Abstract
It remains uncertain why non-genotoxic compounds that result in liver hypertrophy cause liver tumors. In an effort to resolve this issue, we examined whether liver postmitochondrial fraction (S9) prepared from rats treated with non-genotoxic compounds affected the genotoxicity of pro-mutagens. Known hepatotoxic compounds, such as piperonyl butoxide (PBO), decabromodiphenyl ether (DBDE), beta-naphthoflavone (BNF), indole-3-carbinol (I3C) and acetaminophen (AA),were orally administered to male and female F344 rats at doses sufficient to cause liver hypertrophy. Rats received diets containing each test compound for 3 days, 4 weeks or 13 weeks, and were then kept for 4 weeks without the test chemical. S9 prepared from the livers of each group was used for the Ames test with 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), benzo[a]pyrene (BaP) and N-nitrosodimethylamine (NDMA). In both sexes, liver hypertrophy was observed following administration of all test compounds, and was then reversed to the control state when administration ceased. The mutagenicity of MeIQx, BaP and NDMA increased with the use of S9 derived from rats treated with non-genotoxic compounds other than AA. DBDE administration had a marked effect on the mutagenicity of BaP (over a 30-fold increase in females) and NDMA (about a 20-fold increase in males). To estimate the involvement of metabolic enzymes in the alteration of mutagenicity, we measured the activity of ethoxyresorufin-O-deethylase (EROD) and methoxyresorufin-O-demethylase (MROD) (phase I enzymes), and UDP-glucuronosyltransferase (UGT) and glutathione S-transferase (GST) (phase II enzymes) in each S9 sample. The activity of phase I enzymes increased, even at the 3rd day following administration, and then decreased gradually, except in the case of AA, while the activity of phase II enzymes increased slightly. These results suggest that non-genotoxic hepato-hypertrophic compounds may be partly involved in carcinogenesis by modulating the metabolism of pre-carcinogens incorporated from the environment, in a manner that is dependent on sex and pre-incorporated chemicals.
| Original language | English |
|---|---|
| Pages (from-to) | 1-9 |
| Number of pages | 9 |
| Journal | Genes and Environment |
| Volume | 36 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - 2014 |
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Keywords
- Ames test
- Liver hypertrophic compound
- Metabolism
- Mutation
ASJC Scopus subject areas
- Genetics
- Environmental Science (miscellaneous)
- Social Psychology
Cite this
Effects of oral administration of non-genotoxic hepato-hypertrophic compounds on metabolic potency of rat liver. / Fang, Xing; Nunoshiba, Tatsuo; Yoshida, Midori; Nishikawa, Akiyoshi; Nemoto, Kiyomitsu; Degawa, Masakuni; Arimoto, Sakae; Okamoto, Keinosuke; Takahashi, Eizo; Negishi, Tomoe.
In: Genes and Environment, Vol. 36, No. 1, 2014, p. 1-9.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Effects of oral administration of non-genotoxic hepato-hypertrophic compounds on metabolic potency of rat liver
AU - Fang, Xing
AU - Nunoshiba, Tatsuo
AU - Yoshida, Midori
AU - Nishikawa, Akiyoshi
AU - Nemoto, Kiyomitsu
AU - Degawa, Masakuni
AU - Arimoto, Sakae
AU - Okamoto, Keinosuke
AU - Takahashi, Eizo
AU - Negishi, Tomoe
PY - 2014
Y1 - 2014
N2 - It remains uncertain why non-genotoxic compounds that result in liver hypertrophy cause liver tumors. In an effort to resolve this issue, we examined whether liver postmitochondrial fraction (S9) prepared from rats treated with non-genotoxic compounds affected the genotoxicity of pro-mutagens. Known hepatotoxic compounds, such as piperonyl butoxide (PBO), decabromodiphenyl ether (DBDE), beta-naphthoflavone (BNF), indole-3-carbinol (I3C) and acetaminophen (AA),were orally administered to male and female F344 rats at doses sufficient to cause liver hypertrophy. Rats received diets containing each test compound for 3 days, 4 weeks or 13 weeks, and were then kept for 4 weeks without the test chemical. S9 prepared from the livers of each group was used for the Ames test with 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), benzo[a]pyrene (BaP) and N-nitrosodimethylamine (NDMA). In both sexes, liver hypertrophy was observed following administration of all test compounds, and was then reversed to the control state when administration ceased. The mutagenicity of MeIQx, BaP and NDMA increased with the use of S9 derived from rats treated with non-genotoxic compounds other than AA. DBDE administration had a marked effect on the mutagenicity of BaP (over a 30-fold increase in females) and NDMA (about a 20-fold increase in males). To estimate the involvement of metabolic enzymes in the alteration of mutagenicity, we measured the activity of ethoxyresorufin-O-deethylase (EROD) and methoxyresorufin-O-demethylase (MROD) (phase I enzymes), and UDP-glucuronosyltransferase (UGT) and glutathione S-transferase (GST) (phase II enzymes) in each S9 sample. The activity of phase I enzymes increased, even at the 3rd day following administration, and then decreased gradually, except in the case of AA, while the activity of phase II enzymes increased slightly. These results suggest that non-genotoxic hepato-hypertrophic compounds may be partly involved in carcinogenesis by modulating the metabolism of pre-carcinogens incorporated from the environment, in a manner that is dependent on sex and pre-incorporated chemicals.
AB - It remains uncertain why non-genotoxic compounds that result in liver hypertrophy cause liver tumors. In an effort to resolve this issue, we examined whether liver postmitochondrial fraction (S9) prepared from rats treated with non-genotoxic compounds affected the genotoxicity of pro-mutagens. Known hepatotoxic compounds, such as piperonyl butoxide (PBO), decabromodiphenyl ether (DBDE), beta-naphthoflavone (BNF), indole-3-carbinol (I3C) and acetaminophen (AA),were orally administered to male and female F344 rats at doses sufficient to cause liver hypertrophy. Rats received diets containing each test compound for 3 days, 4 weeks or 13 weeks, and were then kept for 4 weeks without the test chemical. S9 prepared from the livers of each group was used for the Ames test with 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), benzo[a]pyrene (BaP) and N-nitrosodimethylamine (NDMA). In both sexes, liver hypertrophy was observed following administration of all test compounds, and was then reversed to the control state when administration ceased. The mutagenicity of MeIQx, BaP and NDMA increased with the use of S9 derived from rats treated with non-genotoxic compounds other than AA. DBDE administration had a marked effect on the mutagenicity of BaP (over a 30-fold increase in females) and NDMA (about a 20-fold increase in males). To estimate the involvement of metabolic enzymes in the alteration of mutagenicity, we measured the activity of ethoxyresorufin-O-deethylase (EROD) and methoxyresorufin-O-demethylase (MROD) (phase I enzymes), and UDP-glucuronosyltransferase (UGT) and glutathione S-transferase (GST) (phase II enzymes) in each S9 sample. The activity of phase I enzymes increased, even at the 3rd day following administration, and then decreased gradually, except in the case of AA, while the activity of phase II enzymes increased slightly. These results suggest that non-genotoxic hepato-hypertrophic compounds may be partly involved in carcinogenesis by modulating the metabolism of pre-carcinogens incorporated from the environment, in a manner that is dependent on sex and pre-incorporated chemicals.
KW - Ames test
KW - Liver hypertrophic compound
KW - Metabolism
KW - Mutation
UR - http://www.scopus.com/inward/record.url?scp=84897727342&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84897727342&partnerID=8YFLogxK
U2 - 10.3123/jemsge.2013.011
DO - 10.3123/jemsge.2013.011
M3 - Article
VL - 36
SP - 1
EP - 9
JO - Genes and Environment
JF - Genes and Environment
SN - 1880-7046
IS - 1
ER -