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Biomedical subjects

S Awazu

Publications and source records attributed to S Awazu.

At least 91 records · Page 5Linked to original sources
PubMed1991

Effect of carrier-mediated transport system on intestinal fosfomycin absorption in situ and in vivo.

Intestinal absorption mechanism of fosfomycin (FOM), a water-soluble and small molecular antibiotic, at the clinical dose level was examined by both in situ single-pass perfusion technique of rat small intestine and oral administration in rat in vivo. Analyzing the luminal concentration-dependence of FOM absorption rates in situ by the equation composed of two terms of carrier transport of Michaelis-Menten type and simple-diffusion, apparent Michaelis constant (Kt), maximal transport velocity (Jmax), and first-order diffusive absorption clearance (Kd) were 1.13 mM, 2.54 nmol/min/cm length, and 0.551 microliters/min/cm length, respectively. At the low FOM concentration in the lumen (0.1 mM), its absorption was reduced to about 60% of the control by inorganic phosphate ion at 1.0 mM in the same manner as the uptake in brush border membrane vesicles of rat small intestine (BBMVs) in vitro. Both the glycol form of FOM at 10 mM, the hydrolyzed metabolite of FOM in the stomach juice, and FOM itself at 10 mM reduced FOM absorption by about 50%, indicating the metabolite to be transported by the same carriers as those of FOM. At the higher FOM concentration (5 mM), its absorption was not reduced by any inhibitor described above. No inhibitory effect of 50 mM phosphate ion on FOM absorption following the oral dosing of 20 mg/kg FOM was found. It was concluded that FOM absorption at the clinical dose (10-20 mg/kg) is barely inhibited by the carrier-mediated system via phosphate transport system observed in the in vitro BBMVs.

Animals↗
PubMed1990

Purification and characterization of three ribonucleases from human kidney: comparison with urine ribonucleases.

Three ribonucleases (RNases) with different molecular masses were isolated from human kidney. The enzymes were purified to an electrophoretically homogeneous state, and their respective molecular masses were found to be 18,000 (tentatively named RNase HK-1), 20,000 (RNase HK-2A), and 22,000 (RNase HK-2B) on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Analysis of the amino acid compositions, amino-terminal sequences, and enzymological properties of the enzymes indicate that RNase HK-1 is related to "nonsecretory" RNase, and that RNases HK-2A and HK-2B are both related to "secretory" RNase. Furthermore, RNase HK-1 showed cross-reactivity with an antibody specific to nonsecretory RNase from human urine, whereas RNases HK-2A and HK-2B showed cross-reactivity with another antibody specific to human urine secretory RNase. However, the carbohydrate compositions of RNases HK-2A and HK-2B were markedly different from that of the secretory urine RNase. This finding seems to indicate that the kidney is not the origin of the urine enzyme.

Adult↗
PubMed1990

Heterogeneity of rat plasma albumin and drug binding.

Rat plasma albumin fractionated by Sephadex G-75 (superfine) gel filtration from freshly prepared rat plasma was further separated into three major fractions by chromatofocusing column chromatography. All the fractionated albumins had high binding affinity for the fluorescent probe 8-anilino-1-naphthalenesulfonic acid, as the model compound for acidic drugs, and were found to be immunologically identical.

Anilino Naphthalenesulfonates↗
PubMed1990

Human genetically polymorphic deoxyribonuclease: purification, characterization, and multiplicity of urine deoxyribonuclease I.

A deoxyribonuclease I was purified from the urine of a 46-year-old male (a single individual) by using a series of column chromatographies to a homogeneous state as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme was found to be a glycoprotein, containing 1 fucose, 7 galactose, 10 mannose, 6 glucosamine, and 2 sialic acid residues per molecule. The N-terminal amino acid sequence up to the 27th residue of the enzyme was similar to that of pancreatic deoxyribonuclease I from bovine and other species. The catalytic properties of the enzyme derived from a single individual closely resembled those of deoxyribonuclease I purified from human urine collected from several volunteers [Ito, K. et al. (1984) J. Biochem. 95, 1399-1406]. The purified enzyme was found to consist of multiple forms with different pI values. These findings are compatible with the existence of genetic polymorphism of deoxyribonuclease I in human urine previously reported [Kishi, K. et al. (1989) Hum. Genet. 81, 295-297]. This multiplicity of the urine enzyme might be due to variations in the primary structure and/or differences in the content of sialic acid.

Amino Acid Sequence↗
PubMed1990

Correlation of phenol sulphotransferase activities in the liver and platelets of rat.

Phenol sulphotransferase (PST) activity in rat platelet cytosol for p-nitrophenol (PNP) sulphation was found to have a similar dependence on PNP concentration and thermostability to that in rat liver cytosol. The activities of PST isoenzyme for the sulphation in the microM range of PNP in rat platelets and rat liver were significantly correlated. Thus, measurement of PST activity in platelets could be a useful and practical method for predicting this activity in liver.

Animals↗
PubMed1990

Prediction of glycyrrhizin disposition in rat and man with liver failure by a physiologically based pharmacokinetic model.

Two physiologically based pharmacokinetic models A and B incorporating enterohepatic recycling, which succeeded previously in predicting the disposition of glycyrrhizin (GLZ) in normal rats and subjects, were applied to predict GLZ disposition in plasma and tissues of chronically CCl4-intoxicated rats, and serum of humans with hepatitis after i.v. dosing. The prediction by model A with the direct excretion of GLZ from liver into gut lumen gave fairly good agreement with the observed time courses of GLZ concentrations in blood and tissues in the intoxicated rats. The human serum disposition was predicted by model B, to which was added a gallbladder for the excretion from liver into gut lumen to model A by assuming continuous delaying transfer from the gallbladder. An attempt to predict the serum dispositions in five human subjects by considering individual differences in serum free fraction, biliary excretion ratio, and intestinal absorption clearance was successful in model B. Thus, scale-up of the disposition kinetics of GLZ from rat to man with liver failure was successful.

Animals↗
PubMed1990

Prediction of glycyrrhizin disposition in rat and man by a physiologically based pharmacokinetic model.

Three physiologically based pharmacokinetic models A--C, incorporating enterohepatic recycling, were developed to predict glycyrrhizin (GLZ) disposition in rat plasma and tissues, and human serum. Model A, which included fourteen compartments (artery, vein, tissues except brain, and gut lumen) with the assumption of direct excretion of GLZ from the liver into the gut lumen gave fairly good agreement between the observed and predicted disposition profiles in rat, but was unsuitable in man, where elimination is very rapid. Models B and C for man were obtained by adding a gallbladder compartment (drug storage organ) for the excretion from the liver into the gut lumen and by assuming continuous transfer from the storage compartment or instantaneous emptying from it during meal ingestion as the excretion process from the gallbladder into the gut lumen, respectively. The agreement between the observed and predicted serum concentration time-course profiles was better with model C than model B, especially in the terminal elimination phase, where secondary peaks appeared. However, it was thought that the observed serum disposition can be sufficiently well predicted by model B. In conclusion, prediction in rat was successful in all compartments except the brain, which shows a negligible distribution. Scale-up of the disposition kinetics of GLZ from rat to man was also successful.

Animals↗
PubMed1990

Vitamin A protects the small intestine from methotrexate-induced damage in rats.

A protective effect of vitamin A (VA) against cytotoxic antitumor drug-induced damage of rat small intestine was found. Oral administration of methotrexate (MTX) for the small intestinal mucosa of rats resulted in a severe histological change, whereas rats coadministered VA with MTX showed a histological status similar to that of control rats. The p.o. administration of MTX led to a decrease in the amounts of membrane proteins and lipids in rat small intestine and its brush border membrane. When administered p.o. with VA, this decrease failed to occur. The brush border membrane of MTX plus VA-treated rats, when monitored by the fluorescence of cationic safranin O and anionic 8-anilino-1-naphthalenesulfonic acid, was found to resemble that from control rats rather than that from MTX-treated rats. The in vitro permeation of MTX in the small intestine of MTX plus VA-treated rats was enhanced, in contrast with the decrease noted for MTX-treated rats. However, that of untreated rats was not affected by the presence of VA. Thus, VA is unlikely to affect the transport process of MTX directly. When administered p.o. with VA, MTX was absorbed effectively to the same or a slightly greater extent than when administered by itself. Consequently, it has been shown histologically, biochemically, physicochemically and physiologically that VA protects the small intestine from the damage induced by MTX.

Administration, Oral↗
PubMed1989

Genetic polymorphism of human urine deoxyribonuclease I.

A genetic polymorphism of human urine deoxyribonuclease I (DNase I) has been detected by the technique of polyacrylamide gel isoelectric focusing (IEF-PAGE) followed by immunoblotting with anti-DNase I antibody. Family studies showed that the three common phenotypes - DNASE1 1, 1-2, and 2 - and the other four rare phenotypes - DNASE1 1-3, 2-3, 2-4, and 3-4 - represent homozygosity or heterozygosity for four autosomal codominant alleles, DNASE1*1, *2, *3, and *4. The frequencies of the DNASE1*1, DNASE1*2, DNASE1*3, and DNASE1*4 alleles in a studied Japanese population were 0.5453, 0.4396, 0.0117, and 0.0034, respectively.

Deoxyribonuclease I↗
PubMed1989

Time dependent changes occurring in rat liver microsomes upon lipid peroxidation.

Steady-state fluorescence anisotropy of diphenylhexatriene and n-(9-anthroyloxy)stearic acids (n = 2,12) in rat liver microsomes showed a marked increase in the early stages of enzymatically or non-enzymatically induced lipid peroxidation. The changes in fluorescence anisotropy occurred in parallel with the formation of thiobarbituric acid-reactive substances (TBA-RS). Parallel to these changes, the fluorescence emitted from peroxidized microsomes increased markedly in the early stages of lipid peroxidation. In contrast to the changes in the fluorescence anisotropy and in the formation of TBA-RS, the fluorescence showed a continuing increase over the three hr period of lipid peroxidation. Glucose-6-phosphatase was inactivated in the early stages of lipid peroxidation, whereas NADH-cytochrome b5 reductase underwent a slow deactivation over three hr. The apparently slow deactivation of the peripheral protein may be explained by the formation of fluorescent substances.

Animals↗
PubMed1989

Protection of liver microsomal membranes from lipid peroxidation by garlic extract.

Garlic extract, the ethanol-soluble fraction of garlic, prevented formation of thiobarbituric-acid-reactive substances and fluorescent substances during lipid peroxidation of rat liver microsomes. Lipid peroxidation increased the fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene labelled to the microsomes while this increase was prevented by the garlic extract. It thus seems probable that the garlic extract serves to maintain membrane fluidity. These effects were dependent on its concentration and particularly prominent on exceeding a certain concentration of garlic extract. These results suggest its possible role of protecting the membranes from lipid peroxidation.

Animals↗
PubMed1989

Change in small intestinal brush border membranes of rats following methotrexate administration.

Change in small intestinal brush border membranes of rats following methotrexate administration was monitored by the fluorescence spectra and polarization of the cationic fluorescent probe, safranin 0. Total protein content of brush border membranes of treated rats was less than that of control rats, whereas no significant difference in total sialic acid content of brush border membranes was observed between them. Thus, an apparent increase in the electronegative charge of brush border membrane vesicles per unit of membrane protein following methotrexate administration may possibly cause the change in fluorescence spectra and polarization of safranin 0.

Animals↗
PubMed1989

Effect of serum on dose- and temperature-dependent hepatic uptake of multilamellar vesicles (MLV).

Effects of the addition of serum to the perfusate on hepatic uptake of multilamellar vesicles (MLV) were examined in recirculating perfused rat liver. MLV was labelled with both membrane lipid marker ([14C]cholesteryl oleate) and aqueous phase marker ([3H]inulin or 5(6)-carboxyfluorescein (CF)). The uptake rates of [14C]cholesteryl oleate and CF at 37 degrees C coincided well, indicating both markers to be taken up as MLV. Inulin was released from MLV at 37 degrees C but its uptake rate tended to approach that of [14C]cholesteryl oleate at 4 degrees C or at high MLV dose. Some factor in serum promoted MLV uptake at 37 degrees C, but its effect was inhibited at 4 degrees C. The promoting effect was indicated to be possibly due to activation of adsorption of MLV to the hepatic Kupffer cell surface and/or that of phagocytosis by the cells. The saturation of MLV uptake was observed with increase in MLV dose, suggesting the saturation of MLV adsorption to the hepatic cell or the consumption of serum factor which promotes MLV uptake.

Animals↗
PubMed1989

Paracellular channel characterized by non-electrolyte permeation through the colonic membrane of the rat.

The mucosa-to-serosa permeability of non-electrolytes through the stripped colonic rat mucosa was examined in a Ussing-type chamber. The permeation clearances for inulin (12-15 A radius) to erythritol (3.2 A radius) increased linearly with the increase in their free diffusion coefficients. On the other hand, the clearances of glycerol, thiourea and urea of less than 3 A radius increased in excess of what would be expected considering the above linearity. This suggests that there are large pores that do not restrict diffusive flow and small pores of 3 A radius or greater that restricted diffusion in the paracellular channel. The transcellular permeation also occurred in a tracer efflux experiment with urea preloaded in colonic stripped mucosa. It was not ruled out that the higher permeability of the nonelectrolytes less than 3 A in radius was due to a transcellular route in parallel with the paracellular one.

Alcohols↗
PubMed1989

Binding of glycyrrhizin to human serum and human serum albumin.

The binding of glycyrrhizin (GLZ) to human serum and human serum albumin (HSA) was examined by an ultrafiltration technique. Specific and nonspecific bindings were observed in both human serum and HSA. The association constants (K) for the specific bindings were very similar: 1.31 x 10(5) M-1 in human serum and 3.87 x 10(5) M-1 in HSA. The number of binding sites (n) and the linear binding coefficient (phi) in HSA were 1.95 and 3.09 x 10(3) M-1, respectively. When the human serum protein concentration was assumed to be 4.2% (equal to the measured serum albumin concentration), n in human serum was 3.09, which is similar to the n value in HSA, and phi in human serum was 0.71 x 10(3) M-1, which is reasonably close to that for HSA. The binding pattern of GLZ with human serum protein on Sephadex G-200 column chromatography showed that GLZ binds to only the albumin fraction. It was concluded that the GLZ-binding sites in human serum exist mainly on albumin and GLZ binds to specific and nonspecific binding sites at lower and higher concentrations than approximately 2 mM, respectively.

Glycyrrhetinic Acid↗
PubMed1989

Pharmacokinetics of glycyrrhetic acid, a major metabolite of glycyrrhizin, in rats.

The pharmacokinetics of glycyrrhetic acid (GLA) was examined in rats after bolus i.v. injection at a dose of 2, 5, or 12 mg/kg. The decline in plasma concentration was generally biexponential at each dose, but the terminal disposition became much slower with increase of dose. A greater than proportional increase in plasma GLA concentration was observed with increase of dose, suggesting a dose-dependency of GLA disposition. Apparent total body clearance decreased significantly with increase of dose. On the other hand, the apparent steady-state distribution volume after i.v. administration was unaffected by dose. The plasma disposition at each dose fitted well to a two-compartment pharmacokinetic model with Michaelis-Menten elimination. It was concluded that the pharmacokinetics of GLA in the rat is dose-dependent owing to a saturable elimination rate. The plasma level of GLA after glycyrrhizin (GLZ) i.v. dosing (100 mg/kg) in the control rats (without biliary fistulization) sustained the concentration range of 1.5-3 micrograms/ml during 1-48 h, but that in the rats with biliary fistulization declined with time. It was suggested that the sustained plasma level of GLA is accounted for by the intestinal reabsorption of GLA produced from GLZ and GLA-conjugates during the enterohepatic recycling of both.

Animals↗
PubMed1988

Fluorescence study of the membrane-perturbing action of sodium caprylate as related to promotion of drug absorption.

The medium-chain fatty acid sodium caprylate released 6-carboxyfluorescein (CF), a model compound of water-soluble drugs, from the rat small intestinal brush border membrane (BBM) vesicles and liposomes containing CF. Caprylate caused a decrease in the fluorescence polarization of dansyl chloride, fluorescein isothiocyanate, and eosin maleimide covalently labeled to BBM. This indicates a perturbation of the BBM. However, no change in the fluorescence polarization of lipid-soluble fluorescent probes (2-(9-anthroyloxy) stearic acid, 12-(9-anthroyloxy) stearic acid, and 1,6-diphenyl-1,3,5-hexatriene) labeled to BBM was produced by caprylate. These findings indicate that caprylate can increase the permeability of the plasma membranes through the perturbation of the membranes. These actions of caprylate on membranes are considered one possible mechanism by which it promotes the absorption of water-soluble and poorly absorbed drugs.

Animals↗