Endocrine disruption and altered biochemical indices in male Oncorhynchus mykiss in response to dimethoate

This study was conducted to investigate effects of dimethoate on biochemical indices of blood (alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase activity (ALP)) and endocrine system by using serum testosterone, 17β-estradiol and cortisol levels as well as organosomatic indices (hepatosomatic index (HSI) and gonadosomatic index (GSI)) as biomarkers in sexually mature male Oncorhynchus mykiss. Prominent elevation in ALT and AST activities was determined which proved to be significantly and positively correlated with exposure concentration and period. There was no conspicuous alteration in ALP enzyme activity. Dimethoate did not show any sign of anti-androgenic effect as assessed by unaltered testosterone level. The duration and concentration dependant induction in 17β-estradiol level was observed at 5 and 15 days which was followed by significant decline at 30 days. The cortisol level showed an increasing pattern throughout the exposure period. GSI remained unchanged while pesticide treatment led to a reduction in HSI which was more pronounced with extended exposure. Present results clearly indicate that dimethoate revealed its toxicity on liver tissue by impairing membrane permeability and it has an endocrine disrupting potential possibly via acting as an estrogen mimic and modifying feedback on the hypothalamo-pituitary axis as evidenced by concomitant alteration in 17β-estradiol and cortisol levels.

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► Dimethoate did not exert any anti-androgenic effect in O. mykiss.
► Dimethoate caused endocrine disruption by acting as an estrogen mimic.
► Increase in cortisol level was assumed as a general adaptive response.
► High transaminase activities can be explained via impaired membrane permeability.