Toxicological effects of clofibric acid and diclofenac on plasma thyroid hormones of an Indian major carp, Cirrhinus mrigala during short and long-term exposures

• Globally, pharmaceutical drugs namely clofibric acid and diclofenac are commonly detected in water.
• Aquatic contamination by pharmaceutical drugs is an important issue and emerging as a new environmental problem.
• We analyzed the toxicity of clofibric acid and diclofenac in an Indian major carp, Cirrhinus mrigala.
• Both the drugs (1, 10 and 100 μg L−l) induced alterations in the thyroid hormones.
• These parameters could be used as biomarkers for pharmaceutical toxicity to fish.

In the present investigation, the toxicity of most commonly detected pharmaceuticals in the aquatic environment namely clofibric acid (CA) and diclofenac (DCF) was investigated in an Indian major carp Cirrhinus mrigala. Fingerlings of C. mrigala were exposed to different concentrations (1, 10 and 100 μg L−1) of CA and DCF for a period of 96 h (short term) and 35 days (long term). The toxic effects of CA and DCF on thyroid hormones (THs) such as thyroid stimulating hormone (TSH), thyroxine (T4) and triiodothyronine (T3) levels were evaluated. During the short and long-term exposure period TSH level was found to be decreased at all concentrations of CA (except at the end of 14th day in 1 and 10 μg L−l and 21st day in 1 μg L−l) whereas in DCF exposed fish TSH level was found to be increased when compared to control groups. T4 level was found to be decreased at 1 and 100 μg L−l of CA exposure at the end of 96 h. However, T4 level was decreased at all concentrations of CA and DCF during long-term (35 days) exposure period. Fish exposed to all concentrations of CA and DCF had lower level of T3 in both the treatments. These results suggest that both CA and DCF drugs induced significant changes (P < 0.01 and P < 0.05) on thyroid hormonal levels of C. mrigala. The alterations of these hormonal levels can be used as potential biomarkers in monitoring of pharmaceutical drugs in aquatic organisms.