Pharmacokinetics, Withdrawal Time, and Physiological Effects of Single Oral Administration of Enrofloxacin in Dybowski’s Frog (Rana dybowskii)

<b>Background</b>: As a broad-spectrum fluoroquinolone, enrofloxacin (ENR) is commonly employed to manage bacterial infections in aquatic species. Nevertheless, there have been no documented pharmacokinetic and residue studies conducted on Dybowski's frog (<i>Rana dybowskii</i>). Therefore, the objective of our study was to characterize the pharmacokinetics (PK) of ENR and its metabolite ciprofloxacin (CIP) in <i>R. dybowskii</i>, establish withdrawal times, and evaluate the physiological effects associated with ENR administration. <b>Methods</b>: Adult <i>Rana dybowskii</i> (120 individuals; 60 males and 60 females) were sex-separated and acclimated in four tanks. Prior to dosing, three males and three females were randomly selected as untreated controls (without ENR administration). Following the oral gavage of ENR (10 mg/kg), blood, liver, and kidney tissues were collected at 0.25, 0.5, 1, 1.5, 2, 4, 6, 8, 12, 24, 36, 48, and 72 h (n = 6) for pharmacokinetic analysis. Muscle and oviduct tissues were additionally sampled at 1, 3, 7, 15, and 30 days post-dose (n = 6) for ENR content determination. Serum/tissue ENR concentrations were measured via Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) and analyzed using a non-compartmental model (WinNonLin 6.1 software) to calculate PK parameters including peak time (T_max), peak concentration (C_max), and area under the curve (AUC_0-t). In studying the physiology effects of ENR administration, biochemical enzyme activities and gene expressions in the liver and intestine were assessed post-ENR administration. <b>Results</b>: ENR demonstrated rapid absorption and extensive distribution in <i>R. dybowskii</i>. The withdrawal periods were determined to be over 33 days for females and 34 days for males in <i>R. dybowskii</i>. Following ENR administration, there was an increase in immune enzymes (AKP (alkaline phosphatase) and ACP (acid phosphatase)) as well as glycolytic enzymes (HK (hexokinase), PK (pyruvate kinase), PFK (phosphofructokinase)). Antioxidant enzyme levels, specifically SOD (superoxide dismutase) and CAT (catalase), peaked at 1.5 h post-ENR administration but subsequently declined by the 8 h mark. Additionally, following ENR treatment, <i>IGF1</i>, <i>PI3K</i>, and <i>Akt</i> exhibited up-regulation, whereas <i>Keap1</i> and <i>GYS1</i> showed down-regulation. <b>Conclusions</b>: The administration of ENR at a dosage of 10 mg/kg significantly enhances the activities of AKP and ACP, promotes glycolysis, and activates the Keap1/Nrf2 and PI3K-Akt signaling pathways in <i>R. dybowskii</i>. These findings establish a foundation for the rational application of ENR and the determination of withdrawal times in frog aquaculture.