O2 uptake kinetics after acetazolamide administration during moderate- and heavy-intensity exercise Article (Web of Science)

abstract

  • Inhibition of carbonic anhydrase (CA) is associated with a lower plasma lactate concentration ([La−]pl) during fatiguing exercise. We hypothesized that a lower [La−]plmay be associated with faster O2uptake (V˙o 2) kinetics during constant-load exercise. Seven men performed cycle ergometer exercise during control (Con) and acute CA inhibition with acetazolamide (Acz, 10 mg/kg body wt iv). On 6 separate days, each subject performed 6-min step transitions in work rate from 0 to 100 W (below ventilatory threshold, <V˙eT) or to a V˙o 2 corresponding to ∼50% of the difference between the work rate atV˙eT and peakV˙o 2(>V˙eT). Gas exchange was measured breath by breath. Trials were interpolated at 1-s intervals and ensemble averaged to yield a single response. The mean response time (MRT, i.e., time to 63% of total exponential increase) for on- and off-transients was determined using a two- (<V˙eT) or a three-component exponential model (>V˙eT). Arterialized venous blood was sampled from a dorsal hand vein and analyzed for [La−]pl. MRT was similar during Con (31.2 ± 2.6 and 32.7 ± 1.2 s for on and off, respectively) and Acz (30.9 ± 3.0 and 31.4 ± 1.5 s for on and off, respectively) for work rates <V˙eT. At work rates >V˙eT, MRT was similar between Con (69.1 ± 6.1 and 50.4 ± 3.5 s for on and off, respectively) and Acz (69.7 ± 5.9 and 53.8 ± 3.8 s for on and off, respectively). On- and off-MRTs were slower for >V˙eT than for <V˙eT exercise. [La−]plincreased above 0-W cycling values during <V˙eT and >V˙eT exercise but was lower at the end of the transition during Acz (1.4 ± 0.2 and 7.1 ± 0.5 mmol/l for <V˙eT and >V˙eT, respectively) than during Con (2.0 ± 0.2 and 9.8 ± 0.9 mmol/l for <V˙eT and >V˙eT, respectively). CA inhibition does not affect O2 utilization at the onset of <V˙eT or >V˙eT exercise, suggesting that the contribution of oxidative phosphorylation to the energy demand is not affected by acute CA inhibition with Acz.

authors

publication date

  • 1998

webpage

published in

number of pages

  • 9

start page

  • 1384

end page

  • 1393

volume

  • 85

issue

  • 4