AJP - Regulatory, Integrative and Comparative Physiology, Vol 248, Issue 4 422-R425, Copyright © 1985 by American Physiological Society
Exercise training-induced hypervolemia in greyhounds: role of water intake and renal mechanisms
K. H. McKeever, W. A. Schurg and V. A. Convertino
The purpose of this study was to determine if the chronic hypervolemia that
accompanies endurance exercise training is due only to an increase in the
rate of water intake or if there were contributions from renal mechanisms.
Four greyhound dogs, previously sedentary for 3 yr, were utilized. During
the 28-day experiment each dog was trained on a treadmill ergometer for 14
consecutive days at 65% of its pretraining maximal work intensity. After
training, plasma volume increased 472 ml (27.5%, P less than 0.05). The
rate of water intake increased 328 ml/day (33%, P less than 0.05), whereas
urine output increased 87 ml/day (20.8%, P less than 0.05). The mean
resting 24-h values for clearance of sodium increased 0.29 ml/min (90.3%, P
less than 0.05), and clearance of potassium decreased 1.51 ml/min (16.1%,
NS). Glomerular filtration rate, free water clearance, and osmotic
clearance were not significantly altered. These data suggest that the
primary mechanism for the exercise training-induced hypervolemia in dogs is
a net positive water balance via increased water consumption without
significant contribution from an increase in renal water reabsorption.
