Ken-ichiro Minegishi

Distribution, metabolism, and excretion of musk xylene in rats

Distribution, metabolism and excretion of musk xylene (MX) were investigated in male Wistar rats. Urinary and fecal excretion accounted for 10 and 75% of the dose (70 mg/kg), respectively, on day 7 after orally administration of3H-MX to rats. Total residue of radioactivity in tissues on day 7 was less than 2.0% of the administered dose. The highest concentration was found in adipose tissue and the second was in liver. Some metabolites of MX were identified using GC-MS and NMR after purification by column or thin layer chromatography of feces, bile and urine extracts. MX, 2-NH2-MX, 2-Ac-MX, 2-NH2-3-CH2OH-MX, and 2-NH2-5-tert-BuOH-MX were found in feces, bile and urine. 4-NH2-MX and metabolite X were found in feces and urine. 4-NH2-3-CH2OH-MX was found in urine. HO-MX was found in bile. The major route of excretion for MX was the feces via bile. The reduction of the 2-nitro group of MX to the amino group was a key step in metabolism. Further metabolism of 2-NH2-MX may proceed by decreased steric hindrance of functional group.

Musk xylene is a novel specific inducer of cytochrome P-450IA2

The effect of musk xylene on contents of both cytochrome P-450IA1 and cytochrome P-450IA2 in rat liver was investigated using Western blotting analysis. Rats were treated i.p. for five consecutive days with either 50, 100 or 200 mg musk xylene/kg body weight. Musk xylene increased both total cytochrome P-450 and cytochrome b5 contents in rat liver microsomes. Musk xylene induced cytochrome P-450IA2 (384 pmol/mg protein) strongly and preferentially and the ratio of cytochrome P450IA2/P-450IA1 was about 12 at the lowest dose tested. Musk xylene also induced the cytochrome P-450IA1 dose-dependently, but these extents were very small (32-174 pmol/mg protein). These results suggest that musk xylene may be a more specific inducer for cytochrome P-450IA2 than any other inducers reported.

Isolation and identification of metabolites of 2-ethylhexyl diphenyl phosphate in rats

The metabolic fate of 2-ethylhexyl diphenyl phosphate (EHDPP) was studied in male rats. Orally administered 14C-EHDPP was rapidly absorbed and about 80% of the radioactivity was excreted in the urine and feces in the first 24 h. By 7 days, 48% and 52% of the radioactivity was recovered in urine and feces, respectively. Since biliary excretion was low (6% for 2 days), urine seems to be the major excretion route of EHDPP. Radioactivity was widely distributed in all tissues examined. At 2 h, the concentration was relatively high in blood, liver kidney and adipose tissue. The elimination of radioactivity from adipose tissue and liver was somewhat delayed, but almost all the radioactivity was eliminated by 7 days. The major metabolites in the urine were diphenyl phosphate (DPP) and phenol. p-Hydroxyphenyl phenyl phosphate (OH-DPP) and monophenyl phosphate (MPP) were also identified as minor metabolites.

Characterization of skin-surface lipids from the monkey (Macaca fascicularis)

Skin-surface lipids from the monkeyMacaca fascicularis are composed of sterol esters (38%), cholesterol (4%) and two types of wax diesters, identified as Type II (IIa and IIb, 17% and 40%, respectively). Type IIa contained diesters of 1,2-alkanediols esterified with two molecules of long-chain (C14−C34) fatty acids having straight and branched chains. In the diesters IIa, fatty acids shorter than C19 predominated in position 1, and fatty acids longer than C20 predominated in position 2. Type IIb contained diesters of 1,2-alkanediols esterified with C4 and C5 branched-chain fatty acids (predominantly isovaleric acid) at position 1 and long-chain (C14−C27) acids, having straight and branched chains, at position 2. The shortchain acids were converted to 2-nitrophenylhydrazides and analyzed by high-performance liquid chromatography (HPLC). Ammonia chemical ionization (CI)-gas chromatography (GC)-mass spectrometry (MS) resolved the intact diesters IIb into 12 peaks corresponding to molecular weights ranging from 597 to 748, and showed that the molecular species, such as C21−C16−C5 (diol, fatty acid in position 2, fatty acid in position 1), C22−C16−C5 and C23−C16−C5, were prevalent. The fatty acids from both diesters were mostly (>98%) saturated. The 1,2-alkanediols from both diesters consisted of C16−C26 saturated straight- and branched-chain components. The acyl groups of sterol esters contained 86% C14−C34 branched-chain acids. The unsaturated fatty acids (5.4%) belonged to a straight-chain monoenoic series having extremely long chains (C18−C34). The branched-chain structures in the fatty acids and diols were iso and anteiso. These results show the species-specific profile for the skin-surface lipid synthesis.

Effect of sorbic acid feeding on peroxisomes and sorboyl-CoA metabolizing enzymes in mouse liver: Selective induction of 2,4-dienoyl-CoA hydratase

On the basis of the finding that sorbic acid (SA)-induced hepatoma was correlated with the depletion of reduced glutathione (GSH) in mouse liver (Tsuchiya et al., Mutation Res 130: 267-262, 1984), the possible conversion of SA to a metabolite which is reactive with SH-compounds was studied. Sorboyl-CoA was hydrated and then reduced to 3-keto-4-hexenoyl-CoA by the combined actions of mitochondrial hydratase (crotonase) and L-3-hydroxyacyl-CoA dehydrogenase. Upon the addition of GSH or coenzyme A, 3-keto-4-hexenoyl-CoA was nonenzymatically converted to another 3-ketoacyl-CoA derivative, possibly a Michael type adduct, in a time- and concentration-dependent manner. Alternatively, sorboyl-CoA can be reduced by 2,4-dienoyl-CoA reductase and completely beta-oxidized without the generation of 3-keto-4-hexenoyl-CoA. Two-week feeding of mice of 15% SA caused a 2.0-fold induction of peroxisome beta-oxidation in the liver. SA caused a marked induction (3.6-fold) of hydratase toward sorboyl-CoA but a less pronounced induction (1.3-fold) of 2,4-dienoyl-CoA reductase, leading to about a 3-fold elevation in the hydratase: reductase ratio. The elevated ratio was sustained throughout the period of SA feeding up to 12 weeks. Thus, a large amount of SA could be converted to 3-keto-4-hexenoyl-CoA during this period. Oxidative stress caused by a depleted cellular SH-pool together with the induction of peroxisome proliferation by SA-feeding may implicate the mechanism by which non-mutagenic SA caused hepatoma.

Metabolism of triphenylmethane colours II. Absorption, excretion and distribution of Benzyl Violet 4B (FD and C Violet No. 1) in rats.

Absorption, excretion and distribution of Benzyl Violet 4B were investigated in rats, deterimining the colour by the 2-wavelength technique. This colour was hardly absorbed when given orally; only 0.89% of the dose was recovered from the bile after 24 h. On the other hand, it was rapidly excreted through the bile when given intravenously; the cumulative recovery of biliary excretion amounted to 88.4% at 4 h and 95.9% at 24 h. The levels of the colour distributed in the liver, kidney abdominal muscle and blood serum were in the range of 1--3 microgram/g of tissue in rats fed a diet containing 5% Benzyl Violet 4B for 8 weeks, whereas they were slightly lower in rats fed the diet for 18 weeks. When rats were given the colour intravenously, there was no sex-related difference in the distribution of the colour in either Wistar or Sprague--Dawley rats, but the disappearance of the colour from the brain, liver, abdominal muscle, abdominal skin and ear of Sprague--Dawley rats was slower than from those of Wistar rats.

Metabolism of Triphenylmethane Colors (III)

Distribution and biliary excretion of Benzyl Violet 4B and Fast Green FCF were compared in female Sprague-Dawley rats after an oral administration of the 3H-labeled compounds.The levels of Benzyl Violet 4B distributed in the plasma, ear, abdominal skin and abdominal muscle were higher than those of Fast Green FCF. The cumulative amounts of Benzyl Violet 4B and Fast Green FCF excreted in the bile were 4.26 and 3.81% of the dose by 24hr, respectively. The biological half-lives for Benzyl Violet 4B in the above tissues were longer than those for Fast Green FCF.

Corticosterone Level of Blood Plasma and Demethylation Activity of the Liver after Pretreatment with Morphine and Phenobarbital in Rats.

When rats were orally given 500μmoles per kg of phenobarbital, the plasma level of corticosterone is not exhibited to be significantly changed. At 25 hours after pretreatment with phenobarbital, the activity of demethylation of methylbabital is markedly increased, but the demethylation of morphine and meperidine are not. The corticosterone level of plasma in rats which were pretreated with morphine intraperitoneally with a daily dose of 80 mg per kg was increased except the first day, while the activity of demethylation of meperidine and morphine was continued to decrease with chronic administration of morphine.