Pharmacokinetics of PEGylated recombinant human endostatin (M2ES) in rats.

AIM: M2ES is PEGylated recombinant human endostatin. In this study we investigated the pharmacokinetics, tissue distribution, and excretion of M2ES in rats. METHODS: (125)I-radiolabeled M2ES was administered to rats by intravenous bolus injection at 3 mg/kg. The pharmacokinetics, tissue distribution and excretion of M2ES were investigated using the trichloroacetic acid (TCA) precipitation method. RESULTS: The serum M2ES concentration-time curve after a single intravenous dose of 3 mg/kg in rats was fitted with a non-compartment model. The pharmacokinetic parameters were evaluated as follows: Cmax=28.3 µg·equ/mL, t1/2=71.5 h, AUC(0-∞)=174.6 µg·equ·h/mL, Cl=17.2 mL·h(-1)·kg(-1), MRT=57.6 h, and Vss=989.8 mL/kg for the total radioactivity; Cmax=30.3 µg·equ/mL, t1/2=60.1 h, AUC(0-∞)=146.2 µg·equ·h/mL, Cl=20.6 mL·h(-1)·kg(-1), MRT=47.4 h, and Vss=974.6 mL/kg for the TCA precipitate radioactivity. M2ES was rapidly and widely distributed in various tissues and showed substantial deposition in kidney, adrenal gland, lung, spleen, bladder and liver. The radioactivity recovered in the urine and feces by 432 h post-dose was 71.3% and 8.3%, respectively. Only 0.98% of radioactivity was excreted in the bile by 24 h post-dose. CONCLUSION: PEG modification substantially prolongs the circulation time of recombinant human endostatin and effectively improves its pharmacokinetic behavior. M2ES is extensively distributed in most tissues of rats, including kidney, adrenal gland, lung, spleen, bladder and liver. Urinary excretion was the major elimination route for M2ES.

Quantification of andrographolide sodium bisulphite in urine after intravenous injection to rats by LC-MS/MS.

A liquid chromatography-tandem mass spectrometry method for the determination of andrographolide sodium bisulphite (ASB) in rat urine was established and validated. To our knowledge, the analytical method is the first developed assay for the determination of ASB in urine samples. Dehydroandrographolide (DAG) was used as an internal standard. ASB and DAG were separated on a C(18) column and detected at negative ion mode using the mass transitions of m/z 413.2→287.2 and m/z 331.2→303.3, respectively. Good linearity was obtained over the range of 50-5000 ng/mL and the correlation coefficient was better than 0.99. The intra- and inter-day accuracy at all levels fell in the ranges of 85.8-101.4% and 87.9-97.5%, and the intra- and inter-day precision (RSD) were in the ranges of 4.3-11.2% and 8.4-13.3%, respectively. The recovery ranged from 96.1% to 98.3% and the matrix effects from 96.2% to 98.1%. Good stability was found under tested conditions. The method was successfully applied to a urinary excretion study of ASB in rats following intravenous administration of 80 mg/kg ASB.

Quantification of a novel natural antioxidant (UP302) in rat plasma using ultra-high performance liquid chromatography-tandem mass spectrometry.

UP302 is a novel natural antioxidant isolated from Dianella ensifolia (Liliaceae). In the investigation, a specific and sensitive ultra-high performance liquid chromatography-tandem mass spectrometry for quantitative determination of UP302 in rat plasma was developed and validated. UP302 and the internal standard daidzein were extracted from 100 µL aliquots of rat plasma using methanol. Detection of UP302 and IS was done by tandem mass spectrometry, operating in negative ion and selected reaction monitoring acquisition mode. The precursor-product ion transitions monitored for UP302 and daidzein were m/z 301.1→135.2 and 252.9→132.0, respectively. The linearity of the method was observed within the concentration range of 5-2000 ng/mL. Intra- and inter-day assay variations were less than 15%, and the accuracy values were between 99.2% and 107.3%. The method was successfully applied to stability investigation of UP302 incubated in rat plasma at 37°C and measurement of UP302 in plasma after intravenous administration of UP302 to rats at a single dose of 5 mg/kg. Incubation stability revealed that within first one hour, UP302 was rapidly declined approximately 35% and remained stable after 4 h. Pharmacokinetic values of half-life, volume of distribution, systemic clearance and mean residence time were 0.87 ± 0.58 h, 6.90 ± 3.35 L/kg, 5.89 ± 1.21 L/h kg and 0.34 ± 0.13 h, respectively.