Objective:To establish an HPLC-MS/MS method for the determination of vinblastine in rat plasma. Methods:Aceto-nitrile was used to precipitate protein in the samples after the addition of internal standard, and then the concentration was analyzed by HPLC/MS/MS. All the separations were carried out on an Ultimate C18 column (150 mm × 2. 1 mm, 5. 0 μm). The mobile phase was composed of acetonitrile and 10 mmol·L-1 ammoniumacetate (containing 0. 1% formic acid) (49 ∶51) and was pumped at a flow rate of 0. 3 ml·min-1 under 40 °C. The detection was performed with multiple reactions monitoring (MRM) using electrospray ioniza-tion (ESI). The precursor/product ion transitions were monitored at m/z 811. 4→m/z 224. 2 (positive ion mode) for vinblastine and m/z 825. 4→m/z 807. 4(positive ion mode) for internal standard vincristine. Results:Good linearity of vinblastine was obtained with-in the range of 0. 457-950 ng·ml-1(r=0. 997 1). The lower limit of quantification was 0. 457 ng·ml-1. The extraction recoveries were within the range of 89. 15%-95. 28%. The precision of intra-and inter-day was not more than 7. 95%. T1/2 of vinblastine in rats was (5. 86 ± 2. 37) h, and AUC(0-t) and AUC(0-∞) was (68. 45 ± 14. 51) and (95. 03 ± 33. 09)μg·L-1 ·h, respectively. Conclu-sion:The method is fast, sensitive and accurate, which provides research basis for the development of vinblastine and transporters re-search in medicine. The concentration of vinblastine in rats is low, and the half-life is long.

Objective:To investigate the in vitro effect of capsaicin on four major rat cytochrome P450 ( CYP) enzymes using a cocktail probe drug method. Methods:The in vitro incubation was divided into capsaicin group and the control group. Rat liver micro-somes, probe drugs, capsaicin at various concentration ( buffer solution in the control group) and cofactors were cultured altogether for 20 min. After the culture, the concentration of metabolites was determined by HPLC to assess the activities of enzymes. IC50 value of capsaicin on every isoform was calculated using Graphpad prism 5. 0. Capsaicin and hepatic microsomess were pre-incubated respec-tively for 0, 5, 10, 15, 20 and 30 min, and then the relative activity of the four isoforms at different time was calculated. Results:The activity of the rat liver microsomes enzyme CYP450 isoforms (CYP1A2, CYP2C11, CYP2E1 and CYP3A2) was all inhibited by capsaicin in vitro with IC50 value of 36. 21, 17. 19, 51. 64 and 18. 86 μmol·L-1 , respectively. Pre-incubation could not increase cap-saicin inhibitory activity against the four CYP enzymes. Conclusion:Capsaicin shows inhibition on CYP1A2, CYP2C11, CYP2E1 and CYP3A2 in rat liver microsomes in vitro without pre-incubation time-dependent property.

BACKGROUND: It is recently found that some kinds of antibiotics can aggravate the obstruction of neuromuscular junction(NM J) transmission,exacerbate myasthenia gravis (MG). Hitherto, there are few reports about the effect of antibiotics on transitive function on animal models. Along with the appearance of new antibiotics, the effects of the antibiotics on NMJ transitive function need to be further observed.OBJECTIVE: To investigate the effect of aminoglycoside antibiotics, fluoroquinolone antibiotics and cephalosporin antibiotics on the transitive function of NMJ in MG, and to provide an experimental basis for using those antibiotics securely in clinic and for selecting those antibiotics to treat MG properly.DESIGN: Randomized controlled study based on experimental animals.SETTING: Department of nosocomial infection, neurology and pharmacy in a university hospital.MATERIALS: The experiment was conducted at the Neurological Institute of Tongji Medical College, Huazhong University of Science and Technology from March 2002 to January 2003. Totally 150 healthy female C57BL/6mice, 6 - 8 weeks old, weighting 18 - 20 g, were divided randomly into 4groups: normal group( n = 10), MG group( n = 10), saline group( n = 10)and antibiotics group( n = 120) . Mice in antibiotics group were divided randomly again into gentamicin group, etimicin group, ciprofloxacin group,fleroxacin group, cefuroxime group and cephradine group, with 20 mice in each group.INTERVENTIONS: C57BL/6 mice were immunized with the acetylcholine receptor(AChR) protein in complete Fruend' s adjuvant(CFA) to establish experimental autoimmune myasthenia gravis(EAMG) . Mice in saline group were injected normal saline and mice in antibiotics group were injected antibiotics(10 mg/kg), lasted 14 days. Mice in MG group were without any treatments. On the 7th day after the last immunization and the 14th day after the antibiotics treatments, MG scores was evaluated, repetitive nerve stimulation(RNS) and the levels of acetylcholine receptor antibody(AChRab)were tested at the same time.RESULTS; The mean symptom scores on the 14th day after the antibiotics treatment with gentamicin, etimicin, ciprofloxacin and fleroxacin were higher than that in MG group, and there was no significant difference in the mean symptom scores among cefuroxime group, cephradine group and MG group. The decrement percent of RNS in gentamicin group [ (21.22 ± 4.63)% ], etimicin group[ (19.08 ±4. 25)% ], ciprofloxacin group[ (22.25 ±4.95)% ] and fleroxacin group[ (21.71 ±4.99)% ] were higher than that in MG group[(15.75 ±2.22)% ], but no difference was found in the attenuation rate among cefuroxime group[(15.25 ±2. 87)% ],cephradine group[ ( 15.25 ± 3.30)% ] and MG group. The levels of AChRab in gentamicin, etimicin, ciprofloxacin and fleroxacin groups were also higher than that in MG group, but no difference was found among cefuroxime group, cephradine group and MG group.CONCLUSOIN: Aminoglycoside and fluoroquinolone antibiotics can aggravate the obstruction of NMJ transmission, and cephalosporin antibiotics have no obvious effect on the obstruction of NMJ transmission function in MG.