Effect of CYP2C9 Genetic Polymorphism in a Chinese Population on the Metabolism of Mestranol in vitro.

BACKGROUND: Mestranol is a widely used estrogen, which is converted into its active metabolite ethinyl estradiol by cytochrome P450 (CYP) 2C9. To comprehensively examine the enzymatic activity of reported CYP2C9 variants in Chinese individuals in response to mestranol, wild-type CYP2C9*1 and 35 allelic variants were highly expressed in Sf21 insect cell microsomes and used for the detection of their enzymatic values in vitro. These results showed that the majority of tested variants exhibited decreased clearance values compared to wild type, except for CYP2C9*40 and *36. METHOD: Insect microsomes expressing the 36 CYP2C9 variants were incubated with 0.25-8 µmol/l mestranol for 30 min at 37°C. Then, the production of the metabolite of mestranol, ethinyl estradiol, was analyzed using high-performance liquid chromatography. RESULTS: Most CYP-catalyzed reactions were sufficiently described by classical Michaelis-Menten kinetic parameters (e.g., Km and Vmax), while 9 variants exhibited atypical or non-Michaelis-Menten kinetic values, which were largely due to the self-inhibitory effect in response to mestranol. CONCLUSION: This is the first report of these rare alleles for mestranol metabolism, which provides fundamental data for further clinical studies on CYP2C9 alleles for mestranol metabolism.

Determination and pharmacokinetic study of pirfenidone in rat plasma by UPLC-MS/MS.

A rapid, sensitive and selective ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) was developed and validated for the determination and pharmacokinetic investigation of pirfenidone in rat plasma. Sample preparation was accomplished through a simple one-step deproteinization procedure with 0.2 mL of acetonitrile to a 0.1 mL plasma sample. Plasma samples were separated by UPLC on an Acquity UPLC BEH C18 column using a mobile phase consisting of acetonitrile-0.1% formic acid in water with gradient elution. The total run time was 3.0 min and the elution of pirfenidone was at 1.39 min. The detection was performed on a triple quadrupole tandem mass spectrometer in the multiple reaction-monitoring (MRM) mode using the respective transitions m/z 186.2→92.1 for pirfenidone and m/z 237.1→194.2 for carbamazepine (IS), respectively. The calibration curve was linear over the range of 5-2000 ng/mL with a lower limit of quantitation (LLOQ) of 5 ng/mL. Mean recovery of pirfenidone in plasma was in the range of 80.4-84.3%. Intra-day and inter-day precision were both <12.1%. This method was successfully applied in pharmacokinetic study after oral administration of 10.0mg/kg pirfenidone in rats.

The effect of apigenin on pharmacokinetics of imatinib and its metabolite N-desmethyl imatinib in rats.

The purpose of this study was to determine the effect of apigenin on the pharmacokinetics of imatinib and N-desmethyl imatinib in rats. Healthy male SD rats were randomly divided into four groups: A group (the control group), B group (the long-term administration of 165 mg/kg apigenin for 15 days), C group (a single dose of 165 mg/kg apigenin), and D group (a single dose of 252 mg/kg apigenin). The serum concentrations of imatinib and N-desmethyl imatinib were measured by HPLC, and pharmacokinetic parameters were calculated using DAS 3.0 software. The parameters of AUC(0-t), AUC(0-∞), Tmax, V(z)/F, and CL(z)/F for imatinib in group B were different from those in group A (P < 0.05). Besides, MRT(0-t) and MRT(0-∞) in groups C and D differed distinctly from those in group A as well. The parameters of AUC(0-t) and Cmax for N-desmethyl imatinib in group C were significantly lower than those in group A (P < 0.05); however, compared with groups B and D, the magnitude of effect was modest. Those results indicated that apigenin in the short-term study inhibited the metabolism of imatinib and its metabolite N-desmethyl imatinib, while in the long-term study the metabolism could be accelerated.

The effect of glycyrrhetinic acid on pharmacokinetics of cortisone and its metabolite cortisol in rats.

The purpose of this paper is to study pharmacokinetics of cortisone (E) and its metabolite cortisol (F) in rats after administration of glycyrrhetinic acid (GA) and cortisone. Healthy male SD rats were randomized to be given 20 mg/kg E or E combined with 10 mg/kg GA. Blood samples were collected at 5, 10, 20, 40, 60, 90, 120, 150, 180, and 240 min after administration. The serum concentrations of E and F were determined by HLPC and pharmacokinetic parameters were calculated using DASver2.0 software. The parameters of AUC((0-t)), AUC((0-∞)), and C(max) for E in the group of E + GA were significantly higher than those in the group of E (P < 0.01); the half-time (t(1/2ß)) was extended compared to E (P < 0.05) and CL/F was dropped obviously (P < 0.01). The rise in AUC((0-t)), AUC((0-∞)), and C(max) for cortisol in the group of E + GA was significantly compared to the group of E (P < 0.01). CL/F was lower than E (P < 0.01) and the half-time (t(1/2ß)) was slightly extended. In this study, we find that GA restrains the metabolism of E and F and thus increases AUC, t(1/2ß), and C(max) of E and F, which may be related to its inhibition effect on 11ß-hydroxysteroid dehydrogenase (11ß-HSD).

[Toxicokinetics of paraquat in rabbits].

OBJECTIVE: to develop a high performance liquid chromatography method (HPLC) for the determination of paraquat in rabbit plasma and study its toxicokinetics in rabbits. METHODS: twelve rabbits were randomly divided into 2 groups with giving oral and intravenous administration of paraquat at a single dose of 60 mg/kg and 6 mg/kg respectively. The plasma paraquat concentrations were determined by HPLC and calculated by DAS pharmacokinetics program. RESULTS: the linear range of paraquat in plasma was 0.05 ∼ 50.00 mg/L (r = 0.9998). The relative recoveries of the assay were 99.41% ∼ 102.32%. The absolute recoveries of the assay were 83.72% ∼ 90.48%. Both the intra-day and inter-day validations were less than 10%. For oral administration, the toxicokinetics parameters of paraquat were as follows: Cmax (14.46 ± 2.35) mg/L, Tmax (1.63 ± 0.31) h, AUC(0-t) (177.61 ± 14.62) mg × h/L, AUC(0-∞) (182.24 ± 14.54) mg × h/L, While for intravenous administration, the toxicokinetics parameters of paraquat: Cmax (35.13 ± 5.53) mg/L, Tmax 0.05 h, AUC(0-t) (121.74 ± 12.30) mg × h/L, AUC(0-∞) (125.12 ± 12.17) mg × h/L, The difference of these parameters between the two groups had statistical significance (P < 0.05). The oral bioavailability was (14.66 ± 1.55)%. CONCLUSION: the oral bioavailability of paraquat is relatively low. The biological half life of paraquat is relatively long and there is no significant difference between oral administration and intravenous on biological half life. This method is simple, sensitive and accurate. It can be used for the investigation of paraquat in rabbits.

[Effects of forest cutting on greenhouse gas emissions from Larix gmelini-Sphagnum swamps in Lesser Xing' an Mountains of Heilongjiang, China].

By using static chamber and gas chromatography methods, this paper studied the effects of clear cutting and selective cutting on the CO2, CH4, and N2O emissions from Larix gmelini-Sphagnum swamp in Lesser Xing' an Mountains. Dramatic changes in the seasonal dynamics of CH4 and N2O emissions were detected in different treatment sites. Control site absorbed CH4 in summer and emitted CH4 in autumn, and absorbed N2O in both summer and autumn; selective cutting site emitted CH4 and N2O mainly in summer; and clear cutting site emitted CH4 in summer and autumn, and absorbed N2O in summer but emitted it in autumn. Cutting pattern had less effects on the seasonal dynamics of CO2 emission. Both on the clear cutting site and on the selective cutting site, the CO2 emission was in order of summer > spring > autumn. Forest cutting altered the source and sink functions of the sites. Control site functioned as a source of CO2 and a weak sink of CH4 or N2O, while forest cutting sites had a decrease of CO2 emission by 25%, and became a weak source of N2O and a weak or strong source of CH4. Compared with that of control site, the Global Warming Potential (GWP) of selective cutting site and clear cutting site was reduced by 24.5% and increased by 3.2%, respectively.