SUBLETHAL TOXICITY OF A DELTAMETHRIN-BASED INSECTICIDE IN RAINBOW TROUT, ONCORHYNCHUS MYKISS (WALBAUM, 1792) EMPHASIZING ON THYROID HORMONE RECEPTORS

Metrodesis, a deltamethrin containing commercial formulation has been extensively used in Turkey, in the framework of integral pest management thanks to its target-specific toxicity. So as to assess the potential impacts of Metrodesis (EC; active ingredient 25 g/L of deltamethrin) on thyroid hormone (TH) homeostasis of rainbow trout (Oncorhynchus mykiss); mRNA levels of thyroid hormone receptors (TRs), TR alpha and TR beta, were determined by RT-PCR soon after sublethal administration in a static bio-assay system. The sublethal dose of 4.15 mu g/L (1/4 of LC50 value) led to induction of relative expression levels of TR alpha and TR beta genes both in muscle and liver tissues, provided that TR alpha expression quantities were considerably higher than TR beta, although the differences were found statistically insignificant (P>0.05). Results of this study revealed an endocrine interaction between deltamethrinbased formulation and TH homeostasis corroborating previous researches that approved deltamethrin as an endocrine disrupting compound.