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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.

The thermal characteristics of poly (DL-lactic acid) (DL-PLA) microspheres containing a hexapeptide (NA: H(CH3)-Arg-Lys-Pro-Trp-tert-Leu-Leu-OEt) with neurotensin activity were investigated. PLA microspheres with a drug content of 1.5-11.0% were prepared by a novel o/w (oil-in-water) solvent evaporation method. Both DL-PLA and NA were amorphous in form, and an increase in heat capacity at glass transition temperature (Tg) of the polymer was observed in DL-PLA microspheres containing NA. The Tg of DL-PLA (PLA2000 bulk) was 307.8 K, while Tg of microspheres containing NA (content 6.0%) shifted to 321.2 K. The Tg of PLA2000 microspheres was found to increase with an increase in the content of NA, and its increasing tendency reached a plateau at an NA content of greater than 6%. The apparent activation energy of glass transition of PLA2000 bulk and the microspheres was calculated to be 86.3 and 99.3 kcal/mol, respectively. As a result of the release test after storage at 4 degrees C and 40 degrees C for 1 month, nearly the same release profiles of NA from PLA2000 microspheres were found. The release rate of NA after the initial release became slow after storage at 45 degrees C for 1 month. This may be attributed mainly to a decrease in surface area caused by the formation of agglomerates of PLA2000 microspheres under conditions near Tg.

Quantitative structure-activity relationships of a series of perfluorochemicals (PFCs) for use as oxygen transporters were investigated in terms of their in vivo half-lives (t1/2). The logt1/2 values can be correlated by a linear combination of lipophilic (e.g., critical solution temperature (CST)), physicochemical (e.g., molecular weight and vapor pressure (Pv)) and topological (e.g., number of fluorines (NOF)) parameters on regression analyses. The most important excretion-rate-determining factor was the CST. The Pv alone of PFCs did not correlate well with logt1/2. However, a combination of CST and Pv produced the most meaningful and important correlation, indicating that Pv plays a pivotal role in the excretion and can be considered a kind of correction factor to the CST. The t1/2 can thus be predicted from the combination of CST and Pv. It can also be predicted from structural information : the smaller the NOF, the shorter the t1/2. The incorporation of hetero atom (s) such as nitrogen and oxygen in the PFC molecule, which has been considered to produce better emulsion stability but results in persistence in the body, had relatively little effect in terms of t1/2. These results suggested that, taking the emulsifiability of hetero atom-containing PFCs into consideration, a cyclic F-ether and F-tertiary amine with fused ring (s), containing fewer fluorines than acyclic analogues, might be a good candidate compound as an oxygen transporter.

Spectrofluorometric studies using 1-anilino-8-naphthalenesulfonate (ANS) reveal that Z-fraction from rat liver has far the more hydrophobic binding sites than the other cytoplasmic binding fractions X and Y. Diagnostically important organic anions, such as sulfobromophthalein (BSP) and rose bengal (RB), are shown to displace ANS from Z-fraction by quenching the fluorescence of ANS and Z-fraction mixture without the change of quantum yield and emission maximum. The binding constants of these dyes to Z-fraction are determined by the competitive studies with ANS, and are coincident with those from other methods. Since the spectrophotometric technique reveals that the number of RB binding sites on Z-fraction is about twice as large as that of ANS binding sites, ANS and RB do not have necessarily the identical binding sites, though they must have partly common ones. The major binding force between organic anions and Z-fraction is supposed to be hydrophobic considering that the binding constant of Z-fraction for ANS is only about one-eight of that of bovine serum albumin (BSA) of which site is both hydrophobic and cationic. This property of sites accounts for the lower affinity for BSP of Z-fraction extracted from CCl4 chronically intoxicated rats, which our former study has made clear.

Route dependence of area under blood (or plasma) concentration curve (AUC) of drug, or first-pass effect was considered based on a generalized perfusion model where drug is supposed to be disposed in liver and kidney. The results verified the Gibaldi's equation based on a three compartment model to describe the route dependence with hepatic blood flow and hepatic clearance. From this consideration, the equation to described and to predict the dose dependence of AUC with urinary excretion and only one blood concentration at a steady state during a constant infusion was proposed and verified experimentally. And further the correspondence of the generalized perfusion model to a multi-compartment mammillary model for AUC was discussed and the equation for the route dependence was proposed in the case in which drug circulates through enterohepatic system and is disposed in small intestine as well as in liver and kidney.

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.

Two morphologically different crystals, column-shaped and ramified, were sorted under a microscope from a recrystallized batch of 5-nitroacetylsalicylic acid. Their degradation rates in the solid state were quantitatively studied and the progress of decomposition was observed under a polarizing microscope. Plots of the ratio decomposed against the reaction time were sigmoidal under all reaction conditions, and Avrami's kinetic equation was applicable to this reaction below 40% degradation. The reactivity of the ramified crystals was greater than that of the column-shaped crystals under all experimental conditions. Although the parameter B of Avrami's equation, which is assumed theoretically to be proportional to the product of the number of latent reaction nuclei and the voluminal growth rate varied by a factor of 104 at maximum under various experimental conditions, the ratio of B between ramified and column-shaped crystals remained fairly constant under all the conditions tested, and was about five. The results of observation of the decomposing crystals under a polarizing microscope agreed well with Avrami's theory of the formation and growth of reaction nuclei.

Physicochemical properties of the purified leucine amino peptidase from Aspergillus japonica were studied. The molecular weight of this enzyme was estimated to be approx. 31100 by sedimentation equilibrium, and the sedimentation coefficient (S20, W) was determined to be 3.12 S. The extinction coefficient at 278.5 nm, E1%1cm was 7.72 and the isoelectric point was at around pH 8.0 by gel electrofocusing. The helical content was calculated to be 1.7% from the Moffit-Yang plots. The amino acid analyses indicated that the enzyme was composed of 289 amino acid residues and contained one cystine. The amino-terminal amino acid was lysine, and the partial specific volume calculated from amino acid composition was 0.726.

Kinetics studies were performed on the non-enzymatic decomposition of glutathione (GSH) in anaerobic aqueous solution. The apparent first-order rate constants of decomposition were determined in the pH range of 1-12, ionic strength 0.5, at 60° and the pH profile was constructed from the buffer-free rate constants and pH values. The decomposition of GSH took place rapidly in acidic solution, but the rate constant showed a minimum in the pH range of 5-6, a maximum at pH 8.5 and a plateau in the pH range of 10-12. The effects of ionic strength and dielectric constant were almost negligible. The apparent activation energies of decomposition of GSH were all in the range of 19-21 kcal/mol. The rate constants of decomposition were related to the mole fractions of ionic species of GSH, and could be expressed as a function of hydrogen ion activity at arbitrary pH.

The fate of 8-hydroxyquinoline (Oxine) (OX) in rats, which is the parent compound of iodochlorhydroxyquin (chinoform, 5-chloro-8-hydroxy-7-iodoquinoline) (I) suspected to cause SMON, was investigated. Although both OX and I are metabolized to glucuronide and sulfate, the differences obtained from the excretion data are as follows : 1) After the intravenous administration of OX, glucuronide was more excreted (about 65% of dose) than sulfate (about 25% of dose) in urine in contrast to the case of I. 2) In bile, only 10% as glucuronide was excreted. The difference from I was considered due to the difference of molecular weight caused by the halogen substitution. 3) Both OX glucuro nide and sulfate were stable in the body, and it was excreted as the administered form without exchanging to the another form after the intravenous administration of each conjugate. Accordingly the fate of these compounds in the body was shown to be well influenced by the halogenation. Furthermore, the blood concentration of free and conjugated OX, which was determined with synthesized 14C-OX, was analyzed by the application of numerical deconvolution technique to the precursor-successor relationship between OX and each conjugate. Consequently, the usefulness of the technique was demonstrated and some pharmacokinetic features for OX were obtained.

The pharmacokinetics of riboflavin-5'-phosphate (FMN) and the metabolite riboflavin (FR) in the rat was studied with measurement of the plasma levels after the injection into femoral and portal vein of the FMN dose of 1 and 10 mol. Area under the curve (AUC) of FR plasma level vs. time after FMN injection into portal vein was found to be larger than the case of femoral vein. This route dependency of AUC in active metabolite was successfully explained from viewpoint of the compartment theory of linear pharmacokinetics. The AUC of FR was also varied by the dose of FMN. This dose dependency was analyzed to be the decrease in total clearance of FR with increasing FMN dose. The model dependent rate constants in FMN and FR pharmacokinetics did not vary with the dose and route but the distribution volume of FR did. The per cent of FR excreted in bile and urine in 24 hours after injection of FMN did not vary with the dose and route of FMN injection.

Dimethyl sulfoxide (DMSO) effect on the alkaline hydrolysis rate of amide was studied. Among seven amides studied, i.e., benzamide, p-nitrobenzamide, N-methyl-p-nitrobenzamide, acetanilide, N-methylacetanilide, N, N-dimethylbenzamide and N, N-dimethyl-p-nitrobenzamide, DMSO increased the rates of the last two N, N-dimethylamides, and decreased the rates of the other five amides. Since DMSO increased the ester alkaline hydrolysis rates with desolvation of hydroxide ion, the rate determining step in N, N-dimethylbenzamides hydrolysis was assumed to be the OH- addition to carbonyl carbon as in ester. And in the other five amides, the rate determining step was assumed to be the leaving of amino group from the tetrahedral intermediate. This assumption was supported by pH dependence of DMSO effect on 2, 2, 2-trifluoro-N-methylacetanilide hydrolysis of which rate determining step depends on hydroxide ion concentration. From this standpoint, as DMSO decreased the hydrolysis rates of hexobarbital and thiamylal, the rate determining step of barbitals was considered to be C-N bond fission.

The kinetic investigation about the factors affecting the biliary excretion was tried with azo and indigoid dye in rat. Five azo dyes, i.e., Azorubin S, Amaranth, New Coccine, Ponceau R, Ponceau SX, and Indigo Carmine as indigoid dye were used. (1) All dyes except New Coccine used here began to be excreted within 2-5 min and the peak of the excretion rate appeared between 10 and 20 min after administration. But as for New Coccine which had the very low excretion ratio, the delay of the excretion was observed and the peak of the excretion rate was hardly observed. (2) The dose dependency of biliary excretion which had been found in riboflavin was also found in dyes, and accordingly, the dependency was considered not to be specific to a biological substance such as riboflavin. (3) In the excretion rate constant, all dyes which showed high dose type excretion pattern had two rate constants k1 and k2 as shown in riboflavin, and the ratios of them were between 1.4 and 3. (4) It was also found that not only the number of sulfonate groups, but also the position of them had an effect on the biliary excretion ratio. (5) The biliary excretion pattern of Indigo Carmine which is likely to be excreted in urine was not different essentially from those of azo dyes of which the ratio was high.

1) Attempt was made to suppress the hydrolysis of acetylsalicylic acid with anionic (sodium laurylsulfate), cationic (cetylethyldimethylammonium bromide and benzalkonium chloride), and nonionic (Emulgen 120) surfactants. The hydrolysis of the undissociated form of acetylsalicylic acid is suppressed by the three kinds of surfactants and that of the anionic form is suppressed by cetylethyldimethylammonium bromide and benzalkonium chloride. 2) Through the ultraviolet spectra and the partition coefficient, it was ascertained that the undissociated form of acetylsalicylic acid is solubilized with the above three kinds of surfactants and the anionic form interacts with only a cationic surfactant.

The disappearance of ethoxybenzamide from a rabbit plasma after an intravenous injection was studied. 1. The distribute phase after the injection could not be neglected, and the two compartmental model was applied to analize the time course of plasma concentration. 2. The iterative least square method with a digital computer was proposed to obtain pharmacokinetic constants and their statistical values. 3. The present method gave the unique parameters independent of personal error for drawing straight lines in the semilogarithmic plots of plasma concentration vs. time, and it could test the adoptability of data for the model.

1) Sodium lauryl sulfate (SLS) was hydrolysed in acidic solution at a high temperature, and the rate of hydrolysis was dependent on not only H+ concentration but also SLS. concentration. It was recognized that the rate of reaction was increased strikingly in the region of a certain concentration of SLS. 2) When the Critical micelle concentration (CMC) of SLS was determined by solubilization method with dye (Sudan III), it was approximately coincident with region of a certain concentration where the rate of reaction increased strikingly. 3) On the contrary to acidic solution, in alkaline solution, SLS above the CMC was a little more stable than that of below.

In the previous papers, the authors reported the kinetic studies on the factors affecting the biliary excretion using Azo, Indigoid and Triphenylmethane dyes. The further study was tried using Xanthene dyes, Fluorescein and Bromsulphthalein, and the effect of halogenation was discussed. Four Xanthene dyes, i.e. Eosine Y, Phloxine B, Erythrosine B, Rose Bengal, and Fluorescein and Bromsulphthalein were used. (1) The excretion behaviors were similar to those of Azo and Triphenylmethane dyes which had the dose dependency, but the excretion ratios showed common larger values than 75% except Fluorescein which had no halogen group. (2) It was found that the halogen group had great influence on the biliary excretion as well as the sulfonate group. And it was also suggested that the effect of halogen group depended on the total electro negativity of substituents. And furthermore it was found that the increasing in molecular weight had not so much effect than the increasing of polarity. (3) It was also suggested that the -I gave the delay of excretion in the early period and this was probably due to the larger uptake into liver cells. (4) BSP showed markedly concentrical excretion pattern and large excretion ratio in a short period and it was found that these characteristic behavior was mainly ascribed to both halogen groups and sulfonate groups.

The processes of uptake of TPD (thiamine propyl disulfide) and formation of thiamine were investigated in detail, using the suspension of rat erythrocytes, since erythrocytes were most effective to form thiamine from TPD in blood. 1) The ratio of amount of thiamine formed in erythrocytes to that in the suspension medium was 1 : 1 after incubation of TPD in erythrocytes suspension. This ratio did not change remarkably, even when amount of erythrocytes was increased by 100 fold. 2) It was verified that TPD was converted to thiamine in the membrane under the influence of reducing compounds in erythrocytes and thiamine, which was formed there, went out and into erythrocytes with equal probability. 3) Process of formation of thiamine from TPD by erythrocytes was expressed by second order rate reaction kinetics, and its rate constant was determined.

Dependence of biliary excretion behavior of a quaternary ammonium compound on administration route was reported. When valethamate bromide or scopolamine-N-butyl bromide was infused through portal vein at a constant rate, it produced a higher biliary excretion rate and total excreted amount than when they were infused through femoral vein at the same rate. This phenomenon was discussed to estimate the availability of an absorbed drug from a small intestine with biliary excretion data when the excretion data of the intravenously administered drug was taken as the standard which corresponded to the complete absorption. That is, if the dependence is overlooked, the estimated availability from biliary excretion data would be overestimated, because a drug through portal vein was more excretable than that through femoral vein.

In the previous paper, the authors reported the kinetic studies on the factors affecting the biliary excretion with azo dyes and indigoid dye. The further investigation was tried with triphenylmethane dyes in rat. Six triphenylmethane dyes, i.e., Brilliant Blue FCF, Light Green SF, Fast Green FCF, Guinea Green B, Acid Violet 6B and Acid Violet 5B were used. (1) The excretion behaviors were similar to those of azo dyes which had the dose dependency. And the excretion ratios were generally larger than those of azo dyes except Light Green SF and Acid Violet 5B. (2) It was concluded that a sulfonate group beyond other groups had a remarkable effect on the biliary excretion ratio and pattern, and that the position of a sulfonate group as well as the number was important to determine its effect. (3) The possibility of the compartmental analysis for the biliary excretion process was suggested in the excretion pattern of Brilliant Blue FCF.

Promotion of the rectal absorption of antipyrine by sodium caprate (CA-Na) and diethyl maleate (DEM) was examined by in situ recirculating perfusion in the rat and compared with the results obtained previously with sodium ethylenediaminetetraacetate (EDTA-Na), a paracellular promoter. Both CA-Na and DEM significantly increased antipyrine absorption clearance (CLAP)and water inflex, in the same way as EDTA-Na. The increased levels of both CLAP and water influx caused by CA-Na were reduced to the control levels by ouabain, as was also found in the case of EDTA-Na. However, the promoting effect of DEM was decreased only slightly (not significantly) by ouabain treatment. These results indicate that the promotion mechanisms of CA-Na and DEM are different and that CA-Na works as a paracellular promoter in a manner similar to EDTA-Na.Antipyrine absorption through the paracellular route may possibly be promoted by water absorption dependent on active sodium transport.

1) The prevention of hydrolysis of ester, using methantheline bromide (Banthine) as an example, with surfactants was examined. Surfactants used were anionic, cationic, and nonionic. Anionic surfactant (sodium laurylsulfate) markedly prevented the hydrolysis (the half life becomes 100 times longer in 0.5% laurylsulfate solution) and nonionic surfactant prevents it slightly. 2) Hydrolysis in sodium laurylsulfate solution does not follow a pseudo-first order course and is influenced by a buffer concentration. 3) The higher the concentration of sodium laurylsulfate, the slower became the hydrolysis.