Disturbance of endogenous glucocorticoid levels by phenicol antibiotics in living fish

The wide present of phenicol antibiotics (PABs) in aquatic environments poses threats to aquaculture. Although PABs-induced adverse effects in fish have been reported, their influence on endogenous glucocorticoids (GCs) remain unknown. Herein, we developed an in vivo solid-phase microextraction (SPME) method to simultaneously monitor PABs and GCs in fish, thereby assessing the disturbance of GCs by PABs. By coupling to LC-MS/MS analysis, the method achieved great sensitivity (method detection limits ranging 0.0061–0.12 ng·g −1 ) and good reproducibility (RSDs of intra-/inter-fibers ＜10 %). The in vivo monitoring application showed PABs rapidly accumulated in fish with bioconcentration factors ranging 0.12–0.40. During exposure, the GC levels in fish were significantly elevated, in which cortisol (COL) consistently increased while corticosterone (COE) dropped to normal level after four days. PABs exposure induced elevated GC level, which subsequently enhanced the antioxidant defense system, leading to the mitigation of PABs-induced oxidative stress. During elimination, PABs were excreted and GCs, including COL and COE, returned to normal levels in only one day, with the stress responses and defenses subsided. These findings revealed the dual roles of GCs as stress indicators and adaptive regulators in fish under PAB exposure, and provided scientific support for developing aquaculture strategies in PABs contaminated waters. This study pioneered in in vivo simultaneous monitoring of exogenous and endogenous substances, facilitating future ecotoxicological investigations of emerging contaminants.