Keisuke Akagi

Inhibition of mammary gland carcinogenesis by green tea catechins and other naturally occurring antioxidants in female Sprague-Dawley rats pretreated with 7,12-dimethylbenz[a]anthracene

Effects of the naturally occurring antioxidants on mammary gland carcinogenesis were examined in female Sprague-Dawley rats pretreated with 7,12-dimethylbenz[alpha]anthracene (DMBA). Groups of 15-16 7-week-old rats received a 50 mg/kg body weight intra-gastric dose of DMBA, and starting one week thereafter placed on diet containing 0.4% catechol, 1.0% gamma-oryzanol, 2.0% phytic acid, 1.0% green tea catechins (GTC), 1.0% tannic acid or basal diet alone for 35 weeks. Although the final incidences and multiplicities of mammary tumors were not significantly different between DMBA-treated groups, the numbers of survivors in the antioxidant-treated groups at the end of the experiment at week 36 were significantly higher than in the basal diet group. In particular, the survival rate of the GTC group at 93.8% strongly contrasted with that of only 33.3% for rats on the basal diet. At the end of week 18, when all the animals were still alive, the average size of palpable mammary tumors was significantly smaller in the catechol, phytic acid and catechins groups. These results indicate that antioxidants, and GTC in particular, inhibit rat mammary gland carcinogenesis after DMBA initiation.

Lack of inhibitory effects of green tea catechins in 1,2-dimetylhydrazine-induced rat intestinal carcinogenesis model: comparison of the different formulations, administration routes and doses

Differences in the modifying effects of green tea catechins (GTC) on intestinal carcinogenesis by different formulations, doses and administration routes were investigated in male rats pretreated with 1,2-dimethylhydrazine (DMH). One hundred and eighty nine F344 male rats received subcutaneous injections of DMH at 40 mg/kg body weight twice a week for 3 weeks. Three days after completion of the carcinogen treatment, they were divided into nine groups. Each was administered a different source of 0.1% or 0.01% of GTC (Mitsui Norin Co. (M) or Taiyo Kagaku Co. (T)) either in the diet (D) or the drinking water (W), or basal diet and tap water alone without GTC for 33 weeks and then killed for autopsy. The survival rate tended to be lower with 0.01% MGTC (W) group than in the other groups. In the large intestine, although the multiplicity and/or incidences of adenomas showed tendencies for dose-dependent decrease in all GTC groups, and the average volumes of tumors tended to be decrease dose-dependently in the MGTC (W) and TGTC (W) groups, the multiplicity of carcinomas did not show such a trend, rather being significantly increased in the 0.01% MGTC (D) and 0.1% TGTC (W) groups. In the small intestine, the incidence and the multiplicity of tumors in all GTC treated groups had a tendency to decrease. On the other hand, the volume of tumors was increased with statistical significance in the 0.01% MGTC (W) and 0.1% TGTC (W) groups. Thus it can be concluded that GTC does not exert chemopreventive effects on intestinal carcinogenesis irrespective of its formulation, dose or route of administration.

Sequential Morphological and Biological Changes in the Glandular Stomach Induced by Oral Administration of Catechol to Male F344 Rats

Histogenesis and mechanisms of catechol-induced rat glandular stomach carcinogenesis were investigated in male F344 rats. Groups of 5 or 6 rats were treated with dietary catechol at doses of 1, 0.5, 0.1, and 0.01% for 12 hr or for 1, 2, 3, or 7 days or at a dose of 0.8% for 1, 2, 4, 12, and 24 wk; rats were then euthanatized. The initial morphological changes were edema of the gastric wall, inflammatory-cell infiltration, erosion in the pyloric region close to the duodenum, and considerable increase in apoptosis at 12 hr; later, changes included augmented DNA synthesis and cell proliferation, as evaluated by bromodeoxyuridine labeling index and thickness of mucosa, respectively, on day 1. Downward hyperplasia due to excess regeneration appeared at edges of ulceration at week 2. This lesion disappeared, and then submucosal hyperplasia appeared in the course of adenoma development. Only slight expression of c-myc or c-fos was apparent after 30-min oral administration or 1-, 3-, and 6-hr oral administration of catechol. No increase in lipid peroxide levels was evident in gastric epithelium fed catechol for 1 wk. The amount of catechol distributed in the glandular stomach and forestomach epithelium, which is not a target for carcinogenesis, did not differ 1, 3, 6, and 24 hr after a single intragastric dose of 75 mg/kg body weight. Amounts of catechol bound to tissue protein were also not specifically high in the glandular stomach. These results indicate that regenerative cell proliferation due to toxicity plays an important role in catechol-induced glandular stomach carcinogenesis. Protein binding and free radicals may not be largely responsible for the toxicity.

Lack of Chemoprevention Effects of the Monoterpene d‐Limonene in a Rat Multi‐organ Carcinogenesis Model

Modifying effects of dietary administration of the monoterpene d‐limonene were examined using a multi‐organ carcinogenesis model. Groups of twenty F344 male rats were treated sequentially with N‐diethylnitrosamine (DEN, i.p.), N‐methyl‐N‐nitrosourea (MNU, i.p.), 1,2‐dimethylhydrazine (DMH, s.c.), N‐butyl‐N‐(4‐hydroxybutyl)nitrosamine (BBN, in drinking water) and dihydroxy‐di‐N‐propylnitrosamine (DHPN, in drinking water) during the first 4 weeks (DMBDD treatment), and then (d‐limonene was administered in the diet, at the dose of 2.0, 1.0 or 0.5%. The maximal tolerable dose was 2.0% under the present conditions. Further groups were treated with DMBDD or 2.0%d‐limonene alone as controls. All surviving animals were killed at week 28, and major organs were examined histopathologically for development of preneoplastic and neoplastic lesions. The incidences and/or multiplicities of renal atypical tubules and adenomas were increased in animals fed 2.0%d‐limonene. The immunohistochemical reactivity for α2u‐globulin in the proximal tubules was greater in rats fed d‐limonene than in the carcinogen alone group. No enhancing or inhibitory effect was noted for tumor development in other organs. The present results indicate a lack of any chemopreventive effect of (d‐limonene in any organ of male rats under the present experimental conditions.

Effect of ethanol on paraquat toxicity in F344 rats

The potential modifying effects of ethanol and paraquat on lesion development in livers and lungs of male F344 rats were studied. Animals were divided into diethylnitrosamine (DEN)-initiated and non-initiated groups, subgroups of each being exposed to 10 ml 20% ethanol/kg body weight, 2.5 or 10 mg paraquat/kg body weight or a combination of 10 ml 20% ethanol/kg body weight and 2.5 or 10 mg paraquat/kg body weight, given by intragastric intubation three times a week. Controls received 10 ml saline/kg body weight. All animals were subjected to two-thirds partial hepatectomy at the end of wk 3 and killed at the end of wk 8. All five rats receiving 10 mg paraquat/kg body weight without DEN-pretreatment died before termination of the experiment, but the additional ethanol treatment saved animals: only one of five rats died. Rats administered 2.5 or 10 mg paraquat/kg body weight demonstrated lung toxicity, as evidenced by fibrosis and hyperplasia, but not when simultaneously treated with ethanol in DEN-pretreated groups. In the liver, however, evaluation of glutathione S-transferase placental form (GST-P)-positive foci did not reveal any influence of the treatments on lesion development in DEN-initiated animals. It is concluded that ethanol decreases paraquat toxicity, and that neither agent, alone or in combination, exerts any hepatocarcinogenic modification potential.