Effects of infused epinephrine on slow phase of O2 uptake kinetics during heavy exercise in humans

• Published in: Journal of applied physiology (1985) Vol. 77; no. 5; p. 2413
• Main Authors: Gaesser, G A, Ward, S A, Baum, V C, Whipp, B J
• Format: Journal Article
• Language: English
• Published: United States 01.11.1994
• Subjects: Adult; Animals; Blood Gas Analysis; Chromatography, High Pressure Liquid; Epinephrine - administration & dosage; Epinephrine - blood; Epinephrine - pharmacology; Exercise - physiology; Humans; Infusions, Intravenous; Lactates - blood; Lactic Acid; Male; Mass Spectrometry; Oxygen Consumption - drug effects; Oxygen Consumption - physiology; Pulmonary Gas Exchange - drug effects; Respiratory Function Tests
• ISSN: 8750-7587
• DOI: 10.1152/jappl.1994.77.5.2413

We tested the hypothesis that infused epinephrine (Epi) would augment the slow phase of oxygen uptake (VO2) during heavy exercise. Six normal healthy males initially performed a ramp test on a cycle ergometer to estimate the lactate threshold (LT) and determine peak VO2. Each subject then performed two 20-min constant-load tests at a power output calculated to elicit a VO2 equal to estimated LT + 0.2(peak VO2--estimated LT) under control conditions throughout and with an intravenous infusion of Epi from minutes 10 to 20 at a rate of 100 ng.kg-1.min-1. Pulmonary gas exchange variables were determined breath by breath. Arterialized venous blood was repeatedly sampled from the dorsum of the heated hand. Epi infusion elevated (P < 0.05) plasma Epi concentration (i.e., from 420 +/- 130 pg/ml at minute 10 to 2,190 +/- 410 pg/ml at minute 20) but had no effect on plasma norepinephrine or K+ concentrations. Concentrations of blood lactate and pyruvate were increased, pH was decreased, and base excess became more negative by infusion of Epi (P < 0.05). Epi infusion increased (P < 0.05) CO2 production and the respiratory exchange ratio but had no effect on ventilation or VO2. VO2 increased (P < 0.05) to the same extent in both control (3.14 +/- 0.12 l/min at minute 10, 3.28 +/- 0.12 l/min at minute 20) and Epi infusion (3.10 +/- 0.11 l/min at minute 10, 3.25 +/- 0.11 l/min at minute 20) trials. We therefore concluded that neither Epi nor its associated humoral consequences contribute significantly to the slow phase of VO2 kinetics during heavy exercise.