Effects of moderate treadmill activity on cardiovascular factors in spontaneously hypertensive rats.

Abstract

Hypertension is a major health problem throughout the world because of its high prevalence and its association with increased risk of cardiovascular disease. Oxidative stress due to either increase of reactive oxygen species (ROS) or a compromised antioxidant status has also been positively correlated with cardiovascular diseases. The beneficial effect of physical activity has been well documented in the literature but studies have shown that in the SHR physical activity leads to oxidative stress. The SHR is an excellent model of essential hypertension and hence the present study was designed to investigate the effect of moderate treadmill activity on various cardiovascular factors in SHR. Sixteen male SHR and male Wistar rats (n=16) weighing between 70 and 90 g were used and they were randomly divided into four groups: The SHR exercised group (n=8), Wistar exercised group (n=8), SHR group (n=8) and Wistar (n=8). All the rats in exercised group were subjected to a weekly increase in the rate of activity on the treadmill. Blood pressure, blood glucose and body mass were recorded weekly. At the end of the 8 week experimental protocol, animals were fasted for 12 hours, anaesthetized with halothane and blood and tissue samples harvested. The C-reactive protein (CRP) and antioxidant-associated trace elements such as copper (Cu), iron (Fe), manganese (Mn), selenium (Se), and zinc (Zn) were measured in the blood, brain and skeletal muscle. Cardiotrophin-1 (CT-1) was determined in the plasma, total antioxidant capacity (TAC) and malonyldialdehyde (MDA) were determined in blood and skeletal muscle, plasma TAC levels was also measured. The superoxide dismutase (SOD), IkB and nuclear factor-kappa (NF-kB) gene expression were also measured in skeletal muscle and liver. Kidney sections were stained with Haematoxylin-Eosin (H&E) and sections of aorta were stained with Verhoeff-van Gieson (VVG). The results show that physical activity did not significantly change both the systolic and diastolic blood pressures in SHR. Plasma levels of CRP and NF-kB mRNA expression were increased in both SHR and Wistar exercised groups. An increase in oxidative stress due to physical activity was evident by an increase in TAC and MDA levels in the skeletal muscle. A significant decrease in blood TAC and SOD mRNA expression was also evident in the SHR exercise group. Physical activity also resulted in significant shifts in trace elements that are associated with a compromised antioxidant system.