Essay --

Discussion In nature, there are a group of proteins which are known to produce a universal response that is the production of stress proteins namely heat shock proteins (Hsp70), expressed in response to external stimuli. They are expressed in normal state conditions hence aiding in the native polypeptides folding and its translocation to different cellular compartments (Feder and Hofmann, 1999; Hartl and Hartl-Meyer, 2002). Iwama et al. (2004) worked on whether Hsp70 are a molecular marker for indicating stressed states in fishes. Ammonia which is a common pollutant has been seen and known to interfere with cellular proteins and in turn interfere with amino acid homeostasis (Cooper and Plum, 1987). As a result of ammonia toxicity, Hsp70 protein gets enhanced and in turn helps in inducing proteotoxicity. Our observation proves that the ability of these fishes (M. cuchia) to tolerate such high concentration of NH4Cl is mainly due to the ability of Hsp70 to induce proteotoxicity, an ability to rep air partly denatured proteins caused due to ammonia toxicity. Similar observation of expression of Hsp70 was seen in brown trout (Salmo trutta f. fario) exposed to sub-lethal concentrations of ammonia (Luckenbach et al., 2003). Immunocytochemical analysis clearly demonstrated the localized expression of Hsp70 in liver, kidney and brain of M. cuchia during exposure to 50 mM NH4Cl for 7 days with a slight fall of expression in 14 days 50 mM NH4Cl tissues (Fig. X). Immunopositivity to Hsp70 antibody has been detected in control as well as in 7 and 14 days 50mM NH4Cl treated tissues. In the unstressed cells Hsp70 helps in maintaining cellular homeostasis (Fink and Goto, 1998). In liver, the expression of Hsp70 was more predominant in hepatic sin... ...l red skeletal muscle of paddleï ¬ sh. To add to our observation, Poltronieri et al. (2008) also found Hsp70 immunonegativity in control tissues of carp (Cyprinus carpio) and rainbow trout (Oncorhynchus mykiss) along with absence of immunopositivity in stressed states. The fall in immunoreactivity which was observed in 14 days of NH4Cl treated tissue might be mainly due to slight acclimatization at the end. Therefore, one needs to find out the possible implications of Hsp70 in this fish, M. cuchia, which is known to tolerate high ammonia concentrations. As Hsp70 is known to act as an important candidate for identification of stresses and also an important biomolecules acting as sentinels of contamination exposure, this stress proteins, Hsp70 might give a better understanding of how these fishes adapt themselves to such concentrations of environmental ammonia toxicity.