Thyroid Hormone Modifies the Metabolic Response of Air-Breathing Perch (Anabas testudineus Bloch) to Nimbecidine Exposure

The action of thyroid hormones on metabolite regulation of nimbecidine-exposed climbing perch was studied to understand the role of these hormones in tolerance mechanisms of fish to nimbecidine exposure. Anabas testudineus, the climbing perch, was treated with nimbecidine, a neem-based biopesticide, at nominated concentrations (60 and 600 μgL^-1) for 48 h, with or without THs, and the levels of triiodothyronine (T₃) and thyroxine (T₄), metabolite and nucleic acid were quantified. The treatment of THs along with nimbecidine produced a different metabolite pattern. A significant rise in serum T₃ occurred in the nimbecidine-treated fish but the serum T₄ level remained unaffected. Nimbecidine exposure increased the serum triglycerides and the serum urea but the serum glucose and liver total protein, RNA and DNA remained unchanged. Significant reduction in the aspartate aminotransferase and alkaline phosphatase activities occurred in the serum and liver of nimbecidine-treated fish but the lactate dehydrogenase and alanine aminotransferase activities remained unaffected. The data indicate that TH modifies the metabolite pattern of climbing perch during its exposure to nimbecidine and, thus, suggest that TH is involved in the mechanism of stress tolerance in fish.