| PS916 is a new form of sulfated amino polysaccharide that is derived from marine chitin and by ways of molecular modifications. It is characterized by 1, 4-linkedβ-D-glucosamine with an average of 1.0 sulfate and 0.5 carboxylmethyl groups per unit monosaccharide. The average molecular weight of PS916 is 7000 Da and the distribution width of molecular weight is less than 1.5. Systematic pharmacodynamic research shows that PS916 has good antiatherosclerotic activity and was authorized to enter clinical trial in China. This paper was designed to evaluate the pharmacokinetics features of PS916 in rats to provid scientific data for the new drug development and clinic use.1. The flurocescent labeling of PS916PS916, similar to other polysaccharides such as glucosan, possesses few chromophoric or fluorophoric structurally, so derect detection is impossible with violet-visible (UV-Vis) or flurocescence method, Mass spectra method is unsuitable to quantification analysis of polysaccharides either. Fluorescein-isothiocyanate (FITC) is a fluroscent labeling regent usually used to label protein, so we chose it to label PS916 because just like protein there is amino group in its structure. UV-Vis and flurocescence spectroscopy demonstrated the labeling of FITC to PS916. The maxium excition wavelength of labeled PS916 is 480nm, and the maxium emission wavelength is 515nm. Furthermore, labeled PS916 was determined spectrophotometrically by visible absorption at 490nm with reference to FITC, the content of FITC in labeled PS916 was 0.71% (w/w). The molecular weight of labeled PS916 was examined by high performance gel permeation chromatography (HPGPC). The average molecular weight and the distribution width of molecular weight of labeled PS916 were not signifficent different from that of unlabeled PS916.2. The stability of PS916 in vitro and in vivoThe stability of PS916 in vitro and in vivo was investigated using HPGPC method with fluorescesent labeled PS916. After 1, 20h incubation in phosphate buffer, rat plasma and rat urine at 37℃, the molecular weight and the width of molecular weight distribution were not changed, that showed PS916 was stable in vitro. After oral administration of PS916 to rats, PS916 was in its original form in rat plasma and rat feces, meanwhile after an intravenous administration of PS916 to rats, PS916 was also excreted in its original form in rat urine, that demonstrated PS916 metabolized in its original form.3. The establishment of analytical method of PS916 in biological matrixA rapid, sensitive fluroescence method was developed to determine PS916 in biological matrix. The linear calibration curve was obtained in the range of 0.2-20μg/mL in rat plasma. The lower limit of quantitation (LLOQ) was 0.2μg/mL. The inter-day CV% at 0.2, 2.0 and 20μg/mL of PS916 was 6.35%, 3.81% and 1.68%, respecttively. The intra-day CV% at the above concentrations was 8.42%, 4.38% and 2.14%, respectively. One-way analysis of variance (ANOVA) was carried out with grouping variable"day"to assess precision at 95% level. The result was non-significant when data for each day was compared with other days and within the same day. The calibration curves were also linear in other biological sample such as tiusse, urine and feces, range with correlation coefficient all above 0.99. The established method is suitable for PS916 pharmacokinetics studies.4. The pharmacokinetics study of PS916Individual plasma-concentration data were analyzed by non-compartmental in this paper.After intravenous and oral administration of PS916 to rats, the proportionality between dosage and Cmax or AUC was calculated,A good correlation was found between the dosage and AUC and Cmax, PS916 exhibited dose-proportional pharmacokinetics with linear kinetic character.Following oral administration, the average Tmax of three dosages was 3.28±0.58 h, that means the absorption of PS916 was slowly. After intravenous and oral administration, the average t1/2 were 7.84±0.12h and 8.74±1.01h,respectively, PS916 had a long terminal half-life.The absolute oral bioavailability of PS916 was 9.06%,which was calculated by compared the AUC0-∞of oral administration to the AUC0-∞of intravenous administration at the dose of 25mg/kg. The bioavailability of PS916 was low.After multiple dosage of PS916 at 50mg/kg, the plasma concentration–time profile was basically the same as that of signal dosage, t1/2 and AUC0-∞were non-significant between the first and the last dosage, that mean PS916 was not accumulated in rats. PS916 was widely distributed to tissues of most organs in rats 1h after oral administration of PS916, such as stomach, intestine, liver, kidneys, lung and heart. The concentration in stomach and intestine was the most highest in all tissues, the concentration in lung and liver was higher than other tissues. The concentration in stomach and intestine degraded rapidly, and increased rapidly in kidney 6h after oral administration of PS916, that show PS916 was excreted mainly by kidney after absorption. For all tissues, PS916 concentrations had significantly decreased at the time point of 24 h after oral administration. PS916 was also be detected in brain, that mean PS916 could also across blood-brain barrier.PS916 was widely distributed to tissues of most organs in rats 1h after intravenous administration of PS916, such as liver, kidneys, lung, heart and intestine. The concentration in kidney, liver and plasma was higher, the most highest in kidney, that show PS916 was excreted mainly by kidney. The concentration in most tissues such as liver, kidney, lung, heart, spleen and intestine was higher than that of plasma, that mean PS916 was widely distributed to tissues. PS916 was also be detected in brain, that mean PS916 could also across blood-brain barrier. PS916 was mainly excreted in its original form from feces and urine after oral administration. Cumulative amounts percentage of PS916 in feces at 72 h after an oral dose was 78.974±5.498%. Cumulative amounts percentage of PS916 in urine at 72 h after an oral dose was 1.288±0.958%. Drug which was excreted totally in urine and feces in 72 h after an oral administration of PS916 was equal to 80.26% of given dose. PS916 was mainly excreted from feces after oral administration.PS916 was mainly excreted in its original form from feces and urine after oral administration. Cumulative amounts percentage of PS916 in urine at 72 h after an oral dose was 54.388±11.832%. Cumulative amounts percentage of PS916 in feces at 72 h after an oral dose was 6.286±1.938%%. Drug which was excreted totally in urine and feces in 72 h after an oral administration of PS916 was equal to 60.67% of given dose. PS916 was mainly excreted from urine after oral administration.
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