| Sodium phenylbutyrate (PB) is a differentiating agent with the molecular structure of aromatic fatty acid. PB exerts broad effects on tumor cytostasis and differentiation, altering gene expression for tumor growth, invasion, angiogenesis, and immunogenicity. But its pharmacokinetics hasn't studied deeply. In this paper, we have developed an RP-HPLC method for separation and determination of PB in rats' serum. At the same time, we study the pharmacokinetics of PB after different administration of PB.Material and MethodsChromatographic Conditions Chromatographic column: C|g-ODS(5u )(25cmX 4.6mm); mobile phase: methanol-50mM sodium acetate buffer (pH6.5; 36:64,v/v); flow rate: l.Oml-min"1; wavelength of UV detector: 218nm; sensitivity: 0.2AUFS; paper rate: 0.1 cm-min"'; injection volume: 20 M 1.Sample Preparation and Extraction Carotid blood samples 1.0ml were collected in 10ml centrifugal tubes. Two hours later, blood was centrifuged at 2000 rpm for 10 minutes. Serum samples were then stored in 1.0 ml Eppendorf tube at -10"C until assayed.Two hundred u 1 of thawed serum were piped into a 1.0 ml Eppendorf tube. Protein precipitation was carried out by adding lOOu 1 of a 10% (v/v) solution ofperchloric acid. The tube was vortexed for 20 seconds and then centrifuged at 5000 rpm for 10 minutes. One hundred and fifty u 1 of supernatant were transfeTed to a new 1.0 ml Eppendorf tube and 25 u I of 20% KHCO3 (w/v) were added to neutralize the solution. This was centrifuged at 5000 rpm for 10 minutes and 20 u 1 of supernatant was injected onto the ODS column.Animals and Administration Routes Female Sprague Dawley rats weighting about 230g received PB from follow administration routes: (1) a single iv injection of PB in dose of 125, 250, 400 mg-kg"1, respectively; (2) multiple iv administration of PB in a total dose of 250 mg-kg"1; (3) ig administration of PB in dose of 2.0g-kg"'. Pharmacokinetic Parameters Count and Statistics Methods Pharmacokinetic models of single and multiple iv injection we' determined by Akaike's Information Criterion (AIC) and pharmacokinetic parameters were estimated using according formulas. The parameters of ig administration were counted by 3P87 pharmacokinetic software .All results were expressed as the mean盨d. Difference between groups for Tl/2, AUC, CL, K, etc. were determined by analysis of variance (ANOVA). Statistical significance was claimed when P<0.05.Results1. The assay was good separation for PB and endogenous substances of serum, and good linear between concentrations of 20 to 800 y g-inl"'. The regression equation of the calibration curve based on the PB serum concentration versus the peak high was y=46.45+4.69C (r=0.9998). The average recoveries were 97.75 ?6.69%. The within-day and the between-day assay relative standard deviation were 3.13-7.02 % and 2.66~3.89 %, respectively. The assay yielded a lower limit of quantitation of 8.0 n g-mr'and the retention time of PB was 14.15 minutes.20022. The concentration-time profile of PB in rats after iv in dose of 125, 250, 400mg-kg"' were shown to fit one-compartment nonlinear pharmacokinetic model, kra were 143.8 + 67.88 u g-ml'1, 278.44 + 121.2 n g-ml"1 and 826.86 ?107.52 u g-ml'1, respectively. At multiple iv injections of PB in a total dose of 250 mg-kg"',the time of plasma concentration of PB above O.SmM was longer than which of a single iv injection of PB in the same total dose for about 30min (P<0.05). The concentration-time curve of PB in rats fitted one-compartment after oral administration in dose of 2.0g-kg"'. The elimination rate constant (Ke) was 0.76?.04 h"1, Tpeak was 0.68 + 0.05 h, Cmax was 762.28 + 106.24 u g-ml"1, AUC was 1672.68+ 199.61 u g-h-ml"',the absorption rate constant (Ka) was 2.56+0.31 h"1. The plasma concentration of PB in portal vein versus that in carotid was 1.61 +0.29(P<0.05), which suggested there was the first pass effect of liver after ig PB in SD rats.
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