Biochemical characteristics of rat superoxide dismutase and the effect caused by paraquat injection on the enzyme activity in various tissues

Abstract

1. 1. Rat superoxide dismutase (SOD) prepared from the rat was not found by sedimentation in sucrose gradients or isolectric focusing to consist of more than one molecular form. On polyacrylamide gels, however, one major and one minor activity form could be demonstrated. 2. 2. The sedimentation constant and corresponding molecular weight of the enzyme determined by sucrose gradient centrifugation were found to be 3.0 ± 0.36 (34,300 ± 4023) and the isoelectric point 4.75. 3. 3. These characteristics were not found to differ for SOD prepared from different rat tissues and were not affected by a single dose of 40 mg/kg paraquat given subcutaneously 48 hr prior to sacrifice. 4. 4. The protein contents of various tissues based on both wet and dry weight were not found to deviate from normal during 5 days following a single exposure of paraquat up to 40 mg/kg. 5. 5. Experiments based on SOD activity measurements in different tissues as a function of time following single exposures of paraquat, revealed the presence of a very high induction capability of the SOD protein in the rat. The results have been correlated to autoradiographic studies. A correlation between SOD induction and tissues showing high paraquat retention could be demonstrated. This was especially expressed for the lung. 6. 6. Due to difference in the induction pattern following exposure to 5 and 10 mg/kg paraquat, respectively, it has been suggested that the ability of the rat to bear paraquat loads might be related to the SOD induction capability in various tissues.