The effect of dopamine on pulmonary diffusing capacity and capillary blood volume responses to exercise in young healthy humans

Abstract

New Findings What is the Central question?Does dopamine, a pulmonary vascular vasodilator, contribute to the regulation of pulmonary diffusing capacity and capillary blood volume responses to exercise and exercise tolerance? What are the main findings and their importance?Dopamine appears not to be important for regulating pulmonary diffusing capacity or pulmonary capillary blood volume during exercise in healthy participants. Dopamine blockade trials demonstrated that endogenous dopamine is important for maintaining exercise tolerance; however, exogenous dopamine does not improve exercise tolerance. Abstract Pulmonary capillary blood volume (Vc) and diffusing membrane capacity (Dm) expansion are important contributors to the increased pulmonary diffusing capacity (DLCO) observed during upright exercise. Dopamine is a pulmonary vascular vasodilator, and recent studies suggest that it may play a role in Vc regulation through changes in pulmonary vascular tone. The purpose of this study was to examine the effect of exogenous dopamine and dopamine receptor‐2 (D2‐receptor) blockade on DLCO, Vc and Dm at baseline and during cycle exercise, as well as time‐to‐exhaustion at 85% of V̇O2 peak . We hypothesized that dopamine would increase DLCO, Vc, Dm and time‐to‐exhaustion, while D2‐receptor blockade would have the opposite effect. We recruited 14 young, healthy, recreationally active subjects (V̇O2 peak 45.8 ± 6.6 ml kg−1 min−1). DLCO, Vc and Dm were determined at baseline and during exercise at 60% and 85% of V̇O2 peak under the following randomly assigned and double blinded conditions: (1) intravenous saline and placebo pill, (2) intravenous dopamine (2 µg kg−1 min−1) and placebo pill, and (3) intravenous saline and D2‐receptor antagonist (20 mg oral metoclopramide). Exogenous dopamine and dopamine blockade had no effect on DLCO, Vc and Dm responses at baseline or during exercise. Dopamine blockade reduced time‐to‐exhaustion by 47% (P = 0.04), but intravenous dopamine did not improve time‐to‐exhaustion. While dopamine modulation did not affect DLCO, Vc or Dm, the reduction in time‐to‐exhaustion with D2‐receptor blockade suggests that endogenous dopamine is important for exercise tolerance.

Pulmonary diffusing capacity to nitric oxide and carbon monoxide during exercise and in the supine position: a test–retest reliability study

“…The present study is the first to assess and compare the reliability of D LCO/NO metrics during exercise to the resting supine position. We Coffman et al, n.d.;Jorgenson et al, 2018) and the mF IO 2 technique (Michaelchuk et al, 2019;Tedjasaputra et al, 2016).…”

“…These changes largely agree with findings from previous studies on healthy volunteers at various moderate to vigorous exercise intensities, based on both the D LCO/NO technique (Alves et al., 2022 ; Coffman et al., n.d . ; Jorgenson et al., 2018 ) and the technique (Michaelchuk et al., 2019 ; Tedjasaputra et al., 2016 ).…”