Sex differences in renal oxidative stress in Spontaneously Hypertensive Rats

Abstract

Oxidative stress has been implicated in the development of hypertension in humans and animal models. Males have high blood pressure and exhibit more oxidative stress than do females. Previous studies of our laboratory have supported an important role for reactive oxygen species (ROS) in the maintenance of hypertension in spontaneously hypertensive rats (SHR). This study was performed to test whether there are sex differences in the expression and activity of enzymes involved in the pathways responsible for generation or metabolism of ROS in renal tissue. Kidneys from male and female SHR, 18 weeks old, were perfused clear of blood and subsequently removed and separated into cortex and medulla and homogenized. Lucigenin-enhanced chemiluminescence was used to determine basal and NADPH-stimulated superoxide production, an index of NADPH oxidase activity. Expression of catalase, superoxide dismutase and glutathione peroxidase was assessed using western blots. Female SHR exhibited higher basal superoxide in cortex (p=0.02) but higher NADPH-stimulated superoxide production (p=0.001) in the medulla. Catalase expression was lower (4.04 ± 0.4 vs. 1.64 ± 0.1, p=0.01) and superoxide dismutase higher in female renal cortex as compared to male. We found no sex differences in the expression of glutathione peroxidase in either cortex or medulla. These data suggest that the sex differences in oxidative stress could be the result of differently regulated pro- and anti-oxidant systems.