Mechanism for drug absorption from rat-liver surface membrane: effect of dose and transport inhibitors on the pharmacokinetics of phenol red

We examined the effect of dose and transport inhibitors on the pharmacokinetics of phenol red as a model drug after application to rat liver surface in-vivo, employing a cylindrical glass cell (i.d. 9 mm, area 0.64 cm2), to elucidate the mechanism for drug absorption from liver surface membrane. Absorption ratios of phenol red in 6 h were determined to be 91.1, 91.8 and 89.9 % at a dose of 0.3, 1 and 3 mg, respectively. Also, the AUC value for plasma concentration profile of phenol red was proportional to the dose. It is thus suggested that absorption process of phenol red from rat liver surface does not approach saturability. Time course of remaining amount of phenol red in glass cell obeyed the first-order kinetics at a dose of 0.3 mg, and its rate constant Ka was calculated to be 0.0069 min-1. Moreover, no significant difference was seen in Ka value within the dose range of 0.3 - 3 mg, which was estimated by curve fitting of the plasma concentration profile of phenol red after application to rat liver surface in the two-compartment model with first-order absorption. 2,4-Dinitrophenol (0.3 mg) and probenecid (0.5 and 1 mg), inhibitors of metabolic energy and anion transport respectively, had no significant effect on the pharmacokinetics of phenol red after application to rat liver surface. These data demonstrate that specific transport mechanism such as active transport is not involved in phenol red absorption from rat liver surface membrane.without figuresグラフな

Gene therapy for gastric diseases.

Gene therapy for gastric cancer and gastric ulcer is a rationalized strategy since various genes correlate with these diseases. Since gene expressions in non-target tissues/cells cause side effects, a selective gene delivery system targeted to the stomach and/or cancer must be developed. The route of vector transfer (direct injection, systemic, intraperitoneal, gastric serosal surface and oral administration) is an important issue which can determine efficacy and safety. Strategies for cancer gene therapy can be categorized as suicide gene therapy, growth inhibition and apoptosis induction, immunotherapy, anti-angiogenesis, and others. Combination of the target gene with other genes and/or strategies such as chemotherapy and virotherapy is promising. Candidates for treatment of gastric ulcer are vascular endothelial growth factor, angiopoietin-1, serum response factor, and cationic host defense peptide cathelicidin. In this review, we discuss stomach- and cancer-targeted gene transfer methods and summarize gene therapy trials for gastric cancer and gastric ulcer

Pharmacokinetic analysis of in vivo metabolism of amino acid or dipeptide conjugates of salicylic acid in rabbit intestinal microorganisms

We analyzed the pharmacokinetics of salicylic acid (SA)-amino acid (alanine, glutamic acid, methionine, and tyrosine) or SA-dipeptide (glycylglycine) conjugates in rabbits, by using a model that takes into account the metabolism of prodrug to SA by intestinal microorganisms and, also, by model-independent analysis. The blood concentration profiles of these prodrugs and released SA following intracecal and oral administration to rabbits were obtained previously (Nakamura et al., J. Pharm. Pharmacol., 44, 295-299, 1992; Chem. Pharm. Bull., 40, 2164-2168, 1992; Int. J. Pharm., 87, 59-66, 1992; J. Pharm. Pharmacol., 44, 713-716, 1992). First, the overall in vivo behavior was evaluated by statistical moment analysis. Next, the blood concentration profiles of prodrug and SA following intracecal and oral administration were simultaneously fitted to the above model. In general, good agreement was observed between fitted lines and experimental data for every prodrug, suggesting the validity of this model. The obtained parameters characterized the difference in the rate of metabolism and absorption among the prodrugs. Lower absorbability and enhanced hydrolysis rate of the prodrug lead to prolonged blood concentration of SA.without figuresグラフな

Absorption of organic anions as model drugs following application to rat liver surface in-vivo

Absorption of organic anions (phenol red, bromphenol blue and bromosulphonphthalein) has been studied after their application to rat liver surface in-vivo, employing a cylindrical glass cell (i.d. 9 mm, area 0.64 cm2). Every drug appeared gradually in the blood with the peak level at about 1 h, after which its concentration declined slowly. Absorbed model drug was efficiently excreted into the bile. These observations appear to indicate the possibility of drug absorption from liver surface membrane. Absorption ratios of model drugs were estimated to be more than 59 % in 6 h. As to phenol red, its biliary recovery and metabolism ratio did not change as compared with that of i.v. administration.without figuresグラフな

Effect of albumin on the absorption of phenol red, bromphenol blue and bromosulphonphthalein as model drugs from the liver surface membrane in rats,

The effect of bovine serum albumin (BSA) on drug absorption from the liver surface in rats was examined by using three organic anions (phenol red, bromphenol blue and bromosulphonphthalein) as model drugs which have a high affinity for albumin. The binding ratio of the model drugs (3 mg/ml in phosphate buffer) to BSA varied widely at a BSA concentration of 0.1--10% (w/v). The model drugs (3 mg/ml x 0.1 ml) with or without BSA were applied to the rat liver surface in vivo employing a cylindrical glass cell (i.d. 9 mm, area 0.64 cm2). The absorption ratios of the model drugs from the rat liver surface at 6h, calculated from the amount recovered from the glass cell, decreased with an increase in BSA concentration. A similar trend was observed with biliary recovery of the model drugs. A marked reduction in the absorption ratio was seen with bromosulphonphthalein, which has the highest binding activity to BSA among the three organic anions. Accordingly, protein binding appears to be a significant factor with respect to the drug absorption from the liver surface.グラフなしwithout graph

Absorption of phenol red and bromphenol blue as model drugs from the peritoneal cavity around the liver surface in rats

The effect of the injection site on the pharmacokinetics of phenol red and bromphenol blue as model drugs after intraperitoneal (i.p.) administration into rats was examined. Their absorption rate from the peritoneal cavity was faster after i.p. administration to the liver surface (LS) than that after i.p. administration to the distal small intestine (SI), as shown by the increase in maximum concentration and decrease in mean residence time in plasma. A similar tendency was observed in the biliary excretion pattern. The enhanced absorption rate was supported by the significantly smaller amount of both drugs remaining in the peritoneal cavity at 15 min after LS administration than that after SI administration. The liver concentration of the model drugs at 15 min after LS administration was 1.5 - 2.0 times higher than that after SI administration. Accordingly, LS administration was shown to be effective with good absorbability and efficient drug delivery to the liver.without figuresグラフな

Flavonoids Enhance Lipofection Efficiency and Ameliorate Cytotoxicity in Colon26 and HepG2 Cells via Oxidative Stress Regulation

The generation of reactive oxygen species (ROS) can affect cationic liposome-mediated transfection. In this study, we focused on a specific class of antioxidants, flavonoids, to investigate the transfection efficiency using cationic liposome/plasmid DNA complexes (lipoplexes) in 2D and 3D cultures of Colon26 and HepG2 cells, respectively. All tested flavonoids enhanced the transfection efficiency in 2D Colon26 and HepG2 cells. Among the tested flavonoids, 25 µM quercetin showed the highest promotion effect of 8.4- and 7.6-folds in 2D Colon26 and HepG2 cells, respectively. Transfection was also performed in 3D cultures of Colon26 and HepG2 cells using lipoplexes with quercetin. Quercetin (12.5 µM) showed the highest transfection efficiency at all transfection timings in 3D Colon26 and HepG2 cells with increased cell viability. Flow cytometry revealed that quercetin treatment reduced the population of gene expression-negative cells with high ROS levels and increased the number of gene expression-positive cells with low ROS levels in HepG2 cells. Information from this study can be valuable to develop strategies to promote transfection efficiency and attenuate cytotoxicity using lipoplexes

Absorption characteristics of compounds with different molecular weights after application to the unilateral kidney surface in rats

The aim of the present study is to clarify the absorption mechanism of a drug from the kidney surface membrane in rats. We studied the absorption characteristics of phenolsulfonphthalein (PSP) and other compounds with different molecular weights after their application to the rat kidney surface in vivo, employing a cylindrical diffusion cell (i.d. 6 mm, area 0.28 cm2). The time course of free PSP amounts remaining in the diffusion cell obeyed first-order kinetics at a dose of 1 mg, and its rate constant ka was calculated to be 0.0137 min?1. Absorption ratios of PSP in 4 h were calculated (from the amount recovered from the diffusion cell) to be 91.4, 96.4 and 97.7% at doses of 0.5, 1 and 1.5 mg, respectively. The area under the curve for the plasma concentration profile of free PSP was proportional to the application dose. It is thus suggested that the absorption process of PSP from the rat kidney surface does not approach saturation at a dose of 1.5 mg. Also, no significant difference was seen in the ka values within the dose range of 0.5?1.5 mg, which were estimated by curve-fitting the plasma concentration profiles of free PSP in a two-compartment model with first-order absorption. Furthermore, we examined the importance of molecular weight on the absorption from the kidney surface using fluorescein isothiocyanate-dextrans (FDs) with molecular weights of 4400 (FD-4), 11,000 (FD-10), 40,500 (FD-40) or 69,000 (FD-70), including the organic anions bromphenol blue and bromosulfonphthalein. The absorption ratios of FDs from the rat kidney surface in 6 h decreased with an increase in the molecular weight (76.1% for FD-4, 54.4% for FD-10, 11.5% for FD-40 and 3.9% for FD-70). A linear relationship was observed between ka and the reciprocal value of z the square root of the molecular weight of these compounds. The limit of absorption from the rat kidney surface was extrapolated to be at a molecular weight of approximately 130,000

Effect of application volume and area on the absorption of phenol red as a model drug from the liver surface in rats

We examined the importance of application volume and area in the absorption of phenol red as a model drug from the rat liver surface, for pharmaceutical formulation concerning administration form. When 1 mg of phenol red was applied to the rat liver surface in-vivo using a cylindrical glass cell (i.d. 9 mm) in three volumes (0.1, 0.2 or 0.334 mL), the shape of the plasma concentration pattern differed greatly, particularly the maximum concentration. These patterns were well fitted by a two-compartment model with first-order absorption, and the obtained absorption rate constant Ka decreased inversely according to the application volume. The absorption ratio and biliary recovery of phenol red at 6 h was increased with glass cell area (i.d. 6, 9 or 14 mm; area 0.28, 0.64 or 1.54 cm2). Furthermore, the permeability coefficient Papp derived from Ka did not depend on application area, indicating no difference in absorption characteristics of liver surface. This also implies transport of a drug by a passive diffusion from the liver surface. After intraperitoneal administration to the rat liver surface for clinical application, increase in application volume resulted in the delayed disappearance of phenol red from plasma. However, the difference was not as marked as that using a glass cell. The assumption that the effective area relating to the absorption changed with the application volume enabled us to estimate Papp. Consequently, we speculate absorbability can be estimated precisely by considering application volume and area