Effects of cholesterol feeding on the distribution, metabolism, and accumulation of pentachlorobenzene in rats.

Umegaki, Keizo; Ichikawa, Tomio

doi:10.3177/jnsv.35.291

Cited by 5 publications

(4 citation statements)

References 15 publications

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“…The decrease in fat tissue mass reduces its capacity to store PECB there, increases PECB concentrations in the blood and liver, and thus accelerates PECB metabolism by the hepatic drug-metabolizing enzymes. This is supported by the facts that blood concentrations of PECB on days 1-2 and PCP on days 1-4 in the restricted diet groups were significantly higher than those in the AD group (Tables 3 and 5), and that the biological half-life of PECB in rats was approximately one day (18). These phenomena were quite similar to those observed in an experiment using young and adult rats (9).…”

Section: Discussionsupporting

confidence: 79%

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Effects of Restricted Feeding on the Absorption, Metabolism, and Accumulation of Pentachlorobenzene in Rats.

Umegaki¹,

Ikegami²,

Ichikawa³

1993

Journal of Nutritional Science and Vitaminology, J Nutr Sci Vit

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SummaryTo investigate the effect of restricted feeding (RF) on the absorption, metabolism, and accumulation of pentachlorobenzene (PECB), rats were fed either ad libitum (AD) or a restricted diet (at 25 or 50% of AD) for 15 days. On the 7th day (day 0), PECB (15mg/rat) was orally administered. Daily fecal weight and the total amount of PECB excreted into feces were decreased by RF, indicating an increase in PECB absorption due to its prolonged retention in the gastrointestinal tract. However, the amount of PECB excreted was only 4.8% of the dose given to the AD group, and 2.1 and 2.4% of that given to the 50 and 25% restricted diet groups, respectively. The concentrations of PECB and pentachlorophenol, and major metabolite, in blood of the restricted diet groups were higher on day 2 and day 4, while lower on day 6 and day 8 than those of the AD group. On day 8, PECB in liver, kidney, brain, and fat tissue were also lower in the restricted diet groups; the PECB levels in such tissue in the 25 and 50% restricted diet groups were 10-40 and 5-11% of that in the AD group, respectively. These results indicate that PECB metabolism was increased by RF. As PECB is lipophilic, it is most likely that the fat tissue mass, which was markedly decreased by RF, contributed to the enhancement of PECB metabolism. The mechanism seemed to be as follows: as fat tissue mass accumulating PECB decreased, the concentration of PECB in the liver increased, thus the amount of PECB metabolites formed was increased. Key Words pentachlorobenzene, absorption, accumulation, metabolism, fat tissue, food restriction, rat, pentachlorophenol Various organochlorine chemicals are present in the environment such as pesticides, herbicides, and intermediate products. These chemicals are lipophilic and tend to accumulate in fat tissue for a long time without being metabolized. The mobilization of such a chemical from the fat tissue into the blood is an important step toward its metabolism in the liver and its excretion from the body. Restricted feeding (RF) and fasting lead to decreased fat tissue mass, thereby mobilizing the chemical from the fat tissue together with lipolysis and enhancing its metabolism in the liver. In addition, it has been reported that RF treatment influences the activity of the hepatic drug-metabolizing enzymes (1, 2). The effects of RF on the excretion of DDT (3, 4), hexachlorobenzene (5, 6), and hexachlorobiphenyl (7, 8) have been tested. However, the results of these reports are inconsistent. In some cases, RF effectively enhanced chemical metabolism and excretion, but in other cases the treatment led to the redistribution of the chemicals, especially from fat tissue to the brain, and increased their toxicity. In most of these studies, the effect of RF was examined after the administration of the chemicals. RF prior to the administration of the chemicals might greatly influence both the transit time of the chemicals and fat tissue mass. The transit time might affect the absorption of the chemicals in the gastrointestinal tract,...

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Section: Discussionsupporting

confidence: 79%

“…PECB accumulated in fat tissue because of its lipophilic properties, whereas PCP could not be detected in fat tissues (18). Therefore, the transformation of PECB to PCP by cytochrome P®450 seems to be an important step in the excretion of PECB accumulated in the body.…”

Section: Discussionmentioning

confidence: 98%

Effects of Restricted Feeding on the Absorption, Metabolism, and Accumulation of Pentachlorobenzene in Rats.

Umegaki¹,

Ikegami²,

Ichikawa³

1993

Journal of Nutritional Science and Vitaminology, J Nutr Sci Vit

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“…As the concentration of hepatic fats, especially triglycerides, was high in the lard group (Table 2), the degree of interac tion of HCB with the hepatic drug-metabolizing enzymes might have been reduced, resulting in the impaired metabolism of HCB. We have observed similar findings using PECB (22,33). These findings in the lard group suggest that both the decrease in fat tissue mass and the interaction of HCB with hepatic drug-metabolizing enzymes were responsible for the increase of HCB metabolism in the fish oil group.…”

Section: Discussionsupporting

confidence: 76%

Feeding Fish Oil to Rats Accelerates the Metabolism of Hexachlorobenzene.

Umegaki

Ikegami

1998

Journal of Nutritional Science and Vitaminology, J Nutr Sci Vit

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SummaryThis study was conducted to examine the influence of dietary fat on the metabolism and excretion of hexachlorobenzene (HCB), a ubiquitous food contaminant which is metabolized at a low rate. Three groups of rats were fed semi-purified diets containing 10g/100g of either soybean oil, lard or fish oil for 2wk and then given a single dose of HCB by intragastric gavage. The concentrations of HCB and pentachlorophenol (PCP), a major metabolite of HCB, were monitored in the blood for 5d. Fecal excretion of HCB did not differ among the three groups, indicating no difference in HCB retained in the body among the groups. Concen trations of HCB in blood, liver and brain samples from the lard and fish oil groups, the members of which had a low fat tissue mass, were con sistently higher as compared with those in samples from the soybean oil group. The concentration of PCP and the PCP/HCB ratio in the blood were higher in the fish oil group than in the other groups. In addition, the amount of PCP excreted in urine was highest in the fish oil group. The hepatic cytochrome P-450 content in the fish oil group was higher than that in the other groups. These findings indicate that feeding fish oil to rats accelerated HCB metabolism. An increase in hepatic HCB concentration due to a small fat tissue mass and high hepatic cytochrome P-450 content may have played a role in accelerating HCB metabolism in the fish oil group.

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“…A previous study indicated the involvement of cytochrome P-450 3A in the microsomal oxidation of HCB to pentachlorophenol (PCP) and to tetrachlorobenzoquinone (TCBQ) (Van Ommen et al, 1989). PECB is also relatively rapidly metabolized and is oxidized to the same products as in the metabolism of HCB, that is, PCP and TCBQ (Besten et al, 1989;Umegaki and Ichikawa, 1989). Both compounds have been reported to be hepatotoxic and immunotoxic and to affect thyroid hormone homeostasis (Carlson and Tardiff, 1976;Vos et al, 1979;Besten et al, 1993).…”

Section: Introductionmentioning

confidence: 99%

Masking of Guar Gum-Induced Acceleration of Hexachlorobenzene Excretion by Its Rapid Excretion through Lactation in Adult Female Rats

Nakashima

Ohsawa

Umegaki

et al. 1998

J. Agric. Food Chem.

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The effect of dietary fiber and polyunsaturated fatty acids on the excretion of an ingested stable, lipophilic environmental pollutant was investigated in nonpregnant and pregnant rats fed hexachlorobenzene (HCB) diet (10 µg/100 g of diet). Nonpregnant rats ingesting guar gum, with polyunsaturated fatty acid for 4 weeks after an HCB diet period for 2 weeks, had lower perirenal fat mass as well as total amount of HCB found in such fat compared with cellulose-ingesting groups (P < 0.05). A large proportion of HCB in dams disappeared from the dams during the 15-day lactation period and was transferred to their suckling pups through the milk in both dietary fiber groups. No significant difference in total amount of HCB in suckling pups was observed whether the dams ingested cellulose or guar gum diet during the lactation period. It was concluded that the excretion of HCB into milk was so rapid that the guar gum-induced acceleration of its excretion from the dams were masked.

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Effects of cholesterol feeding on the distribution, metabolism, and accumulation of pentachlorobenzene in rats.

Cited by 5 publications

References 15 publications

Effects of Restricted Feeding on the Absorption, Metabolism, and Accumulation of Pentachlorobenzene in Rats.

Effects of Restricted Feeding on the Absorption, Metabolism, and Accumulation of Pentachlorobenzene in Rats.

Feeding Fish Oil to Rats Accelerates the Metabolism of Hexachlorobenzene.

Masking of Guar Gum-Induced Acceleration of Hexachlorobenzene Excretion by Its Rapid Excretion through Lactation in Adult Female Rats

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