Abstract

  A recent approach to evaluate environmental induced damages has been damages has been suggested, based on the stress response. The approach involves the detection of stress protein induction in organisms to infer about environmental conditions in their surroundings. However, to be an indicator of adverse biological effects in the environment, the elevation of stress proteins should be compared to a response pattern for the experimental species. Juvenile Corbicula fluminea, collection from a control site, were submitted to heat-shock stress in the laboratory to obtain the stress response pattern under normal and extreme conditions. Acclimated to 26°C, the specimens were submitted to 29, 32, 35 and 38°C, for 96 h. After 1,2,4, 8, 24, 48,72 and 96 h of exposure, clams were removed from each vial and prepared for stress protein analysis. Animals from the control site were frozen in liquid nitrogen at the time of collection, and prepared for stress protein analysis. Hsp6O and 70 were detected by immunoreactivity after separation on 12.5% polyacrylamide gels and transference to nitrocellulose by western blotting, to determine the stress protein concentrations. The result showed that hsp7O increased at 4 h from the beginning of the experiment and progressed over the 96 h experimental period in animals exposed to 35°C. However hsp70 levels decreased between 4 h and 24 h for the clams stressed at their lethal temperature of 38°C. Immunoblotting with hsp60 showed similar reactivity. At 38°C there was an increase in the amount of hsp60 at 4 h, reaching a maximum eight-fold level at 8 h. By 96 h, the amount decreased to levels lower than those observed at 4 h. At 38°C the level of hsp6O began to decrease at S h and continue to decline to 24 h when the clams died. The data support the hypothesis of increasing concentrations of stress protein until the heat shock approaches the thermal limits for the species. The results of this research suggest the usefulness of using the stress response as a diagnostic in environmental toxicology. They confirm that the sps response may serve as a valid biomonitoring tool under chronic, sublethal exposures when it is still possible to prevent effects at organismal or higher organizational levels.

Keywords: stress proteins, Corbicula fluminea, stress response