Role of Arsenic on the Regulation of Glycogen Metabolism in Liver of Taki Fishes (Channa Punctatus) Exposed to Cold

Liver is the major organ involved in the regulation of metabolic functions. Environmental and chemical effects are the stimuli regulating metaboilc activities. To clarify the regulation of glycogen metabolism in liver, Channa Punctatus varieties of fishes were exposed to low temperature (4~8C) since these species of fishes are highly energetic and survive in the critical situations. In response to cold for 30 min, 1, 2 and 4 h, liver glycogen were 1.37 ± 0.14 mg, 0.469 ± 0.13 mg, 1.40 ± 0.46 mg, 1.18 ± 0.22 mg respectively while for control fishes, the value was 1.80 ± 0.26 mg g of tissue weight. Glycogen content was significantly reduced in response to cold. However, higher response (approx. 3.8 folds) was observed after 1 h exposure. Glucose released in liver was similarly reduced in response to cold exposure. The findings indicate that cold exposure is involved in the regulation of glycogenolysis in liver. For further clarification of regulation of glycogen metabolism, groups of fishes were exposed to Na2HAsO4 as well as given cold exposure. Glycogen content and glucose released in liver were significantly increased in presence of 10 mM Na2HAsO4 for 1 and 2 h compared to the respective cold-exposed fishes. However, higher response was observed in 2 h demonstrating the inhibitory effect of Na2HAsO4 on glycogenolysis. Groups of fishes exposed to arsenic and cold had increased glycogen and glucose released than the arsenic treatment alone showing the additive effects of cold exposure on glycogenesis in liver. On the other hand, whenever the fishes were exposed to 100 mM Na2HAsO4, glycogen content and glucose released were significantly reduced in 1 h and the effects were more pronounced for 2 h treatment. The results demonstrate that higher concentration of arsenic causes glycogenolysis. Fishes exposed to arsenic and cold for 1 and 2 h had similar significant reducing effects on glycogen content as well as glucose released in liver. Our investigations demonstrate that increased glycogenolysis in liver might be a contributory factor for survival of these species of fishes in the environment and arsenic is involved in the modulation of cold-induced liver glycogen metabolism.