No abstract

The study aimed to study the influence of different reaction temperatures on the carp (Cyprinus carpio) hepatic CYPs activity. Six groups of carp hepatic microsomes were incubated with probe drug (chorzoxazone) at 5, 10, 15, 20, 25 and 30°C separately. According to the principle of enzyme kinetics theory, the Michaelis constant (K (m)) value and maximum reaction velocity (V (max)) of CYPs (with CZX as probe) were obtained. The CYPs activity at different reaction temperatures was compared. In results, the K (m) values were separately 44.62, 31.35, 26.59, 21.75, 16.39, 29.69 μM, and the V (max) were separately 0.231, 0.234, 0.265, 0.294, 0.315, 0.239 nmol min(-1)mg(-1) at 5, 10, 15, 20, 25, 30°C. Results indicated that the enzyme CYPs activity was much higher at 25°C. It was also demonstrated that reaction temperature could affect the CYPs activity significantly. Therefore, this experiment builded a theoretical basis for the variations of fish pharmacokinetic parameters at different water temperatures and contributed to further research on the influence of water temperature on fish drug metabolism.

No abstract

The pharmacokinetics and residues elimination of Minocycline(MINO) were studied in healthy carp (Cyprinus carpio，400±30 g) kept at water temperatures of 10 and 25°C. The concentrations of MINO in plasma and tissues were determined using highperformance liquid chromatography (HPLC) using an ultraviolet detector. The plasma concentrations of MINO concentration-time data were fitted using a singlecompartment model at 10 and 25°C. The absorption half-life (t1/2ka) of MINO was 2.65 h at 10C and 1.65 hat 25C, whereas the elimination half-life (t1/2ke) was 11.16 h at 10 C and 16.343.78 h at 25C; the maximum plasma concentration (Cmax) and the time-point of maximum plasma concentration (Tp) were calculated as 2.34 µg mL-1 and 7.21 h at 10C, 2.97 µg mL-1 and 3.50 h at 25C. The distribution volume (Vd/F) of MINO was estimated to be 4.09 L kg-1 at 10 °C and 2.66 L kg-1 at 25 °C; the total body clearance (CLb) of MINO were computed as 0.25 and 0.49 L/ (h•kg) at 10 and 25°C, respectively; the areas under the concentration-time curve (AUC) was 59.07 µg mL-1 h at 10°C and 30.72 µg mL-1 h at 25°C. The concentrations of MINO were detected in muscle, skin, liver and kidney. The MINO could still be detected at 5 d time-point after administration at both temperatures in all tissues. The results revealed that the depletion of MINO in carp was slower with a long half-life time, especially at lower water temperature. If fish were administered MINO orally with a single dose (10 mg/kg•bw) for several days, the withdrawal periods of MINO could be not less than 19 d at winter water temperature (10℃) and 8 d at summer water temperature (25℃).