TY - JOUR

T1 - Effect of exercise on epinephrine turnover in trained and untrained male subjects

AU - Kjær, Michael

AU - Christensen, N J

AU - Sonne, B

AU - Richter, Erik A.

AU - Galbo, H

PY - 1985

Y1 - 1985

N2 - The kinetics underlying plasma epinephrine concentrations were studied. Six athletes (T) and six sedentary males (C) were given intravenous infusions of 3H-labeled epinephrine, after which arterial blood was drawn. They rested sitting and bicycled continuously to exhaustion (60 min at 125 W, 60 min at 160 W, 40 min at 200 W, and 240 W to the end). Work time was 154 +/- 13 (SE) (T) and 75 +/- 6 (C) min. At rest, epinephrine clearance was identical [28.4 +/- 1.3 (T) vs. 29.2 +/- 1.8 (C) ml . kg-1 . min-1], but plasma concentration [1.42 +/- 0.27 (T) vs. 0.71 +/- 0.16 (C) nmol . l-1] and, accordingly, secretion [2.9 +/- 0.7 vs. 1.5 +/- 0.4 nmol . min-1] were higher (P less than 0.05) in T than C subjects. Epinephrine clearance was closely related to relative work load, decreasing from 15% above the basal level at 30% of maximal O2 uptake (VO2 max) to 22% below at 76% of VO2 max. Epinephrine concentrations increased much more with work intensity than could be accounted for by changes in clearance and were, at exhaustion, higher (P less than 0.05) in T (7.2 +/- 1.6) than in C (2.5 +/- 0.7 nmol . l-1) subjects despite similar glucose, heart rate, and hematocrit values. At a given load, epinephrine clearance rapidly became constant, whereas concentration increased continuously. Forearm extraction of epinephrine invalidated use of blood from a cubital vein or a hand vein arterialized by hot water in turnover measurements. During exercise, changes in epinephrine concentrations reflect changes in secretion rather than in clearance. Training may increase adrenal medullary secretory capacity.

AB - The kinetics underlying plasma epinephrine concentrations were studied. Six athletes (T) and six sedentary males (C) were given intravenous infusions of 3H-labeled epinephrine, after which arterial blood was drawn. They rested sitting and bicycled continuously to exhaustion (60 min at 125 W, 60 min at 160 W, 40 min at 200 W, and 240 W to the end). Work time was 154 +/- 13 (SE) (T) and 75 +/- 6 (C) min. At rest, epinephrine clearance was identical [28.4 +/- 1.3 (T) vs. 29.2 +/- 1.8 (C) ml . kg-1 . min-1], but plasma concentration [1.42 +/- 0.27 (T) vs. 0.71 +/- 0.16 (C) nmol . l-1] and, accordingly, secretion [2.9 +/- 0.7 vs. 1.5 +/- 0.4 nmol . min-1] were higher (P less than 0.05) in T than C subjects. Epinephrine clearance was closely related to relative work load, decreasing from 15% above the basal level at 30% of maximal O2 uptake (VO2 max) to 22% below at 76% of VO2 max. Epinephrine concentrations increased much more with work intensity than could be accounted for by changes in clearance and were, at exhaustion, higher (P less than 0.05) in T (7.2 +/- 1.6) than in C (2.5 +/- 0.7 nmol . l-1) subjects despite similar glucose, heart rate, and hematocrit values. At a given load, epinephrine clearance rapidly became constant, whereas concentration increased continuously. Forearm extraction of epinephrine invalidated use of blood from a cubital vein or a hand vein arterialized by hot water in turnover measurements. During exercise, changes in epinephrine concentrations reflect changes in secretion rather than in clearance. Training may increase adrenal medullary secretory capacity.

KW - Adrenal Medulla

KW - Adult

KW - Epinephrine

KW - Humans

KW - Kinetics

KW - Male

KW - Physical Education and Training

KW - Physical Exertion

KW - Tritium

M3 - Journal article

C2 - 4055586

VL - 59

SP - 1061

EP - 1067

JO - Journal of Applied Physiology

JF - Journal of Applied Physiology

SN - 8750-7587

IS - 4

ER -