Expressions of iNOS and Superoxide Dismutase in the Skeletal Muscle of the Spontaneously Hypertensive Rat after Ischemic-preconditioning

Lee, Jun Hee; Seo, Youn Kyoung; Paik, Doo Jin

Abstract

A balance between production and degradation of reactive oxygen species has an important role in the cardiovascular homeostasis, and is known to contribute to hypertension. Under oxidative stress, an upregulation of inducible NOS (iNOS) induces ischemic-reperfusion injury, and is involved in the pathophysiology of the hypertension. Ischemic-reperfusion injury of the skeletal muscle results from reactive oxygen species, and overexpression of iNOS in the skeletal muscle increases the ischemic injury. Superoxide dismutase (SOD), antioxidant, is a major enzyme for degradation of reactive oxygen species (ROS). The purpose of this study was to observe the effect ischemic preconditioning (IP) of the lower limb on the expression of iNOS, CuZnSOD and MnSOD in the white and red muscle of the spontaneously hypertensive rat (SHR). Nine weeks old male normotensive rat (Wistar-Kyoto rat, WKY) and SHR were divided into control and IP groups. The IP group was further divided into 3 (3IP) and 10 (10IP) times of IP. Left common iliac artery was occluded 3 and 10 times for 5 min of ischemia-5 min of reperfusion using rodent vascular clamp. The animals were sacrificed at 0, 0.5, 1, and 3 hours after reperfusion and the Tibialis anterior and Soleus were removed. The expressions of iNOS, CuZnSOD and MnSOD in the skeletal muscle were examined with immunohistochemical methods and Western blot analysis. iNOS was expressed in Tibialis anterior, but in Soleus after IP. The expression of iNOS was increased in both WKY and SHR, it was higher in SHR than WKY. CuZnSOD and MnSOD were expressed in Tibialis anterior and Soleus, higher in Soleus, after IP. The expression of CuZnSOD and MnSOD were increased in both WKY and SHR, higher in WKY than SHR. It is consequently suggested that hypertensive individual and white muscle are more sensitive to ischemic injury of the skeletal muscle as considering their high expression of iNOS and low expression of SODs.