Biomedical subjects

H Sezaki

Publications and source records attributed to H Sezaki.

At least 55 records · Page 3Linked to original sources

PubMed1991

Absorption and metabolic characteristics of p-aminobenzoic acid and its isomer, m-aminobenzoic acid, from the rat small intestine.

Absorption and metabolic characteristics of p-aminobenzoic acid (PABA) and m-aminobenzoic acid (MABA) from the rat small intestine were examined by means of in situ recirculation and in vitro everted sac experiments. p-Aminobenzoic acid was extremely rapidly absorbed from the rat small intestine, whereas the absorption of MABA, the m-isomer of PABA, was comparably slower. This finding was partly explained by the result that PABA is more lipophilic than MABA. The metabolite percentage of PABA was considerably greater than that of MABA in mucosal fluid, tissue, and serosal fluid. On the other hand, a concentration-dependent and a directional difference in the transfer rate of these drugs were observed in everted and noneverted sacs of rat small intestine. Furthermore, mucosal uptake of PABA or MABA was inhibited by 1 mM 2,4-dinitrophenol, 10 mM sodium azide, and pretreatment with HgCl2 (10 mM). These results indicate that MABA, as well as PABA, is transported through the intestine by a carrier-mediated transport system, and that the molecular structure of these drugs is important for their absorption and metabolic characteristics.

4-Aminobenzoic Acid↗

PubMed1991

Assessment of drug disposition in the perfused rat brain by statistical moment analysis.

Drug disposition in the brain was investigated by statistical moment analysis using an improved in situ brain perfusion technique. The right cerebral hemisphere of the rat was perfused in situ. The drug and inulin were injected into the right internal carotid artery as a rapid bolus and the venous outflow curve at the posterior facial vein was obtained. The infusion rate was adjusted to minimize the flow of perfusion fluid into the left hemisphere. The obtained disposition parameters were characteristics and considered to reflect the physicochemical properties of each drug. Antipyrine showed a small degree of initial uptake. Therefore, its apparent distribution volume (Vi) and apparent intrinsic clearance (CLint,i) were small. Diazepam showed large degrees of both influx and efflux and, thus, a large Vi. Water showed parameters intermediate between those of antipyrine and those of diazepam. Imipramine, desipramine, and propranolol showed a large CLint,i compared with those of the other drugs. The extraction ratio of propranolol significantly decreased with increasing concentrations of unlabeled propranolol in the perfusion fluid. These findings may be explained partly by the tissue binding of these drugs. In conclusion, the present method is useful for studying drug disposition in the brain.

Animals↗

PubMed1991

Hepatic disposition characteristics of electrically charged macromolecules in rat in vivo and in the perfused liver.

The effect of electric charge on the hepatic disposition of macromolecules was studied in the rat. Charged derivatives of dextran (T-70) and bovine serum albumin (BSA), mitomycin C-dextran conjugates (MMC-D), and lactosaminated BSA (Lac-BSA) were employed as model macromolecules. After intravenous injection, cationic macromolecules were rapidly eliminated from plasma because of their extensive hepatic uptake, while anionic and neutral macromolecules were slowly eliminated. Cationic macromolecules were recovered from parenchymal and nonparenchymal hepatic cells at a cellular uptake (per unit cell number) ratio of 1.4-3.2, while that of Lac-BSA was 14. During liver perfusion using a single-pass constant infusion mode, cationic macromolecules were continuously extracted by the liver, with extraction ratios at steady-state (Ess) ranging between 0.03 and 0.54, whereas anionic and neutral macromolecules were almost completely recovered in the outflow at steady state. The Ess for cationized BSA (Cat-BSA) and cationic MMC-Dcat were concentration dependent and decreased at low temperatures and in the presence of colchicine and cytochalasin B. The possible participation of the internalization process in the uptake of cationic macromolecules by hepatocytes was suggested.

Animals↗

PubMed1991

Hepatic disposition characteristics of 111In-labeled lactosaminated bovine serum albumin in rats.

The hepatic disposition of lactosaminated bovine serum albumin (Lac-BSA) in rats was studied at the whole body, isolated liver, and isolated parenchymal cell levels. After intravenous injection, 111In-Lac-BSA (1 mg/kg) was rapidly eliminated from the plasma due to extensive uptake by liver parenchymal cells; however, a significant decrease in hepatic clearance was observed at high dose (50 mg/kg). In a single-pass, constant infusion experiment in the isolated liver, 111In-Lac-BSA was continuously extracted. The extraction ratio at steady state (Ess) for 111In-Lac-BSA was significantly decreased by coadministrating galactose, NH4Cl, or chloroquine, and at low temperature, suggesting that hepatic uptake of Lac-BSA proceeds via receptor-mediated endocytosis for asialoglycoprotein. Kinetic analysis of 111In-Lac-BSA binding with isolated parenchymal cells at 4 degrees C yielded a dissociation constant (Kd) of 2.5 x 10(-8) M and a value of 3.5 x 10(5) maximal binding sites/cell (Bmax). The internalization rate constant (kint) for 111In-Lac-BSA was calculated to be 0.46 min-1 in liver perfusion experiments using the EDTA-wash method.

Animals↗

PubMed1991

Tumor localization and in vivo antitumor activity of the immunoconjugate composed of anti-human colon cancer monoclonal antibody and mitomycin C-dextran conjugate.

The tissue distribution and in vivo antitumor activity of a novel monoclonal antibody-mitomycin C conjugate (A7-MMCD) composed of anti-human MAb A7 and MMC-dextran conjugate were investigated using tumor-bearing mice. A7-MMCD was prepared via an anionic dextran intermediate for the purpose of keeping the non-specific uptake by the reticuloendothelial system to a minimum. 111In-labeled A7-MMCD showed about a 5-times-greater accumulation in SW1116 (targeted tumor) than in S180 (non-targeted tumor) 48 h after injection, and produced a tumor-to-blood ratio which was 3 times higher in SW1116-bearing mice than in S180-bearing mice 96 h after injection. Accumulations in the liver, spleen, and kidney were also observed to some extent. Pharmacokinetic analysis revealed that A7-MMCD had nearly the same properties in the body as MMCDan (MMCD with an anionic charge), i.e., those of a negatively charged macromolecule. Both A7-MMCD and MMCDan had relatively similar tissue uptake rate indices for the liver and spleen. The tumor uptake rate index for SW1116 was about 2.5 times greater than that for S180, and the total amount of 111In-A7-MMCD accumulated in SW1116 was calculated to be approximately 5 times greater than the amount in S180. These results indicated that A7-MMCD could achieve site-specific targeting in the body. Furthermore, in the therapeutic experiment using SW1116 implanted subcutaneously, A7-MMCD suppressed tumor growth significantly, compared to free MMC and MMCDan. These results suggest that in designing an monoclonal antibody-drug conjugate via an intermediary, the physicochemical properties of intermediate macromolecules must also be taken into consideration to obtain a high degree of efficacy in vivo.

Animals↗

PubMed1991

Transport of cephalexin to the cerebrospinal fluid directly from the nasal cavity.

The aim of the present study has been to confirm the existence of a transport pathway for a drug (cephalexin) to the cerebrospinal fluid (CSF) directly from the nasal cavity, by comparing the drug's concentrations in CSF after intranasal (i.n.), intravenous (i.v.) and intraduodenal (i.d.) administration. Higher levels of the drug were found in CSF following i.n. administration compared with the i.v. and i.d. routes, even though its plasma concentrations were similar. These findings suggest the existence of a direct transport pathway for cephalexin from the nasal cavity to the CSF. The concentration of drug in CSF at 15 min after i.n. administration was higher than that at 30 min. In contrast, its concentrations in CSF at 15 min after i.v. and i.d. administration were not significantly different from those at 30 min. The results confirm the presence of a direct transport pathway to CSF from the nasal cavity. This pathway may represent a new delivery route to CSF and possibly to brain parenchyma.

Administration, Intranasal↗

PubMed1991

The effect of immunization with protein-sulphanilic acid conjugate on sulphanilic acid disposition in the rat.

Rats were immunized with bovine gamma-globulin-sulphanilic acid conjugate and the plasma concentration of sulphanilic acid examined after an intravenous injection of this drug. There was a significant increase in plasma half-life and AUC and a significant decrease in clearance of sulphanilic acid in the immunized rats compared with the control. In the immunized rats, binding of sulphanilic acid to macromolecules in serum, determined by ultrafiltration, decreased with increase of sulphanilic acid concentration. At low concentrations, there was a significant increase in % binding of the drug in the serum of immunized rats compared with controls. There was also a significant reduction in urinary excretion of total drug in the immunized rats compared with controls. These findings suggest that sulphanilic acid-specific antibodies in the serum of immunized animals bind [14C]sulphanilic acid, giving rise to higher serum levels thereby making it unavailable for normal excretory processes.

Animals↗

PubMed1991

A new method for assessment of drug absorption from muscle: application of a local perfusion system.

Drug absorption from muscle has been examined using the rabbit hind leg, isolated by cannulating the femoral artery and vein, and perfused with or without bovine serum albumin (BSA) using a single-pass technique. A model compound, [14C]sucrose, was injected into the musculus gastrocnemius, and its appearance in the venous outflow was monitored and kinetically analysed by statistical moment theory. The fraction absorbed and mean arrival time in the venous outflow were calculated to be 103% and 50.5 min, respectively, in the BSA-containing system. The results of perfusion experiments without BSA were not significantly different, suggesting possible use of the simpler BSA-free perfusion system to obtain information on the muscular absorption of drugs.

Animals↗

PubMed1991

Tissue distribution of 111In-labeled uricase conjugated with charged dextrans and polyethylene glycol.

Uricase (UC) was conjugated with dextran, cationic diethylaminoethyl-dextran (DEAED), and anionic carboxymethyl-dextran (CMD) giving a molecular weight of 10000 by the periodate oxidation method. Their disposition characteristics were studied after intravenous injection (i.v.) in mice. Disposition of the conjugate with activated polyethylene glycol (PEG2) with a similar molecular weight was also studied for comparison. Tissue distribution of the 111In-labeled UC in these conjugates was evaluated by a tissue uptake clearance index calculated in terms of clearance. After i.v. injection, 111In-UC was slowly eliminated from the circulation and gradually accumulated in the liver, spleen, and kidney. Conjugation with neutral dextran slightly enhanced the uptake of 111In-UC by the liver and spleen, while PEG2 conjugation decreased the tissue uptake and resulted in extremely long plasma retention. On the other hand, DEAED and CMD conjugation resulted in significant enhancement and reduction of hepatic uptake, respectively. These results demonstrated that the pharmacokinetic behaviour of UC can be widely controlled by chemical modification with macromolecules having adequate physiochemical properties.

Animals↗

PubMed1991

The transport of a drug to the cerebrospinal fluid directly from the nasal cavity: the relation to the lipophilicity of the drug.

The objective of the present study was to clarify the relation between drug transport to the cerebrospinal fluid (CSF) from the nasal cavity and the lipophilicity of the drug using hydrophilic sulfonamides as model drugs. The nasal cavity of the rat was perfused in a single pass system and the concentrations of sulfonamides in plasma and CSF were measured. The drug concentrations in CSF and plasma after nasal perfusion were compared with those after intravenous (i.v.) administration. The drug concentrations in the CSF were remarkably high after nasal perfusion in comparison with those after i.v. administration, though the time course of the plasma concentration was not much different from that after i.v. administration. These results suggested the existence of a direct transport pathway of the sulfonamides from the nose to the CSF. In addition, the drug concentrations in the CSF increased with increasing the lipophilicity of the drugs (the partition coefficient (Pc) of the drugs between isoamyl alcohol and pH 7.4 phosphate buffer). A significant correlation was observed between the drug concentrations in CSF and Pc. In conclusion, the direct transport pathway of the sulfonamides from the nose to the CSF was confirmed and, with regard to drugs with comparatively low lipophilicity, the degree of the transport depended on its Pc.

Animals↗

PubMed1990

Disposition of anticancer drugs after bolus arterial administration in a tissue-isolated tumor perfusion system.

Disposition characteristics of various anticancer drugs in a tissue-isolated tumor preparation were studied in Walker 256 carcinosarcoma-bearing rats using an in situ single-pass vascular perfusion technique. Three anticancer drugs, 5-fluorouracil, mitomycin C, and Adriamycin, and two lipophilic prodrugs of mitomycin C were tested in the tumor preparation perfused with Tyrode's solution containing 4.7% bovine serum albumin. After bolus arterial injection of test drugs, their outflow concentration-time curves were analyzed based on statistical moment theory. In each tumor preparation, the injection of drug was paired with that of vascular reference substance, Evans' blue-labeled bovine serum albumin, and disposition parameters of the drug were corrected with those of vascular reference substance. From the mean transit time values of vascular reference substance, the average vascular volume of the tumor preparation was calculated to be 0.063 ml/g, which decreased with tumor growth. All drugs showed significant extraction by the tumor tissue, depending on their physicochemical properties. Distribution volumes of tested drugs were from 1.53 to 3.33 times larger than the vascular volume. Calculated intrinsic clearance values for the protein-unbound fractions increased as the lipophilicity of the drug increased. The potential increase in tumor uptake was observed in lipophilic prodrugs of mitomycin C. The present experimental system is thus suggested to be useful for analyzing drug disposition in tumor tissue.

Animals↗

PubMed1990

Effect of medium-chain glycerides on the intestinal absorption of phenol red: studies on mechanisms of the promoting effect.

To elucidate the mechanisms of the promoting action of medium-chain glyceride (MCG) on the intestinal absorption of phenol red (PR), the effect of different MCG dose levels on PR absorption, the absorption kinetics of MCG itself, and the mucosal reduced glutathione (GSH) levels were investigated to determine whether or not they are related to the promoting action of MCG. The absorption of PR was found to be enhanced with an increase in MCG dose (as an emulsion in the range 0.5-4.0%). Urinary excretion of PR was reduced by absorbed MCG components, which also resulted in an increase in the AUC. Moment analysis of plasma PR concentrations after intraintestinal administration revealed a shorter mean absorption time (MAT) for the emulsion formulation than for the control. The mucosal GSH level was lowered by the administration of the MCG emulsion (2-10%) into the intestinal lumen. Pretreatment with a 4% MCG emulsion decreased GSH levels to one-half of the control. In these cases, the level of mucosal GSH seemed to remain constant to the end of the experiment after it had decreased during the initial period. On the other hand, results from the in situ loop or recirculation study showed that enhancement of PR absorption appeared in the earlier period and then gradually decreased. The time course of the PR absorption rate, estimated from plasma concentration data, was similar to that of the MCG absorption rate. These results suggest that the promotion of intestinal absorption is related to the absorption kinetics of MCG itself, but not directly to the level of mucosal GSH.

Animals↗

PubMed1990

Disposition characteristics of macromolecules in tumor-bearing mice.

As part of the strategy for the design of macromolecular carriers for drug targeting, the disposition characteristics of macromolecules were studied in mice bearing tumors that served as target tissues. Eight kinds of macromolecules including four polysaccharides and four proteins with different molecular weights and electric charges were used; tissue distribution and tumor localization after intravenous injection were studied. Pharmacokinetic analysis revealed that the tissue radioactivity uptake rate index calculated in terms of clearance was different among the tested compounds; especially, the urinary radioactivity excretion clearances and the total hepatic radioactivity uptake clearances varied widely. Compounds with low molecular weights (approximately 10 kD) or positive charges showed lower tumor radioactivity accumulation; radioactivity was rapidly eliminated from the plasma via rapid urinary excretion or extensive hepatic uptake, respectively. On the other hand, large and negatively charged compounds, carboxymethyl dextran, bovine serum albumin, and mouse immunoglobulin G, showed higher radioactivity accumulation in the tumor (calculated total amounts were 15.6, 10.8, and 20.8% of the dose, respectively) and prolonged retention in the circulation. These results demonstrated that the total systemic exposure rather than the uptake rate index was correlated with total tumor uptake. Molecular weight and electric charge of the macromolecules significantly affected their disposition characteristics and, consequently, determined radioactivity accumulation in the tumor. It was concluded that a drug-carrier complex designed for systemic tumor targeting should be polyanionic in nature and larger than 70,000 in molecular weight.

Animals↗

PubMed1990

Intestinal transport of sulfanilic acid in rats immunized with protein-sulfanilic acid conjugate.

Intestinal transport of sulfanilic acid was examined by means of an in vitro everted sac technique in rats immunized with a bovine gamma-globulin-sulfanilic acid conjugate. At a low concentration of sulfanilic acid, the intestinal transport of sulfanilic acid was decreased in rats immunized with bovine gamma-globulin-sulfanilic acid conjugate. This phenomenon was dose dependent and antigen specific, since there was no difference in the transport of sulfanilic acid at a high concentration and of an unrelated hapten. These results suggested that parenteral immunization impaired not only the intestinal transport of macromolecular antigens, as previously shown, but also the transport of the low molecular weight hapten, sulfanilic acid.

Animals↗

PubMed1990

Percutaneous penetration of acyclovir through excised hairless mouse and rat skin: effect of vehicle and percutaneous penetration enhancer.

The effects of vehicle and percutaneous penetration enhancer on the penetration of acyclovir through excised hairless mouse and rat skin were investigated. Four solvents, propylene glycol (PG), ethanol (ET), isopropanol (IPA), and isopropyl myristate (IPM), were employed as vehicles, in combination with four enhancers, 1-farnesylazacycloheptan-2-one (7FU), 1-geranylazacycloheptan-2-one (7GU), 1-geranylazacyclopentan-2-one (5GU), and 1-dodecylazacycloheptan-2-one (Azone). Acyclovir was suspended in vehicles to avoid the effect of the thermodynamic activity of acyclovir in the vehicle. The penetration of acyclovir through hairless mouse skin from IPA was enhanced by 7GU, whereas that from IPM was not affected. All combinations of vehicle and penetration enhancer were examined using rat skin. No effect of the enhancers was observed in the IPM vehicle. The estimated solubility parameters of vehicles and enhancers indicated that the polarities of IPM and the enhancers are similar, which prevents effective penetration of the enhancers from IPM. However, the penetration of acyclovir from the other vehicles was increased by the enhancers. The combination of hydrophilic vehicle and hydrophobic enhancer resulted in a large enhancing effect. The disappearance of the enhancers from the vehicle correlated with their enhancing activity, but other factors also seemed to affect the penetration enhancement of acyclovir.

Acyclovir↗

PubMed1990

Biliary excretion of mitomycin C dextran conjugates in relation to physicochemical characteristics of carrier dextran.

Biliary excretion characteristics of polymeric prodrugs of mitomycin C (MMC), mitomycin C-dextran conjugates with cationic or anionic charge (MMC-Dcat, MMC-Dan) and with different molecular weights of dextran (10,000, 70,000, and 500,000) were studied in rat. Following intravenous injection, bile was periodically collected and concentrations of free and dextran-conjugated MMC in it were determined by bioassay. MMC administered as a free form was excreted rapidly into bile and 1.8% of the dose was recovered within 2 h. A small amount of MMC was gradually excreted into bile after administration of all MMC-Ds and total recovery at 8 h was less than 1% of dose. In this case, a major part of excreted MMC was recovered as a conjugated form. MMC-Dcat gave a larger total excretion of MMC than MMC-Dan and excretion was also affected by the molecular weight of carrier dextran. The biliary recovery of MMC-Dcat labeled with 14C at a spacer moiety was significantly higher than that of conjugated MMC determined by bioassay suggesting release and/or inactivation of MMC in MMC-D during the circulation in the body. These results were compared with biliary excretion of model macromolecules with the same molecular weight but different electric charge in order to clarify the effect of electric charge on the biliary excretion of macromolecules. Cationic macromolecules exhibited higher biliary excretion in relation to greater hepatic uptake.

Animals↗

PubMed1990

Effect of medium-chain glycerides on the membrane transport of D-glucose and sulfanilic acid in the intestinal brush-border membrane vesicles.

To clarify the influence of medium-chain glycerides (MCG) on a biological membrane, we investigated the membrane transport of D-glucose and sulfanilic acid in the brush-border membrane (BBM) vesicles pretreated with MCG. The size distribution of the BBM vesicles determined by electron microscopic observation was not significantly different between the vesicles incorporated with MCG and those of the control. However, the amount of D-glucose taken up by the vesicles at an equilibrated stage (30 min) was significantly decreased in the MCG-treated ones based on unit content of protein. Based on these results we estimated the membrane transport of D-glucose and sulfanilic acid in consideration of vesiculation or filter-capturing efficiency in MCG-treated vesicles. The rates of Na+ gradient-independent D-glucose transport and sulfanilic acid transport were significantly greater in MCG-treated vesicles than in the control. On the other hand, the magnitude of overshooting effect in Na+ gradient-dependent uptake of D-glucose in MCG-treated vesicles was maintained similar to the control. Comparison of kinetic parameters for active D-glucose transport at different concentrations indicated that Km and Vmax were not significantly different between MCG-treated and the control vesicles. These results indicated that passive diffusion of D-glucose and sulfanilic acid was significantly increased but Na(+)-glucose cotransporter was not significantly changed by the incorporation of MCG in the intestinal BBM vesicles.

Benzenesulfonates↗

PubMed1990

Biochemical and biopharmaceutical properties of macromolecular conjugates of uricase with dextran and polyethylene glycol.

Uricase (UC) was conjugated with dextran and polyethylene glycol and their biochemical and biopharmaceutical properties were studied. UC-dextran conjugates (UC-D) synthesized by four methods, periodate oxidation, cyanogen bromide, carbodiimide and cyanuric chloride largely retained the UC enzymatic activity depending on the extent to which they modified amino groups. The periodate oxidation method seemed best because it gave a conjugate with high yield and satisfactory activity retention. The conjugate of UC with activated polyethylene glycol (UC-PEG2) was also obtained with high yield but the remaining activity was somewhat lower than those of dextran conjugates at the same modification extent. UC-D and UC-PEG2 showed sustained enzymatic activity in plasma after intravenous injection to rats. The advantage of chemical modification of proteins, especially with dextran, by the periodate oxidation method for preparation of a protein-delivery system was thus suggested.

Animals↗