The impact of nine weeks swimming exercise on heart function in hypertensive and normotensive rats: role of cardiac oxidative stress.

BACKGROUND: The purpose of this study was to estimate the effects of 9-week swimming training on cardiodynamic parameters and coronary flow in a rat model of high salt-induced hypertension with a special focus on the role of oxidative stress. METHODS: Rats involved in the research were divided randomly into four groups: healthy sedentary (SA), healthy trained (TA), sedentary hypertensive (SHA) and trained hypertensive animals (THA). Trained rats were exposed to 9-week swimming training (5 days/week, 60 min/day). Additionally, in order to induce hypertension animals from SHA and THA groups were on high sodium (8% NaCl solution) diet during 4 weeks. Afterwards all rats were sacrificed and hearts were isolated and retrogradely perfused according to Langendorff technique. The following parameters of cardiac function were continuously recorded: maximum and minimum rate of pressure development in left ventricle, systolic and diastolic left ventricular pressure and heart rate. Coronary flow was measured flowmetrically. Oxidative stress markers were determined in coronary venous effluent. RESULTS: Our findings demonstrated that 9 weeks of swimming training led to improvement of cardiac contractility, relaxation and systolic capacity of normotensive rats, while this training protocol induced enhanced diastolic function in hypertensive conditions. More pronounced effects of exercise in alleviating oxidative stress were observed in hypertensive rats. CONCLUSIONS: Obvious beneficial exercise-induced cardiac adaptations provide scientific basis for further researches which would thoroughly clarify the mechanisms through which swimming training alters myocardial function both in healthy conditions and in the presence of chronic diseases.