CHILLING INJURY IN THE HOUSEFLY - EVIDENCE FOR THE ROLE OF OXIDATIVE STRESS BETWEEN PUPARIATION AND EMERGENCE

The hypothesis that oxidative stress plays a role in chilling injury i n the housefly was investigated by determining the effect of chilling on two important components of the insect's antioxidant defense system : (i) the superoxide anion scavenging enzyme, superoxide dismutase, an d (ii) the tripeptide, glutathione, which is significant in maintainin g the cellular redox status of the cell. The observations that led to this hypothesis are: (i) the housefly exhibited an U-shaped curve in O -2 consumption rate during development at 28 degrees C from pupariatio n to the pharate adult stage when sampled at 24-h intervals and (ii) O -2 consumption rates of these different age groups prior to chilling w as negatively correlated to the time after acute transfer to 7 degrees C required to observe a 50% reduction in adult emergence (LT(50)s) af ter their return to 28 degrees C. Superoxide dismutase (SOD) activity changed during this period of development at 28 degrees C in an invert ed U-shaped manner and was positively correlated to their LTS,s when a cutely transferred and stored at 7 degrees C. The SOD activity increas ed in the 12-24 h and 36-48 h postpupariation age groups at 7 and 10 d egrees C compared to the activity prior to chilling (Day 0). The 60-72 h postpupariation group and older showed initial reductions in SOD ac tivity during cold storage when compared to Day 0. Total glutathione ( GSH and GSSG) in the different age groups was typically decreased by c old storage. The percentage loss of glutathione in the different age g roups after 7 days at 7 degrees C was negatively correlated to their L T(50)s at 7 degrees C. The significance of these changes in SOD activi ty and glutathione levels to chilling injury in the housefly is discus sed. (C) 1996 Academic Press, Inc.