Changes in superoxide dismutase mRNA expression by streptozotocin‐induced diabetes

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Abstract
1 Experiments were designed to investigate the involvement of superoxide anions in the attenuated endothelium-dependent relaxation of the rat aorta from streptozotocin (STZ)-induced diabetic rats. 2 The endothelium-dependent relaxation responses to acetylcholine (ACh, 10−7 m) in helical strips of the aorta precontracted with noradrenaline (NA, 5 × 10−8∼3 × 10−7 m) were significantly decreased in STZ-induced diabetic rats. The recovery phase of the relaxation after single administration of ACh in the STZ-induced diabetic rats was more rapid than those in control vessels. 3 Preincubation of aortic strips with superoxide dismutase (SOD, 60 u ml−1) normalized the recovery phase of the relaxation of diabetic aorta after single administration of ACh, whereas catalase (150 u ml−1) or indomethacin (10−5 m) had no effects on the relaxation. 4 SOD (180 u ml−1) caused relaxation in NA precontracted aortic strips and the degree of the SOD-induced relaxation was significantly greater in diabetic aorta as compared with age-matched control vessels. 5 When the changes in mRNA expressions of Mn-SOD or Cu-Zn-SOD were observed, Mn-SOD mRNA expression was markedly decreased, and Cu-Zn-SOD was slightly decreased in diabetic aorta. 6 These results suggest that the rapid destruction of NO by superoxide anions may occur in the STZ-induced diabetic rats, and this may be due to a decrease in mRNA expression of Mn-SOD or Cu-Zn-SOD.