Hirokazu Katayama

Solute Absorption from the Airways of the Isolated Rat Lung. IV. Mechanisms of Absorption of Fluorophore-Labeled Poly-α,β-[N(2-Hydroxyethyl)-DL-Aspartamide]

The pulmonary absorption kinetics of a single molecular weight distribution (MWD) of fluorophore-labeled poly-α,β-[N(2-hydroxyethyl)-DL-aspartamide] (F-PHEA), a hydrophilic and biocompatible synthetic polypeptide, were studied in the isolated, perfused rat lung (iprl) as functions of administered polymer concentration, dose, vehicle, and presence and absence of fluorophore. The MWD was characterized before and after absorption by measurement of weight- and number-averaged molecular weights (Mwand Mn, respectively) using high-performance gel-permeation chromatography. Values for Mw and Mn were 8.6 and 5.3 kD before, and 6.7 and 4.7 kD after, absorption into the perfusate; there was no significant metabolism and the MWD of the absorbed polymer was independent of both dose and sampling time over a 3-hr period. F-PHEA failed to show any evidence of aggregation in solution or changes in dose distribution within the airways as functions of increasing polymer concentration and dose. A concentration ranging study indicated the presence of a saturable, carrier-mediated transport process for F-PHEA with a maximum absorption rate, Vmax, of approximately 180 µg or 0.027 µmol/hr. Coadministration of fluorophore-free PHEA was capable of depressing the absorption of F-PHEA. The transport process for F-PHEA appeared to have a molecular weight limit of about 7 kD for this hydrophilic polymer.

Mechanism underlying insulin uptake in alveolar epithelial cell line RLE-6TN

For the development of efficient pulmonary delivery systems for protein and peptide drugs, it is important to understand their transport mechanisms in alveolar epithelial cells. In this study, the uptake mechanism for FITC-insulin in cultured alveolar epithelial cell line RLE-6TN was elucidated. FITC-insulin uptake by RLE-6TN cells was time-dependent, temperature-sensitive, and concentration-dependent. The uptake was inhibited by metabolic inhibitors, cytochalasin D, clathrin-mediated endocytosis inhibitors, and dynasore, an inhibitor of dynamin GTPase. On the other hand, no inhibitory effect was observed with caveolae-mediated endocytosis inhibitors and a macropinocytosis inhibitor. Intracellular FITC-insulin was found to be partly transported to the basal side of the epithelial cell monolayers. In addition, colocalization of FITC-insulin and LysoTracker Red was observed on confocal laser scanning microscopy, indicating that FITC-insulin was partly targeted to lysosomes. In accordance with these findings, SDS-PAGE/fluoroimage analysis showed that intact FITC-insulin in the cells was eliminated with time. The possible receptor involved in FITC-insulin uptake by RLE-6TN cells was examined by using siRNA. Transfection of the cells with megalin or insulin receptor siRNA successfully reduced the corresponding mRNA expression. FITC-insulin uptake decreased on the transfection with insulin receptor siRNA, but not that with megalin siRNA. These results suggest that insulin is taken up through endocytosis in RLE-6TN cells, and after the endocytosis, the intracellular insulin is partly degraded in lysosomes and partly transported to the basal side. Insulin receptor, but not megalin, may be involved at least partly in insulin endocytosis in RLE-6TN cells.

Application of curdlan to controlled drug delivery. I. The preparation and evaluation of theophylline-containing curdlan tablets.

To study the use of curdlan, a natural β-l,3-glucan, in drug delivery, in vitro release studies were carried out with curdlan tablets containing theophylline. Tablets were readily prepared by compressing three different curdlan and theophylline mixtures, namely, a physical mixture, spray-dried curdlan particles with theophylline powder, and spray-dried particles of curdlan/theophylline solution. Drug release from the tablets prepared from spray-dried particles of curdlan/theophylline was lowest. The release rate was constant from 1 to 8 hr, and 59% cumulative release was obtained at 8 hr. Drug release from curdlan tablets was unaffected by pH or various ions; these curdlan tablets might also control drug release in vivo after oral administration. Application of Higuchis equation indicated that drug release from curdlan tablets was diffusion-controlled. The release profiles of the curdlan tablets were compared to those of a commercial theophylline sustained-release tablet.

Drug release from directly compressed tablets containing zein

AbstractThe tablets prepared by the direct compression of spray-dried particles of a drug and zein were evaluated in vitro. The release of drug from the tablets was retarded compared with drug powder alone and tablets prepared from the physical mixtures. Drug release from the tablets was controlled by changing drug content and tablet, weight.

Airway Retention and Pulmonary Absorption of Poly-α,β-[N(2-hydroxyethyl)-D, L-aspartamide]

Coarse aqueous sprays of the polymer, poly-α,β-[N(2-hydroxy ethyl)-D,L-aspartamide], (PHEA), containing a covalently bound fluorophore, ethyl carbonyl-6-aminofluorescein, were administered in doses ranging 2.2 through 3.6 mg to the airways of the isolated rat lung (IPRL). The polymer was characterized with number and weight averaged molecular weights of 5300 and 8600 Daltons, respectively. Transfer to the perfusate supplying the pul monary circulation was monitored with time in order to assess the polymers systemic absorption potential and the transferred molecular weight distribu tions (MWD). The polymer was absorbed at an apparently constant rate during each experiment. The MWD of absorbed material was characterized by gel permeation chromatography and found to be shifted toward lower molecular weights when compared to that of the administered polymer. Two hours after dosing, absorbed material had mean values for weight mean molecular weight, Mw = 6670 ± 526 Daltons and number mean molecular weight, Mn = 4680 ± 640 Daltons where the ranges are standard deviations in 8 IPRL prep arations. PHEA was not metabolized in the 3 h duration of an experiment and there was some tendency for the median molecular weight of the absorbed material to increase with time after administration. Results are discussed in the context of macromolecular delivery to the systemic circulation via the lung.

Effect of acute renal failure on the disposition of cefoperazone.

The effect of acute renal failure on the disposition of cefoperazone was investigated. Rats, 3 days after uranyl nitrate treatment, were used to model acute renal failure.