Bioconcentration, metabolism, and biomarker responses in marine medaka (Oryzias melastigma) exposed to sulfamethazine.

The antibiotic sulfamethazine (SM 2 ) is commonly used in agriculture and livestock for its broad-spectrum antibacterial properties. Due to its widespread application, SM 2 is frequently detected in surface water and sediments. The objective of this study was to investigate the bioconcentration, distribution and biomarker responses of SM 2 and its main metabolite, acetylated sulfamethazine (N-SM 2 ) in medaka ( Oryzias melastigma ). Two treated groups of medaka were exposed to concentrations of 40 μg/L and 200 μg/L of SM 2 for 24 h to simulate the habitual use of those antibiotics in aquiculture activities. SM 2 and its main metabolite, N-SM 2 , were measured in several tissues during the 24 h uptake period by UPLC/MS/MS. The bile exhibited the highest SM 2 concentration followed by the liver, gonad, gills, and muscle and the bioconcenration factor (BCF) was 10.69–42.95 in female fish and 2.78–145.36 in male fish. N-SM 2 showed a different distribution pattern from the parent compound, accumulating mainly in the gonad, and its BCF was much higher in the male group. Gender-related differences were also observed in the bioconcentration, transform rate and biomarkers of SM 2 . Biomarkers (SOD, CAT) in the liver changed significantly after 2, 12, and 24 h of exposure ( P < 0.05), and presented a double-peak phenomenon. These results indicated that SM 2 can be absorbed and metabolized through multiple routes by fish in a short time. Interactions between biological systems and SM 2 or its metabolites may induce biochemical disturbances in fish. [ABSTRACT FROM AUTHOR]