5.5 l/min) by approximately 20% (VE nadir = 42.4 +/- 6.3 l/min) within 20 s after the switch into hyperoxia. VE increased during Acz and Con after the switch into hypoxia; the hypoxic ventilatory response was significantly lower after Acz compared with Con [Acz, change (Delta) in VE/DeltaSaO2 = 1.54 +/- 0.10 l. min-1. SaO2-1; Con, DeltaVE/DeltaSaO2 = 2.22 +/- 0.28 l. min-1. SaO2-1]. The peripheral chemoreceptor contribution to the ventilatory drive after acute Acz-induced carbonic anhydrase inhibition is not apparent in the steady state of moderate-intensity exercise. However, Acz administration did not completely attenuate the peripheral chemoreceptor response to hypoxia.
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; D000328:Adult; D001642:Bicycling / Q000502:physiology; D001784:Blood Gas Analysis; D002245:Carbon Dioxide / Q000097:blood; D002257:Carbonic Anhydrase Inhibitors / Q000494:pharmacology*; D002628:Chemoreceptor Cells / Q000187:drug effects*; D015444:Exercise / Q000502:physiology*; D006801:Humans; D018496:Hyperoxia / Q000503:physiopathology; D000860:Hypoxia / Q000503:physiopathology; D008297:Male; D010101:Oxygen Consumption / Q000187:drug effects / Q000502:physiology; D011659:Pulmonary Gas Exchange / Q000187:drug effects; D015656:Respiratory Mechanics / Q000187:drug effects / Q000502:physiology
D002257:Carbonic Anhydrase Inhibitors; D002245:Carbon Dioxide; D000086:Acetazolamide