Superoxide dismutase activities in long-lived Drosophila melanogaster females: Chico¹ genotypes and dietary dilution

Superoxide dismutase (SOD) activities were determined for dietary dilution conditions that extend the life span of Drosophila melanogaster. The hypothesis motivating this research was that elevated SOD activity is associated with increased life span resulting from flies being held on a restricted diet. SOD activities were also measured for chico¹ which is a mutation in the insulin receptor substrate protein gene associated with life span extension. This allowed us to confirm the results of (Clancy et al. 2001) and extend the results by measuring CuZn SOD and Mn SOD activities in addition to the previously determined overall SOD activity. If the same form of SOD activity (CuZn SOD or Mn SOD) was elevated on the dilute diet that extends life span and in the long lived chico¹ homozygotes, then it would suggest that life span extension by dietary restriction and by insulin signaling mutations has a similar underlying mechanism. However, overall SOD activity, and CuZn SOD or Mn SOD activities did not differ among the diets tested. As observed previously (Clancy et al. 2001), overall SOD activity was elevated in chico¹ homozygotes compared to the heterozygote or wild type. Results from the present study indicate that elevated CuZn SOD activity, not Mn SOD, is the basis for the relatively high level of SOD activity in the chico¹ homozygotes.