Thermal Effect On Tissue-specific Hsp70 Levels And Heat Stress Responses In Common Carp (Cyprinus Carpio)

Temperature has been recognized as an important factor that influences biological systems at numerous levels of organization. Many eurythermal fish have evolved a number of behavioural, biochemical and molecular mechanisms to assist in their continuous adjustment to naturally occurring temperature variation. When the water used to cool power plants is discharged into streams, rivers, and lakes, the addition of heat could stress some species including macrophytes, zooplankton, phytoplankton and fish residing in the receiving waters. This is known as thermal pollution or thermal discharge, which would cause thermal shock and directly interferes with physiological processes of the biota, such as enzyme activity, feeding, reproduction, respiration and growth. Recently, Studies into the effects of thermal discharges on heat shock response of fishes have been primarily focusing the change in heat shock or stress proteins (Hsps) expression with increasing temperature. Of all of the Hsps families that have been studied, the 70 kDa protein family (Hsp70) has been most widely used as a biomarker due to its rapid and significant increase during a wide range of environmental stressors. Temperature rising of lake or reservoir due to heated discharge from power plant will increases poisonousness of the toxicant materials and is harmful to aquatic lives.The present study investigated the expression of Hsp70 in heart, kidney, brain, gill, muscle, liver and serum of the common carp Cyprinus carpio both by thermal thermal influence exposure and in long-term heat discharge environment. The area under our field investigation was the Douhe Reservoir receiving thermal effluent, which produces a mean increase of 4°C in water. In laboratory exposure experiments, fish acclimated at 10℃or more were exposed to various elevated temperatures, or exposed to heat shock and phenol complex for 24h, or exposed to different manner thermal stress after 24-hour exposure to copper. Serum Hsp70 was analyzed using the sandwich Enzyme-Linked Immunosorbnent Assay (ELISA), and as other tissues Hsp70 expression by Western blots of one dimensional SDS-PAGE separation.In eco-toxicology and eco-chemistry, behavior enzyme and growth of living beings have been broadly taken as biomarkers, which were used to estimate the eco-toxic effect caused by thermal pollution. The experiment was to analyze how it would be change by different heat shock. Another way to study thermal tolerance is to determine a critical thermal maximum (CTM) defined as"the thermal point at which locomotor activity becomes disorganized and the animal loses its ability to escape from conditions that will promptly lead to its death". Moreover, the criterion of CTM based on lethal effects of hyperthermia does not meet ethical requests. As a consequence, the aim of the present study was to use our test to measure changes in CTM values. The results of this study demonstrate that these symptoms were much sensitive compared to CTM and median lethal concentration of toxicity. The behavioral of CLE (complete loss of equilibrium) was studied to be the best criterion to detecte CTM.Enzyme activities such as glutamate pyruvate transaminase (GPT), Glutamic Oxaloacetate Transaminase (GOT) and Catalase (CAT) of carps and crucians, and growth factor of goldfish were also studied. The result shows that there is remarkable relationship between the various heat stress and stress responses at diversified levels of fish, which could be used as the sensitive index for thermal influence. GOT of carps is sensitive to the thermal effect, and GPT to phenol. CAT will be a good director for the pollution. Results in carps are in agreement with these reports supporting the concept that the Hsp70 expression in response to heat shock may be more important in dealing with heat-induced damage in the tissue during adaptation. There were combined effects of temperature and poison on Hsp70 expression is certain tissues of carps. These tissues had different levels of Hsp70 responses to thermal influence both in acute exposure and long-term acclimation. Although explanation for this could be discrepancy, the pattern of the tissue Hsp70 expression may have a close relationship with the thermal tolerance of carps and allow them to survive long-term thermal pollution habitat.The results indicate that these tissues of C. carpio had different levels of Hsp70 responses to similar heat stress both in the field and in the laboratory, and the level of Hsp70 in kidney could be a good biomarker to assess the degree of thermal pollution. The tissue-specific pattern of Hsp70 expression may have a close relationship with the thermal tolerance of carps and allow them to survive long-term thermal pollution habitat.However, additional experiments are required which would employ a greater number of heat shock temperatures, different time exposures, and seasonal field study and would assess other physiological and biochemical characteristics to fully understand the mechanisms underlying the measured temperature-induced alterations of heat shock response (Hsp70).