Varying atmospheric temperatures invariably induce thermal stress in the silkworm, Bombyx mori, which influence the functionality of aspartate aminotransferase (AST) and alanine aminotransferase (ALT). Thus, we have investigated AST and ALT activity in the new bivoltine lines (NBL). Interestingly, day-3 fifth instar larvae of NBL-5 being more susceptible to the thermal stress of 45°C showed highest level of AST (11.64 μm/mL) and ALT (9.83 μm/mL) activity in their hemolymph. Consequently, on day-5, AST (3.54 μm/mL) and ALT (1.39 μm/mL) activity were lower than day-3. Comparatively, between NBL and its parental breeds, the AST and ALT activity were found to be higher in day-3 (12.41 and 10.90 μm/mL) and day-5 (4.02 and 1.69 μm/mL) larvae of CSR2, while it was 12.93 and 10.14 μm/mL in CSR27 on day-3, and 4.31 and 2.03 μm/mL on day-5, respectively. This salient finding validates the linkage between the rate of cytotoxicity and AST and ALT enzyme activity in relation to the thermotolerance in NBL and its parents. Thus, the silkworm larvae can be considered as a model system for rapid evaluation of cytotoxicity and varied levels of AST and ALT activity as one of the biomarkers to correlate well with the tolerance level to critical temperature.
Key words: Bombyx mori; thermal stress; haemolymph; aspartate aminotransferase; alanine aminotransferase
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