Angiotensin converting enzyme inhibition and the norepinephrine
spillover response to dynamic exercise.
Leuenberger, Urs, Lawrence Gaul, Howard Noack, Steven Gubin, Robert
Zelis.
Division of Cardiology, Department of Medicine and the Department
of Cellular and Molecular Physiology, The Milton S. Hershey Medical
Center, The Pennsylvania State University College of Medicine
APStracts 3:0227A, 1996.
To determine if prejunctional angiotensin II receptors facilitate
norepinephrine (NE) release during exercise, normal volunteers
exercised at 25% or 65% of VO2max on two occasions. Steady state NE
kinetics were determined at rest and during exercise using infusions
of [3H]NE. Arterial plasma NE and [3H]NE were determined for
calculation of NE spillover and clearance. Before the second bout of
exercise at 25% VO2max later that day, enalaprilat (n=8) or
nitroprusside (n=5) were administered intravenously to lower blood
pressure to a comparable level, and saline was infused as a time
control (n=4). Exercise at 25% of VO2max increased heart rate form 73
to 110 beats/min, plasma NE from 296 to 626 pg/ml and NE spillover
from 1.56 to 3.32 nmol.min-1.[mu]-2. The exercise effect was
significant in each subgroup. At rest and during exercise the
decrease in blood pressure and the increase in plasma NE and NE
spillover were similar with enalaprilat and nitroprusside. There was
no drug effect in the saline group. In a separate group (n=7),
exercise at 65% of VO2max increased heart rate from 76 to 170
beats/min, plasma NE from 338 to 2656 pg/ml and NE spillover from
1.87 to 11.65 nmol.min-1.[mu]-2. In this group, 3 days of oral
enalapril did not affect the NE spillover response to exercise.
Because the angiotensin converting enzyme inhibitor did not attenuate
the NE spillover response to exercise, we conclude that at the
exercise levels tested, prejunctional angiotensin II receptors do not
appear to facilitate NE release.
Received 12 October 1995; accepted in final form 5 April 1996.
APS Manuscript Number A1104-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 8 May 96