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

M.S. Haque
Department of Biochemistry and Molecular Biology, University of Rajshahi, Rajshahi-6205, Bangladesh

S.K. Roy
Department of Biochemistry and Molecular Biology, University of Rajshahi, Rajshahi-6205, Bangladesh

M.A. Islam
Department of Biochemistry and Molecular Biology, University of Rajshahi, Rajshahi-6205, Bangladesh

N. Roy
Department of Biochemistry and Molecular Biology, University of Rajshahi, Rajshahi-6205, Bangladesh

Abstract/ Executive Summary:

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 (4~8^oC) 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^-1 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.

Keywords: Peripheral tissue, Glycogenolysis, Sympathetic innervation, Cold exposure, Liver damage, Metabolic regulation

Location: Department of Biochemistry and Molecular Biology, University of Rajshahi, Rajshahi

Start Date:

End Date:

Program Area: Animal Health and Management

Commodity: Fish

Objectives:

To clarify the role of arsenic in coldinduced glycogen metabolism in Liver of Taki Fishes (Channa Punctatus) Exposed to Cold.

Methodology:

Fishes - Taki fish (Channa Punctatus) weighing 50 g to 60 g were used. They are maintained in normal water. In the day of experiment, cold exposure (4~8^oC) was given to the different groups of fishes in the cold chamber for 30 min, 1, 2 and 4 h period with full aeration and with free access of water. After cold exposure treatment, fishes were quickly decapitated and liver was sampled and kept at -20^oC. Control fishes were similarly used for sampling of tissues except giving cold exposure. Arsenic Treatment - Total 8 groups of fishes were used to examine the role of arsenic on the regulation of glycogen metabolism in response to cold exposure. The fishes were kept in different concentrations of arsenic compound (10 mM and 100 mM Na₂HAsO₄) and exposed to cold for 1 and 2 h in the cold chamber. The tissues were sampled similarly after the treatment. The respective other groups of fishes were treated with only 10 mM and 100 mM of arsenic compound (Na₂HAsO₄) for 1 and 2 h in ambient temperature. Assay of Glycogen and Glucose Released in Liver - Glycogen in liver was determined as described by Sawhney and Sing. Briefly, liver from each fish was taken in glass tube closed with cap and heated for 1 h with 2 mL of 30% KOH in boiling water bath and was cooled in ice. Four mL (2 volumes) of 95% ethanol was added to the tube and heated till the contents just started boiling and kept in cold for over night. The contents were centrifuged for 10 min at 8000 rpm. The ppt was collected, dissolved with 10 mL hot water and reprecipitated the extracted glycogen with 4 mL of 95 % ethanol. After centrifugation at 8000 rpm for 15 min, the precipitate was collected, washed two times with 65% ethanol (4 mL). The precipitate after centrifugation was dissolved with 2 mL of 2N H₂SO₄, boiled in water bath for 1.5 h for hydrolysis and was cooled by tap water. The hydrolyzed glycogen was neutralized with 6N NaOH using phenol red (1 or 2 drops). The volume was made up to 5 mL with water and was centrifuged again. The supernatant was used as the clear extracted glucose solution. For estimation of glycogen, aliquots were taken in tubes and measured glucose concentration by the laboratory manual. Statistical Analysis - Results of the experiments were expressed as mean and standard error of different groups. The differences between the mean values were evaluated by ANOVA followed by pared t-test with SPSS software.

Source of Information: Thai Journal of Agricultural Science 2009, 42(3): 159-166

Article Link (Online Journal): www.thaiagj.org

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

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. The 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.

Knowledge Management: Journal