Persistent sub-lethal chlorine exposure elicits the temperature induced stress responses in Cyprinus carpio early Wngerlings

Abstract

Thermal eZuents discharged through cooling systems of nuclear power plants often contain chlorine (used to control bio-fouling), which may aVect the metabolic status of Wshes. In order to evaluate the hypothesis, we tested the eVect of high temperature and a persistent sub-lethal chlorine exposure on stress responses in Cyprinus carpio advanced Wngerlings. Fishes were acclimated to four diVerent temperatures (26, 31, 33, and 36 °C) and maintained for 30 days in two diVerent groups. Subsequently, one of the groups was exposed to persistent chlorine (0.1 mg L¡1) for another 28 days and was compared with their respective temperature controls (without chlorine exposure). Sub-lethal doses of pollutants and increasing temperatures with in the tolerance range may not always register any morphological changes Therefore, we studied organ speciWc biochemical pathways viz. aspartate amino transferase, alanine amino transferase (enzymes of protein etabolism) in liver and muscle; fructose 1,6 diphosphatase (gluconeogenic pathway), in liver; pyruvate kinase, malate dehydrogenase, and lactate dehydrogenase (glycolytic pathway) in muscle; glucose-6-phosphate dehydrogenase (pentose phosphate pathway) in liver; alkaline phosphatase (phosphorus metabolism) in intestine, liver, and muscle; acetylcholine esterase (neurotransmitting enzyme) in brain, and adenosine triphosphate (for membrane transport) in gills at two diVerent acclimation periods (14 and 28 days). The results indicate that C. carpio Wngerlings demonstrated metabolic readjustments with increasing temperatures, in order to cope with energy demand of the cell. However, exposure to chlorine at higher temperatures aVected protein metabolism, gluconeogenic pathway and subsequently glycolytic pathway, leading to an energy-limited condition. In addition, alteration of membrane transport and neurotransmission might be an early indication of cellular damage. Overall results indicate that persistent sub-lethal chlorine exposure elicits temperature induced stress response in C. carpio early Wngerlings.