Behaviors of selenite and inorganic mercury and interaction of these compounds in rabbit blood were investigated after intravenous administration. The major portion of the materials, when administered alone, was initially present in the plasma, but the plasma levels decreased rapidly. Simultaneous administration of both compounds caused the elevation of their levels in the erythrocyte. The radioactivity of both mercury and selenium in the erythrocyte showed relatively slow decay during the experiment, while that in the plasma decreased rapidly after a short stable phase of about one hour. Sephadex column chromatography of the stroma free hemolysate indicated an identical pattern of distribution of mercury and selenium as that observed in an in vitro study.

View full abstract

Enhancement of aniline hydroxylation was observed by the addition of cyanide in rat liver microsomes. The enhancing effect of cyanide on aniline hydroxylation activity was also observed in rabbit liver microsomes, but not in guinea pig liver microsomes. Aniline stimulated the reoxidation of reduced nicotinamide adenine dinucleotide (NADH)-reduced cytochrome b₅. The stimulation of cytochrome b₅ reoxidation by aniline was most remarkable in liver microsomes from desaturase-induced rats followed by that from fed and fasted rats. The increment in cytochrome b₅ reoxidation by aniline in all groups of rats was inhibited by the simultaneous addition of cyanide, However, the stimulatory effect of cyanide on aniline hydroxylation in fasted rat was not different from that observed in desaturase-induced rat. In addition, the effect of cyanide on aniline hydroxylation was suggested to be reversible.

View full abstract

The role of genipin in the choleretic action of geniposide, the principle component of gardenia fruit, was examined. Geniposide showed a delayed and prolonged action by intraduodenal administration of 1 g/kg or over, while genipin showed a fast choleretic action with 50 mg/kg. Geniposide did not show choleretic action after intraportal administration of 10-400 mg/kg but genipin showed a choleretic action with 2.5 mg/kg. Geniposide and genipin appeared in portal blood after intraduodenal administration of geniposide, while genipin appeared after intraduodenal administration of genipin. Genipin and genipin glucuronide appeared in the bile after oral and intraduodenal administration of geniposide and oral administration of genipin. Genipin and genipin glucuronide that appeared in portal blood and bile after administration of geniposide and genipin showed a periodical pattern similar to that of choleretic action of these two substances. These evidences indicate that the choleretic action of geniposide is due to genipin formed by hydrolysis of geniposide in the digestive tract.

View full abstract

Cinnamaldehyde increased contractile force and beating rate of the isolated perfused heart of guinea pigs. These effects were antagonized by propranolol and virtually abolished by reserpinization. Cinnamaldehyde released catecholamines from the isolated adrenal gland of dogs, whereas cinnamyl alcohol and cinnamic acid were devoid of such effect. Benzaldehyde also released catecholamines in the same preparation but its potency was lower than that of cinnamaldehyde. Cinnamaldehyde released catecholamines from the adrenals of pentobarbitalanesthetized and splanchnicotomized dogs by its close i.a. application to the organ, which was confirmed by measuring catecholamine contents in adrenal venous blood. Blood pressure in the same in situ preparation was raised by i.a. application of cinnamaldehyde and this pressor response was antagonized by phentolamine but not by combination of hexamethonium and atropine. When adrenal venous blood was taken out from the circulation immediately after an i.a. application of cinnamaldehyde, the pressor response was not observed in most cases. In conclusion, cinnamaldehyde released catecholamines from the adrenal gland of dogs through a direct action (independent of cholinergic receptor sites) on the organ, cinnamaldehyde was presumed to elicit positive ino-and chronotropic actions on the heart of guinea pigs by releasing endogenous catecholamines, and the aldehyde group in cinnamaldehyde molecule played a role in its catecholamine releasing effect from the organs.

View full abstract

Biotransformation of styrene (ethenylbenzene) into styrene glycol (1-phenyl-1, 2-ethanediol) via styrene oxide (phenyloxirane), a mutagen and skin carcinogen, by rat liver microsomes in the presence of an NADPH-generating system has been investigated. Both metabolites were identified by gas-chromatography-mass spectroscopy. In the microsomal system, styrene oxide appeared only after a brief incubation and disapeared thereafter in spite of the continued formation of styrene glycol. This phenomenon was rationally interpreted on the basis of previously obtained evidence that during aerobic incubations, NADPH-dependent microsomal lipid peroxidation decreased P-450 activities selectively to a remarkable extent compared with epoxide hydratase activities. Addition of 3, 3, 3-trichloropropene oxide, a potent epoxide hydratase inhibitor, to the incubation medium prolonged the biological half-life of styrene oxide significantly, indicating one of major factors determining the biological level of the mutagen to be the relative ratio of these enzyme activities.

View full abstract

When ¹⁴C-3-(5-nitro-2-furyl)-2-(2-furyl) acrylamide (AF-2) or ³H-methyl 3-(5-nitro-2-furyl)-2-phenylacrylate (MNFPA) was incubated with SH compounds such as cysteine and glutathione in purified milk xanthine oxidase-hypoxanthine system, the ethyl acetateextractable radioactivity from the reaction mixture was markedly decreased compared with the radioactivity obtained without the SH compound. When the radioactive water-soluble product from AF-2 was treated with 2, 4-dinitrofluorobenzene, considerable amounts of the radioactive product could be extracted with ethyl acetate from acidic but not alkaline solution. Furthermore, ³H-MNFPA and cysteine, and ¹⁴C-cysteine and MNFPA were incubated in the same enzyme system as above. After incubation, the water-soluble products were chromatographed on Amberlite XAD-2 columns and on silica gel thin-layer plates (n-butanol-acetic acid-water, 3 : 1 : 1) successively. As a result, the radioactive peaks of ³H and ¹⁴C were observed at the same Rf value of 0.53. These observations indicate that the active metabolites of AF-2 and MNFPA, which were produced during their enzymatic reduction, may react with the SH compounds such as cysteine and glutathione to form the water-soluble conjugates. The stoichiometry of reduction of these nitrofurans by the purified enzyme-xanthine system in the presence of cysteine showed that the active metabolites might be the hydroxylaminofurans. Two reduction products of MNFPA by partially purified milk xanthine oxidasehypoxanthine system were isolated and tentatively identified as methyl 6-cyano-4-oxo-2-phenyl-2-hexenoate and 3-(azacyclopenta-5-oxo-1, 3-dien-2-yl)-2-phenylacrylic acid.

View full abstract

The absorption and metabolism of p-aminobenzoic acid (PABA) was studied using the in vitro everted sac of rat intestine. PABA was metabolized to p-acetamidobenzoic acid (Ac-PABA) in the intestinal mucosa at the concentration of 5×10^-5 M PABA. The Ac-PABA formed was released into mucosal and serosal fluid. The mucosal disappearance rate of PABA and the formation of Ac-PABA showed a dose dependency in the concentration range from 3×10^-5 to 10^-3 M. The mucosal disappearance rate of Ac-PABA was much slower than PABA. Major N-acetyltransferase activity was found in the mucosal 9000×g supernatant fraction. High activity was found in both small and large intestinal mucosa. The small intestinal N-acetyltransferase of rat readily catalyzed the acetylation of PABA, p-aminohippuric acid, p-aminosalicylic acid, but was considerably less active towards sulfonamides. The significance of intestine as the metabolic organ was suggested in relation to the first-pass effect.

View full abstract

Rat small intestinal absorption of p-aminobenzoic acid (PABA) was investigated using the in situ recirculating and loop method. The disappearance of PABA from the lumen followed apparent first-order kinetics at lower initial concentration (10^-5 M), but showed a distributive phase at higher concentration (10^-3 M). A significant amount of p-acetamidobenzoic acid (Ac-PABA), the metabolite of PABA in the intestinal epithelial cell, was found in the intestinal lumen. The appearance of Ac-PABA in the lumen was dose dependent. At 10^-5 M PABA, more than 50% of dose was found in the lumen as Ac-PABA and at 10^-3 M PABA, nearly 10% of dose was found in the lumen as Ac-PABA after recirculation for 60 min. The induction of the distributive phase at higher dose could be ascertained by the analog computer simulation containing non-linear function. At higher dose, the enzyme in the intestinal mucosa was capacity limited and the free drug was accumulated in the cell and the distributive phase occurred. The appearance of metabolites in the lumen was also observed for p-aminosalicylic acid and p-aminohippuric acid. In addition, the disappearance of acetylated drugs from the lumen was much slower than the parent drugs. These observations suggested the metabolism of drugs in the intestine contributed significantly to the overall first-pass effect and also affected the absorption kinetics of drugs.

View full abstract

Hydrazine formation took place in man after the oral administration of isoniazid. The successive excretion of free hydrazine, one of the well-known mutagens, was observed in the urine of the patients on INH-treatment. The intact INH and the other metabolites, acetyl-INH, acetyl-hydrazine and diacetylhydrazine, were also analyzed by gas chromatography-mass spectrometry.

View full abstract

Significant correlations were observed between saliva and plasma concentrations of four kinds of aminopyrine metabolites as well as intact drug after a single oral administration of trideuterium-labeled aminopyrine to healthy adult males.

View full abstract