摘要:

AbstractThe effect of enterocyte-like differentiation on the transferrin receptor (TfR) polarity in filter-grown Caco-2 cells was studied. The ratio of apical to basolateral TfRs which was found to be approximately 1:1 on the first day after the cells had reached confluence, changed to 1:40 eight days after reaching confluence. The transepithelial electrical resistance (TEER), transport of horseradish peroxidase (HRP) across the monolayer, and total cellular TfR number remained constant over this period. However, the activity of brush border membrane-associated alkaline phosphatase, an established marker for enterocyte differentiation, increased over this 8-day period concurrent with a decrease in apical TfR number. These results suggest that enterocyte-like differentiation rather than tight junction formation is most likely responsible for the polarized distribution of TfRs in Caco-2 cells. The effects of the fungal metabolite brefeldin A (BFA) on TfR distribution and TfR-mediated transcytosis in Caco-2 cells were also studied. BFA caused a marked decrease in the number of basolateral TfRs along with a slight increase in the number of apical TfR. BFA enhanced the TfR-mediated transcytosis of both125I-Tf and the horseradish peroxidase-Tf conjugate across Caco-2 cells in both apical-to-basolateral and basolateral-to-apical directions. These findings imply a potential application of BFA as an enhancer for TfR-mediated delivery of protein drugs across the intestinal epithelium.

ISSN:1061-186X    

DOI:10.3109/10611869409015897

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractPrevious work has shown that proteins can be nondestructively delivered into the cytoplasm of folate receptor-bearing cells if the proteins are conjugated to folic acid prior to addition to cells. In view of other reports suggesting the membrane receptor for folic acid is vastly overexpressed on tumor cells, we decided to explore whether malignant cells might be selectively targeted in a co-culture with nontransformed cells using ligated folate as the targeting agent. Exploiting the cytotoxicity of the ribosome-inacitivating toxin, momordin, to assay successful intracellular protein delivery, we demonstrate that HeLa and KB cells (two malignant human cell lines) can be selectively and quantitatively killed in co-cultures with WI38 and Hs67 cells (two normal human cell types). Not only are the normal cells not damaged by treatment of the co-cultures with momordin-folate, but their rates of proliferation actually accelerate, presumably due to increased availability of nutrients otherwise consumed by the transformed cells. Analysis of folate receptor number before and after momordin-folate treatment indicates that receptor density may be a good predictor of toxin-folate sensitivity. Taken together, the data suggest that conjugates of folic acid with cytotoxic proteins warrant further examination as possible tumor-specific chemotherapeutic agents.

ISSN:1061-186X    

DOI:10.3109/10611869409015898

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractThe heterogeneity of tumour antigen expression, the differential sensitivity of individual cells to drugs and the use drug - antibody immunoconjugates with limited potency can limit the antitumour effects of immunoconjugate therapy. In this study we have used two different antibodies linked to two different drugs Melphalan (Mel) and Idarubicin (Ida), each with a different site action, to evaluate the potential of using cocktails of immunoconjugates. A series of drug combinations were screened for their synergistic activityin vitrousing the inhibition of [3H]-thymidine uptake by E3 cells, and constructing isobolagrams: Mel plus Ida was the only combination found to be synergisticin vitroand this synergism extended to the drugs after conjugation to antibodies. In addition,in vivostudies in mice bearing E3 tumours showed that synergy between both free drugs and between Ida-anti-Ly-2.1 and N-AcMEL-anti-Ly-3.1 immunoconjugates was time dependent, requiring treatment with Ida or Ida-MoAb conjugates prior to the addition of the second melphalan containing immunoconjugate. The use of two different antibodies, anti-Ly-2.1 and anti-Ly-3.1 against E3 (Ly-2.1+ve, Ly-3.1+ve) gave greater synergyin vitrocompared to using only one antibody. Again a cocktail of two antibody immunoconjugates provided significantly greater antitumour efficacy when given to tumour bearing mice, provided that the Ida-anti-Ly-2.1 was given 24h before injection of N-AcMEL-anti-Ly-3.1. The enhanced antitumour effect was not observed when the immunoconjugates were given simultaneously, or if the same antibody was used in each conjugate. Of importance was the finding that although the anti-tumour effect was synergistic, there was no increase in toxicity noted. The increased therapeutic index observed by using a double cocktail (2 antibodies + 2 drugs) could have major implications for immunoconjugate therapy.

ISSN:1061-186X    

DOI:10.3109/10611869409015899

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractA prodrug of 5-aminosalicylic acid (5-ASA), salicylazosulfanilic acid (SASA), which consists of sulfanilic acid linked to 5-ASA through an azo-linkage was newly synthesized. Biopharmaceutical properties of SASA were evaluated in comparison with those of salicylazosulfapyridine (SASP) in rats. Since SASA is much more hydrophilic than SASP, the absorption of SASA from the small intestine was less in comparison with SASP. When SASA and SASP were incubated with the rat intestinal contents under anaerobic conditions, both compounds were stable in the small-intestinal contents, but were rapidly degraded to 5-ASA in the cecal and the colonic contents. The degradation to 5-ASA by the large-intestinal contents was suppressed by the pretreatment with kanamycin sulfate, suggesting that the bioconversion of SASA is mediated by the intestinal microflora similarly to that of SASP and that SASA is also a prodrug of 5-ASA. After the oral administration, 5-ASA was found neither in the stomach nor in the small intestine in case of both prodrugs. Most of the prodrugs were transferred to the lower intestine where they were degraded to 5-ASA. The recovery of SASA including the metabolites from the gastrointestinal tract at four hours after the oral administration was significantly greater than that of SASP. Accordingly, SASA is free from the liberation of sulfapyridine, the adverse effect moiety of SASP, and less absorbable in the small intestine. Thus, the beneficial characteristics of SASA as an excellent colon-targeted prodrug of 5-ASA were clarified.

ISSN:1061-186X    

DOI:10.3109/10611869409015900

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractTime-Controlled Explosion System (TES) has the time-controlled drug release property with a predesigned lag time. The drug release from the system is initiated by destruction of the membrane. In this study, metoprolol tartrate was used as a model drug. After five types of TES with differentin vitrolag times were orally administrated to dogs, plasma metoprolol concentration was monitored. There existed a good correlation betweenin vitroandin vivolag time, while the extent of absorbed metoprolol decreased with prolongation of lag time. Next, thein vivodrug release behavior was directly investigated using five different colored TES with a lag time of two hours. Each TES was consecutively administrated to the fasted dogs at predetermined intervals. The amount of metoprolol released was monitored by recovering the administered TES from the gastrointestinal trace. Thein vivorelease profile corrresponded with thein vitroone. It is demonstrated that TES can release the drug inin vivoconditions similarly toin vitro.Based on these results, the decrease of the absorption is suggested to be caused by increased hepatic first-pass metabolism of the drug due to the retarded release rate with longer lag time.

ISSN:1061-186X    

DOI:10.3109/10611869409015901

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractIn the elimination of injected liposomesin vivo, it is considered that several serum components play an important role on hepatic uptake of them. This study was conducted to clarify the hepatic uptake mechanism of cetylmannoside (Man)-modified multilamellar vesicles (Man-MLV) using perfused rat liver. In the presence of serum, Man-MLV was taken up by the liver depending on the serum concentration, and it showed an approximately two-fold higher accumulation than MLV without any surface modifications (PC-MLV). These heptic uptakes of liposomes were obviously inhibited by preheating the serum at 56°C for thirty minutes or by the treatment with anti-rat C3 antiserum. Further, SDS-PAGE followed by immunoblot analysis showed the deposition of iC3b on the opsonized Man-MLV. These results obtained in the present study suggested that hepatic uptake of Man-MLV was mainly mediated by complement receptor rather than mannose receptor on Kupffer cellsin vivo.

ISSN:1061-186X    

DOI:10.3109/10611869409015902

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractUptake by nasal epithelial tissue of fluorescent polystyrene latex microparticles of diameter 0.8μm was studied in rats after single intranasal dosing. At intervals following administration, particles were observed in the blood compartment. Peak concentration of particles occurred in normal animals at lOmin. At 24 h some particles were still present in these animals' circulation. Throughout the sampling, tracheotomised animals demonstrated a steady state presence of particles. These results show that the uptake and translocation of solid particles does also take place through the nasal epithelial lining as it does through gut epithelia, possibly through the nasal associated lymphatic tissue.

ISSN:1061-186X    

DOI:10.3109/10611869409015903

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractUptake by gut epithelial tissue of 60 nm polystyrene particles was studied in female Sprague-Dawley rats (180g, 9 weeks old) after 5 days oral dosing by gavage (14mg/kg). The gut was divided into lymphoid and non-lymphoid tissue of the small and large intestine, prior to analysis for polystyrene by gel permeation chromatography (GPC). Approximately 10% of the administered dose was recovered from the entire gastrointestinal tract. The total percentage of the administered dose taken up through lymphoid tissue was statistically much greater than through non-lymphoid tissue. It was estimated that 60% of the uptake in the small intestine occurred through the Peyer's patches, even though the patches comprised a small percentage of the total surface area of the small intestinal tissue. A significant amount of the total uptake was shown to occur in the large intestine, particularly in the lymphoid sections of this tissue. These results were confirmed by fluorescence microscopy.

ISSN:1061-186X    

DOI:10.3109/10611869409015904

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractThree types of bovine serum albumin (BSA) derivatives such as lactosylated BSA (LBSA), mannosylated BSA (Man-BSA), and cationized BSA (cBSA) were synthesized and their hepatic disposition characteristics in mice were evaluated by pharmacokinetic analysis. At lower doses (≤1 mg/kg), LBSA and Man-BSA were very rapidly eliminated from the blood circulation due to uptake by parenchymal and nonparenchymal cells of the liver, respectively,viareceptor-mediated endocytosis (Nishikawa et al., 1992; Nishida et al., 1991a, b). These uptake processes were nonlinear and the apparent hepatic uptake clearances (CLliver) were decreased at administered doses higher than 1 mg/kg, e.g. 10, 20, and 100mg/kg. The liver accumulation of cBSA was also nonlinear, but its binding and/or uptake capacity in the liver was larger than those of LBSA and Man-BSA; i.e., CLliverdecreased at doses higher than 20mg/kg. In the next step, we modified these BSA derivatives by attaching polyethylene glycol (PEG), a modifier known to reduce the hepatic uptake and increase plasma retention, to achieve precise control of thein vivodisposition characteristics of BSA derivatives. By conjugation with PEG having a molecular weight of 10kDa, the CLlivervalues of LBSA, Man-BSA, and cBSA were decreasing to one-seventh, one-fortyfifth, and one-onehundredthirtieth, respectively. However, liver accumulation of PEG modified LBSA and Man-BSA at 24h after i.v. injection was not significantly different from unmodified BSA derivatives. These results suggest that it is possible to control the hepatic uptake of protein drugs by a combination of introduction of charge or sugar moieties and PEG conjugation.

ISSN:1061-186X    

DOI:10.3109/10611869409015905

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractThe influence of the aminoterminal substituent in a homologous series of tetrapeptide analogs on transport across Caco-2 cell monolayers was studied. In a series of pyridylcarboxamide regioisomers, the 2-pyridyl isomer was significantly more permeable than either the 3- or 4-congeners. The uniqueness of this peptide was further suggested by examining the partitioning behavior between heptane and ethylene glycol, a system which has been developed as a simple estimate of the desolvation energy or hydrogen bonding potential of a peptide. In this model, the 2-isomer has a much larger partition coefficient than either the 3- or 4-analogs, consistent with its being less solvated than expected based on simple structural considerations. Factors possibly contributing to this decreased effective polarity could be steric interactions or intramolecular hydrogen bonding.

ISSN:1061-186X    

DOI:10.3109/10611869409015906

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor