THE EFFECTS OF EXERCISE TRAINING ON SALT-INDUCED HYPERTENSION IN THE BORDERLINE HYPERTENSIVE RAT

The borderline hypertensive rat (BHR) develops severe hypertension when chronically subjected to either a high salt diet or behavioral stress. Previous research has shown that daily exercise can attenuate the development of stress-induced hypertension in the BHR. The current study sought to determine whether exercise might also exert a similar protective effect on salt-induced hypertension. Two groups of BHR were placed on a high salt diet for 20 weeks; one of the groups also engaged in daily swim training for the entire 20 week period. A third group of BHR served as maturation controls. At the end of the experimental period, direct measurement of heart rate in conscious subjects revealed a significant resting bradycardia in the trained group on a high salt diet but no significant group differences with respect to blood pressure level. Cardiovascular responses to an episode of acute stress revealed that BHR are capable of elevating pressure in response to a novel stressor after swim training. These observations suggest that exercise may be an environmental intervention capable of increasing cardiovascular responses to acute stressors.