Concentration dependent function of superoxide dismutase in oxygen free radicals mediated tissue injury in renal brush border membrane.

: The dose dependent effect of superoxide dismutase in providing protection against oxygen free radicals mediated tissue damage was investigated. Xanthine-xanthine oxidase system was used to generate oxygen free radicals in vitro and damage renal brush border membrane of mice. At lower concentrations, superoxide dismutase was found to rather aggravate renal brush border membrane damage as shown by significant increase (p less than 0.05) in the malondialdehyde levels and corresponding decrease (p less than .05) in the activities of marker enzymes of renal tissue injury i.e. alkaline phosphatase, gamma-glutamyl transpeptidase and leucine aminopeptidase except maltase whose activity increased correspondingly. At higher doses of superoxide dismutase, significant protection (p less than .05) was observed against tissue damage in a dose dependent manner. On the other hand, catalase and mannitol provided dose dependent protection and their combinations with superoxide dismutase could alleviate the enhanced tissue damage produced by lower doses of superoxide dismutase. The implications of these findings have been discussed.