Fluid and electrolyte hormonal responses to exercise and acute
plasma volume expansion.
Grant, S. M., H. J. Green, S M. Phillips, D. L. Enns, and J. R.
Sutton.
Department of Kinesiology, University of Waterloo, Waterloo,
Ontario, Canada N2L 3G1 and Exercise Research Centre, Department of
Biomedical Sciences, The University of Sydney, Sydney, N.S.W.,
Australia
APStracts 3:0397A, 1996.
To investigate the effect of acute, graded increases in plasma volume
(PV) on fluid and regulatory hormone levels, 8 untrained males
(O2max, 45.2+/-2.2 ml/kg/min) performed prolonged cycle exercise
(46+/-4% O2max) on three occasions; namely with no PV expansion (CON)
and following 14% (LOW) and 21% (HIGH) expansions. The exercise
plasma levels of aldosterone (ALDO), arginine vasopressin (AVP) and
atrial natriuretic peptide (ANP) were all altered by acute PV
increases. A pronounced blunting (P < 0.05) of the ALDO response
during exercise was observed, the magnitude of which was directly
related to the amount of hypervolemia (CON < LOW < HIGH).
At 120 min of exercise, ALDO concentrations (pg/ml) were 660+/-71,
490+/-85 and 365+/-78 for CON, LOW and HIGH conditions respectively.
In contrast, the lower AVP and the higher ANP observed during
exercise appeared to be due to the effect of PV expansion on resting
concentrations. Since osmolality did not vary between conditions, the
results indicate that PV represents an important primary stimulus in
the response of ALDO to exercise. The lower exercise blood
concentrations of both epinephrine and norepinephrine observed with
PV expansion would suggest that a lower sympathetic drive may be
implicated at least in the lower ALDO responses.
Received 31 January 1996; accepted in final form 30 July 1996.
APS Manuscript Number A105-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 August 1996