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Peripheral chemoreceptor function after carbonic anhydrase inhibition during moderate-intensity exercise.
B W Scheuermann1, J M Kowalchuk, D H Paterson
1Centre for Activity and Ageing, School of Kinesiology, The University of Western Ontario, London, Ontario, Canada N6A 3K7.
Summary
Carbonic anhydrase inhibition with acetazolamide (Acz) blunts the ventilatory response to hypoxia during exercise. While Acz did not affect hyperoxic ventilation, it significantly reduced the hypoxic ventilatory response in male subjects.
Area of Science:
- Exercise Physiology
- Respiratory Physiology
- Pharmacology
Background:
- Carbonic anhydrase plays a role in chemoreception.
- Acetazolamide (Acz) is a carbonic anhydrase inhibitor.
- The effect of Acz on ventilatory control during exercise is not fully understood.
Purpose of the Study:
- To investigate the effect of carbonic anhydrase inhibition with acetazolamide (Acz) on the ventilatory response to hyperoxia and hypoxia during moderate-intensity exercise.
- To determine if Acz affects peripheral chemoreceptor sensitivity.
Main Methods:
- Five healthy male subjects exercised at 80% of their ventilatory threshold.
- Ventilation (VE) was measured breath-by-breath.
- Arterial oxyhemoglobin saturation (%SaO2) was monitored during abrupt switches to hyperoxia (450 Torr) and hypoxia (50 Torr) with and without Acz administration.
Main Results:
- During hyperoxia, VE remained unchanged with Acz, whereas it decreased by ~20% in control conditions.
- During hypoxia, the hypoxic ventilatory response (DeltaVE/DeltaSaO2) was significantly lower with Acz (1.54) compared to control (2.22).
- Acz did not completely abolish the peripheral chemoreceptor response to hypoxia.
Conclusions:
- Acute carbonic anhydrase inhibition with acetazolamide does not attenuate the steady-state ventilatory drive during moderate-intensity exercise.
- Acetazolamide significantly reduces the peripheral chemoreceptor-mediated ventilatory response to hypoxia during exercise.
- The peripheral chemoreceptor contribution to ventilatory control during exercise is modulated by carbonic anhydrase activity.