Comparison of superoxide dismutase gene expression and activity in the hearts of spontaneously hypertensive and normotensive rats

Background: Recent studies have suggested that oxygen free radicals (OFRs) play a role in the pathogenesis of hypertensive vascular disease. Superoxide dismutase (SOD) is a naturally existing antioxidant, which plays an important role in scavenging OFRs. In order to determine if changes in superoxide dismutase (SOD) expression in the heart occur in the hypertensive state, the present study compared SOD in spontaneously hypertensive rats (SHRs) with normotensive rats. Methods: We measured the enzyme activities and mRNA levels of two main subtypes of SOD (Mn-SOD and CuZn-SOD) in hearts of 6-week, 9-week and 12-week-old SHRs and compared them with that of age-matched, normotensive Wistar-Kyoto (WKY) rats. Results: Higher levels of both Mn-SOD activity (55.9 ± 0.8 vs 33.6 ± 0.4 μ/mg protein, p <0.001) and Mn-SOD mRNA expression (195 ± 50% vs 99 ± 37%, p <0.001) were found in hearts of SHRs compared to WKY rats. Mild elevation of CuZn-SOD activity of SHRs (31.9 ± 0.4 vs 27.3 ± 0.4 μ/mg protein, p <0.05) was noted, but there was no significant difference in mRNA level of CuZn-SOD in hearts of SHRs and WKY rats. Conclusion: Alternation of OFRs scavenging enzyme SOD may be an important factor in the vulnerability of the rat heart to OFRs, or it may be related to the pathogenesis of hypertension in this species.