EFFECTS OF ACUTE EXERCISE AND PROLONGED EXERCISE TRAINING ON BLOOD-PRESSURE, VASOPRESSIN AND PLASMA-RENIN ACTIVITY IN SPONTANEOUSLY HYPERTENSIVE RATS

The purpose of this study was to investigate the effect of swimming training on systolic blood pressure (BP(s)), plasma and brain vasopressin (AVP), and plasma renin activity (PRA) in spontaneously hypertensive rats (SHR) during rest and after exercise. Resting and postexercise heart rate, as well as blood parameters such as packed cell volume (PCV), haemoglobin concentration (Hb), plasma sodium and potassium concentrations ([Na+], [K+]) osmolality and proteins were also studied. Hypophyseal AVP had reduced significantly after exercise in the SHR, whereas PRA had increased significantly in the Wistar-Kyoto (WKY) strain used as normotensive controls. Plasma AVP concentration increased in both strains. By the end of the experiment, training had reduced body mass and BP(s) by only 10% and 6%, respectively. Maximal oxygen uptake was increased 10% and plasma osmolality 2% by training. The postexercise elevation of heart rate was not significantly attenuated by training. A statistically significant reduction in postexercise plasma osmolality (10%) and [Na+] (4%) was observed. These results suggested that swimming training reduced BP(s). Plasma and brain AVP played a small role in the hypertensive process of SHR in basal conditions because changes in AVP contents did not correlate with those of BP(s). Moreover, there were no differences between SHR and WKY in plasma, hypophyseal and hypothalamic AVP content in these basal conditions. Finally, during moderate exercise a haemodilution probably occurred with an increase of plasma protein content. This was confirmed by the exercise-induced increase of plasma AVP and the reduction of hypophyseal AVP content, suggesting a release of this hormone, which probably contributed to the water retention and haemodilution. This investigation showed that swimming training produced an attenuation of the raised resting blood pressure in this strain and that plasma and brain AVP played a negligible role in the maintenance of hypertension in basal conditions. However, during training, this hormone may have played a role, training having induced simultaneously a decrease in BP(s) and plasma AVP.