Journal of Applied Physiology, Vol 75, Issue 5 1946-1954, Copyright © 1993 by American Physiological Society
Swim training alters renal and cardiovascular responses to stress in borderline hypertensive rats
D. E. McCoy, J. E. Steele, R. H. Cox, R. L. Wiley and G. J. McGuire
Department of Zoology, Miami University, Oxford, Ohio 45056.
The present study assessed the effects of 40 min of tail shock stress (1-s
shock, 0.2 mA every 30 s) on renal and cardiovascular function in
swim-trained (T), water-immersed (IM), and untrained (UT) borderline
hypertensive rats (BHR). T BHR swam for 2 h/day 5 days/wk for 10-12 wk,
whereas IM BHR on the same schedule were placed in water at neck level and
were not permitted to swim. Age-matched sedentary controls were paired one
each with the exercise group (group 1) and the immersion group (group 2).
Heart rate was significantly greater in UT than in T BHR (P = 0.09) during
baseline (rest). Heart rate responses during stress were not different
between UT and IM BHR (group 2). Systolic and diastolic blood pressures
during stress and recovery were not different between UT BHR and T or IM
BHR. Urine flow rate was significantly increased from baseline during the
first 20 min of stress in UT and IM BHR only. Changes in glomerular
filtration rate were not consistent across studies. Renal blood flow
decreased significantly from baseline during tail shock stress in UT but
not T BHR. Plasma glucose levels were significantly increased above
baseline during the second 20 min of stress in UT BHR only and were
significantly greater than those in the T BHR. Plasma insulin levels in UT
BHR were significantly decreased from baseline during tail shock stress and
recovery but were unchanged from baseline in T BHR. These observations
suggest that swim training independent of water immersion alters the effect
that stress exerts on renal and cardiovascular function in BHR, which
results in better fluid and electrolyte conservation in T BHR.
