Acute and chronic toxicity assessment and the gene expression of Dhb, Vtg, Arnt, CYP4, and CYP314 in Daphnia magna exposed to pharmaceuticals

The exposure of environment to pharmaceuticals disturbs the aquatic ecosystem. In this study,the effect of commonly used pharmaceutical compounds such as caffeine, ibuprofen, aspirin, and tetracycline has been investigated by the toxicity assay using Daphnia magna. The acute (48 h) and chronic (21 days) toxicity assays have been performed using Daphnia magna. The lethal concentrations of caffeine, ibuprofen, aspirin, and tetracycline with 50% mortality (LC50) have been determined as ∼445.3, 91.5, 310, and 90.8 mg/L, respectively. In the chronic toxicity test, low concentrations such as 1%, 2%, 10%, 20% LC50 of the pharmaceuticals were used to expose the organisms for 21 days. The effect of these pharmaceuticals on the molecular responses in the organisms has been studied from the gene expression level of five different biomarkers in Daphnia magna (Dhb, Vtg, Arnt, CYP4, and CYP314) after 48 h and 21 days exposure to the testing pharmaceuticals. The results show that five genes show different responsive patterns when Daphnia magna was under stressful conditions caused by caffeine, ibuprofen, aspirin, and tetracycline. During exposure to caffeine, only the response for the Dhb gene increased in the acute test, whereas all other genes, except Dhb gene, were down regulated in the chronic text. In contrast, in the acute and chronic toxicity test for ibuprofen, the responses for Arnt and CYP4 genes were reduced, respectively. Moreover, after 48 h exposure to aspirin, all other genes, except the Dhb gene, were down regulated. In the chronic test using tetracycline, five genes expression of D. magna were affected.