SWIM TRAINING ALTERS RENAL AND CARDIOVASCULAR-RESPONSES TO STRESS IN BORDERLINE HYPERTENSIVE RATS

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 lev el and were not permitted to swim. Age-matched sedentary controls were paired one each with the exercise group (group 1) and the immersion g roup (group 2). Heart rate was significantly greater in UT than in T B HR (P = 0.09) during baseline (rest). Heart rate responses during stre ss were not different between UT and IM BHR (group 2). Systolic and di astolic blood pressures during stress and recovery were not different between UT BHR and T or IM BHR. Urine flow rate was significantly incr eased from baseline during the first 20 min of stress in UT and IM BHR only. Changes in glomerular filtration rate were not consistent acros s studies. Renal blood flow decreased significantly from baseline duri ng tail shock stress in UT but not T BHR. Plasma glucose levels were s ignificantly increased above baseline during the second 20 min of stre ss in UT BHR only and were significantly greater than those in the T B HR. 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 inde pendent of water immersion alters the effect that stress exerts on ren al and cardiovascular function in BHR, which results in better fluid a nd electrolyte conservation in T BHR.