| Megalobrama amblycephala is an important freshwater fish in China. A High Performance Liquid Chromatography(HPLC) method was developed for the detection of OTC in plasma and tissues of M. amblycephala. The pharmacokinetics and residue depletion of OTC were conducted by this method in health M. amblycephala with a single oral administration, multidose oral administration for 5 days at 25 ℃.1. A simple and rapid method for the simultaneous and extraction and determination of OTC in plasma, liver, kidney, muscle of M. amblycephala was established. Agilent SB-C18(250 mm×4.6 mm i. d., 5 μm) reversed-phase column was used for the detection. The UV detector was set to 355 nm. The mobile phase was acetonitrile and Na H2PO4+EDTA(V : V = 22 : 78). Column temperature was 25 ℃. The flow rate was 0.5 m L/min. The results confirmed that the OTC analysis was rapidly performed. A linear relationship was developed over the range of 0.05–20.0 μg/m L, the correlation coefficient(R2) was greater than 0.999. The standard recovery rates of plasma were between 94.44%~96.07%, however, the standard recovery rates of tissues were between 86.01%~91.97%. The percentage relative standard deviations for inter-day and intra-day precisions were below 10%. The LODs were 0.014~0.02 μg/g for OTC in plasma and tissues.2. The pharmacokinetics of OTC were conducted in M. amblycephala after a single-dose and a multi-dose for 5 consecutive days of 100 mg/(kg·bw) at 25 ℃, as a result a one-compartment model was developed to describe the pharmacokinetics of OTC in M. amblycephala. At the same condition, the fish were fed with fodder which contained 1% OTC, the fish were fed at 1% of the mean bodyweight for 5 days, a two-compartment model was developed to describe the pharmacokinetics of OTC. the absorption half-life(t1/2(α))was 5.79, 9.40, 6.96, and 8.06 h in serum, liver, kidney, and muscle, respectively. The absorption half-life was 3.62, 7.33, 4.59, and 5.02 h with a multi-dose oral administration, the order of peak concentration(C max) with a single-dose and multi-dose was liver > plasma > kidney > muscle. The elimination half-time(t1/2(β))in plasma, liver, kidney, muscle was 58.63, 126.43, 65.10, and 58.85 h when M. amblycephala was treated with single-dose, the time changed to 91.75, 214.87, 126.22, and 135.84 h with a multi-dose oral administration. When M. amblycephala were fed with fodder which mixed with OTC, the absorption half-life(t1/2(α))was 0.62, 42.06, 11.17, 8.43 h, elimination half-time(t1/2(β))was 59.10 113.36, 123.32, 75.042 h in plasma, liver, kidney, muscle. The order of peak concentration(C max) was liver > kidney > plasma > muscle. The study showed that OTC absorbed much faster after a multi-dose than a single-dose. The OTC was found in all tissues with a lower bioavailability after M. amblycephala were fed with fodder that contained 1% OTC. The MIC of OTC in Aeromonas hydrophila is 0.5~2 μg/m L, the concentration is much lower than the peak concentration in plasma, which after a single and multi-dose. The concentration in plasma after fed with fodder is 0.6 ug/m L, which was a little higher than 0.5 ug/m L, so it is suggested that when the fish was fed with foder, the higher concentration of OTC should be added.3. The depletion of OTC in M. amblycephala muscle at 25 ℃ with an oral administration 100 mg/(kg·bw) were investigated. The fish were sampled at certain time. A withdrawal time of 26 days was necessary to ensure that the residues of OTC were belowed 0.1 μg/g. |
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