In the present study, a simple, rapid, and sensitive liquid chromatography-tandem mass spectrometric method for the determination of axitinib in nude mouse plasma was developed, validated, and applied to a pharmacokinetic study. Plasma samples were pre-treated by protein precipitation with acetonitrile spiked with erlotinib as an internal standard. The chromatographic separation was accomplished by using a reversed phase C18 column （50 mm×2 mm, 5 μm） with a simple mobile phase system composed of methanol and water （60：40, v/v） at an isocratic flow rate of 0.4 mL/min. The analyte was detected by a triple-quadrupole tandem mass spectrometer via electrospray ionization and multiple reaction monitoring was employed to select both axitinib and erlotinib in the positive ion mode. The calibration curves were linear （r〉0.99） ranging from 1 to 1000 ng/mL, and the lowest level of this range was the lower limit of quantification. The intra- and inter-day precision were 7.7%-12.0%, and the accuracies ranged from 88.6% to 110.4%. This method was successfully applied to a preclinical pharmacokinetic study on female nu/nu nude mice administrated with a single oral dose of axitinib at 120 mg/kg, and the pharmacokinetics was characterized by a one-compartment model with first-order absorption.
In the current study, we established and validated a simple and sensitive liquid chromatography-tandem mass spectrometric method for the determination of 21-hydroxy deflazacort in nude mice plasma, and such a method was applied to a pharmacokinetic study. Using betamethasone as the internal standard, the plasma samples were pre-treated by precipitation with acetonitrile and then analyzed on a reversed-phase C18 column （50 mm×2 mm, 5 μm） with a mobile phase consisting of acetonitrile and 4.0 mM ammonium formate （pH was adjusted to 3.5 with formic acid （40：60, v/v））. The analyte was detected by a triple quadrupole tandem mass spectrometer using electrospray, and multiple reaction monitoring was employed to select 21-hydroxy deflazacort at m/z 400.2/124.0 and betamethasone at m/z 393.3/147.0 in the positive ion mode. The calibration curves were linear （r〉0.99） over the range of 0.5~,00 ng/mL. The intra- and inter-day precisions and accuracies were 4.5%-10.1% and -1.7%-10.7% respectively. This method was successfully applied to a preclinical administered with a single oral dose of 4 mg/kg deflazacort, and its pharmacokinetic study of deflazacort on female nude mice pharmacokinetics was characterized by a two-compartment model with first-order absorption.
Sulfotransferases（SULTs） are one of the most important phase II drug-metabolizing enzymes. Among them, aryl sulfotransferases（SULT1A1） and estrogen sulfotransferase（EST, SULT1E1） belong to the rSULT1 family that catalyzes sulfation of phenolic compounds. Dopamine（DA） acts as a vital neurotransmitter in central nervous system（CNS） and regulates a variety of activities in periphery. In our study, we aim to detect the effects of exogenous DA and levodopa（L-DOPA） on rSULTs（rSULT1A1 and rSULT1E1） in rat liver. In order to achieve this target, varying doses of DA（0, 2, 10 and 100 mg/kg/d） and L-DOPA（0, 5, 25 and 125 mg/kg/d） were provided to male and female rats, respectively. Real-time PCR assay and western blot were used in the determination of the mRNA and protein expression of rSULTs. PNPS assay and radioactivity assay were applied to the detection of enzyme activity of rSULT1A1 and rSULT1E1, respectively. Our results showed that DA induced the expression and activity of rSULT1A1 in the liver of male and female rats and DA had little effect on rSULT1E1. However, L-DOPA caused no evident change of rSULT1A1 in both sex and had no significant effect on rSULT1E1 in female rat liver, but increased rSULT1E1 expression and activity only in male rat liver when administered at high dose. Our results suggest that DA plays different roles in the regulation of rSULT1A1 and rSULT1E1 when it is in periphery or in the CNS.
A sensitive, rapid, and simple liquid chromatography tandem mass spectrometry（LC-MS/MS） method for simultaneous determination of sunitinib and its active metabolites in plasma of BABL/c nude mice was developed and validated. Plasma samples were pre-treated by protein precipitation with pazopanib and used as an internal standard. Separation was performed on a reversed phase C18 column with a mobile phase composing of 10 m M ammonium formate p H 3.25（adjusted with formic acid） and acetonitrile（65：35, v/v） at a flow rate of 0.5 mL /min. Triple quadrupole tandem mass in multiple reaction monitoring（MRM） mode with electrospray positive ionization was used to monitor all the compounds. The current LC-MS/MS method was highly selective and sensitive with lowest limit of quantitation（LLOQ） of 0.5 ng/mL for both analytes and reliable intra- and inter-day precision and accuracy validated by relative error（RE%） and relative standard deviation（RSD%）. Linearity of calibration curve was excellent（r0.99） within a concentration range of 0.5–1000 ng/mL. This method was successfully applied to a pharmacokinetics study on BABL/c nude mice given with single dose of oral administration of sunitinib at 20 mg/kg.
