A 13-week subchronic toxicity study of hinokitiol administered in the diet to F344 rats.

Myocarditis has been reported in male F344 rats given a diet containing hinokitiol (HT). A subchronic toxicity study was here performed to re-evaluate toxic effects of HT in both sexes of F344 rats with dietary administration at concentrations of 0%, 0.02%, 0.07% and 0.2% for 13 weeks. Significant reduction of body weight gain was noted in 0.2% males and 0.07% and above females. Significant decrease in RBC counts, hemoglobin and hematocrit was detected in 0.07% and 0.2% females. Significant increase in MCV was observed in 0.07% and above males and 0.2% females. In the rats given 0.07% and 0.2%, significant increase in total protein and albumin were detected in males, and in total cholesterol in females. Significant increases in total cholesterol, urea nitrogen and creatinine were also detected in the 0.2% males. Significant increase in relative liver weights was detected in the 0.07% and above males and females. Absolute and relative heart weights were significantly decreased in the 0.07% and above males. Based on the above findings the no-observed-adverse-effect level (NOAEL) of HT for both male and female rats was estimated to be 0.02%, translating into 12.7 and 14.8 mg/kg b.w./day, respectively. Myocarditis was not evident in the present study.

Ex vivo culturing of stromal cells with dexamethasone-loaded carboxymethylchitosan/poly(amidoamine) dendrimer nanoparticles promotes ectopic bone formation.

Recently, our group has proposed a combinatorial strategy in tissue engineering principles employing carboxymethylchitosan/poly(amidoamine) dendrimer nanoparticles (CMCht/PAMAM) towards the intracellular release and regimented supply of dexamethasone (Dex) aimed at controlling stem cell osteogenic differentiation in the absence of typical osteogenic inducers, in vivo. In this work, we have investigated if the Dex-loaded CMCht/PAMAM dendrimer nanoparticles could play a crucial role in the regulation of osteogenesis, in vivo. Macroporous hydroxyapatite (HA) scaffolds were seeded with rat bone marrow stromal cells (RBMSCs), whose cells were expanded in MEM medium supplemented with 0.01 mg ml(-1) Dex-loaded CMCht/PAMAM dendrimer nanoparticles and implanted subcutaneously on the back of rats for 2 and 4 weeks. HA porous ceramics without RBMSCs and RBMSCs/HA scaffold constructs seeded with cells expanded in the presence and absence of 10(-8) M Dex were used as controls. The effect of initial cell number seeded in the HA scaffolds on the bone-forming ability of the constructs was also investigated. Qualitative and quantitative new bone formation was evaluated in a non-destructive manner using micro-computed tomography analyses of the explants. Haematoxylin and Eosin stained implant sections were also used for the histomorphometrical analysis. Toluidine blue staining was carried out to investigate the synthesis of proteoglycan extracellular matrix. In addition, alkaline phosphatase and osteocalcin levels in the explants were also quantified, since these markers denote osteogenic differentiation. At 4 weeks post-implantation results have shown that the novel Dex-loaded carboxymethylchitosan/poly(amidoamine) dendrimer nanoparticles may be beneficial as an intracellular nanocarrier, supplying Dex in a regimented manner and promoting superior ectopic de novo bone formation.

A 13-week subchronic toxicity study of dietary administered saponin-rich and isoflavones-containing soybean extract in F344 rats.

A subchronic toxicity study of soybean extract was performed in F344 rats with dietary administration at concentrations of 0%, 1.25%, 2.5% and 5% for 13 weeks. No mortality or abnormal clinical signs in any group were observed. Body weight gains were decreased with a tendency for reduction of feed intake in the 1.25% and above female and 5% male groups. In males, absolute and relative liver weights were increased in the 1.25% and above groups. In females relative kidney weights were increased in the 1.25% and above groups. Other significant changes such as decreased RBC and hematocrit and increased urea nitrogen were detected in the 2.5% and/or 5% groups. On histopathological observation, atrophy of the ventral prostate was observed in all animals in the 5% male group. Mucification and atrophy of the vaginal epithelium and increased atretic follicles in ovaries were noted in 2.5% and 5% female rats. Based on the above findings the lowest-observed-adverse-effect level for male and female rats was estimated to be 1.25% (707.2 and 751.8 mg/kg b.w./day, respectively).

Evaluation of toxicity of green tea catechins with 90-day dietary administration to F344 rats.

Green tea catechins (GTC), polyphenols extracted from the stalks and leaves of Camellia sinensis, are found in the different types of tea beverages and as antioxidant additives to many foods, snacks, fats and fatty oils. As a part of their safety assessment, subchronic toxicity was investigated in male and female F344 rats with dietary administration at concentrations of 0 (control), 0.3%, 1.25% and 5.0% for 90 days. The average daily intakes of GTC in each group were 180, 764 and 3525mg/kg body weight/day, respectively for males, and 189, 820 and 3542mg/kg body weight/day, respectively for females. No mortality or obvious clinical signs were observed throughout the experimental period but body weights were reduced from week 1 to the end of the experiment in 5.0% males. In serum biochemistry, alanine transaminase and alkaline phosphatase in 5.0% males and females and aspartate transaminase in 5.0% females were increased, together with the relative liver weights in both sexes receiving 5.0%. Although decreases were evident for total cholesterol in 0.3-5.0% males and triglycerides in 1.25% and 5.0% males and 5.0% females, these changes were not considered to be adverse. Hematology and histopathological observation revealed no GTC-related toxicological changes. Based on above findings, the no observed adverse effect level (NOAEL) of GTC was estimated to be 1.25% (764mg/kg body weight/day for males and 820mg/kg body weight/day for females).

Lack of chemopreventive effects of alpha-eleostearic acid on 7,12-dimethylbenz[a]anthracene (DMBA) and 1,2-dimethylhydrazine (DMH)-induced mammary and colon carcinogenesis in female Sprague-Dawley rats.

alpha-Eleostearic acid is one of the conjugated linolenic acids from tung oil, which is obtained from the seeds of Aleurites fordii. The effects of dietary alpha-eleostearic acid (18:3, n-5) on the post-initiation period of 7,12-dimethylbenz[a]anthracene (DMBA) and 1,2-dimethylhydrazine (DMH)-induced mammary and colon carcinogenesis were examined using female Sprague-Dawley (SD) rats. For initiation, rats were given subcutaneous injections of 40mg/kg body weight (5 times) and 20mg/kg body weight (3 times) of DMH during the age of 6-8 weeks and a single intragastric administration of 50mg/kg body weight of DMBA at 9 weeks. Then, the animals were treated with 0%, 0.01%, 0.1% or 1.0% alpha-eleostearic acid for 34 weeks. Control rats received the basal diet alone or 1.0% alpha-eleostearic acid without prior initiation treatment. All surviving animals were killed at week 37 of the experiment. There were no statistically significant alterations in any of the parameters for either mammary or colon tumors. These results thus indicate that alpha-eleostearic acid does not exert clear modification effects on DMBA and DMH-induced mammary and colon carcinogenesis, at least under the present experimental conditions.

A subchronic toxicity study of dunaliella carotene in F344 rats.

Dunaliella carotene, extracted from dunaliella alga (Dunaliella bardawil or Dunaliella salina), for use as a food-coloring agent, has beta-carotene as its mainly constituent. As there have been no reports of toxicological evaluation, a 90-day subchronic toxicity study was here performed in F344 rats at dose levels of 0 (control), 0.63%, 1.25%, 2.5% and 5% in powdered basal diet. The average daily intakes of dunaliella carotene were 352, 696, 1420 and 2750 mg/kg/day, respectively, for males, and 370, 748, 1444 and 2879 mg/kg/day for females. No mortality or treatment-related clinical signs were observed throughout the experimental period in any of the groups. Body weight gain was slightly but significantly (p < 0.05) reduced from week 5 to the end of the experiment in 2.5% and 5% males. Increased PLT were observed in 1.25% and 5% males, and 2.5% and 5% females. Significant elevations or tendencies for increase in serum T. Cho and Ca were observed in all treated males and females, with clear dose-dependence in males. Organ weight measurement and histopathological observation revealed no toxicological changes. Based on growth suppression, no-observed-adverse-effect-levels (NOAELs) were estimated to be 1.25% (696 mg/kg/day) for males and 5% (2879 mg/kg/day) for females. As increases in serum Ca were observed in the lowest group in both sexes, a no-observed-effect level (NOEL) could not be determined in this study.

Lack of subchronic toxicity of an aqueous extract of Agaricus blazei Murrill in F344 rats.

Agaricus blazei Murrill, an edible mushroom, is widely used as a functional food due to its possible medicinal effects. Aqueous extracts are also used as food additive to provide an agreeable bitter taste. As a part of its safety assessment, the present 90-day subchronic toxicity study was performed in F344 rats. To establish a no-observed-adverse-effect level (NOAEL), rats were fed powder diet containing A. blazei Murrill aqueous extract at dose levels of 0 (basal diet), 0.63, 1.25, 2.5 and 5% (maximum) for 90 days. During the experiment, there were no remarkable changes in general appearance and no deaths occurred in any experimental group. Although serum blood urea nitrogen was slightly but significantly increased in males of the 2.5 and 5% groups, no related histopathological changes were observed in the kidney, and serum creatinine levels were rather reduced, suggesting the increase of blood urea nitrogen to be of little toxicological significance. Hematology, organ weight measurement and histopathological observation revealed no test compound-related toxicological changes. In conclusion, A. blazei Murrill extract even at 5% in the diet (2654 mg/kgb.w./day for male rats and 2965 mg/kgb.w./day for female rats) did not cause remarkable adverse effects in F344 rats. Thus, the NOAEL was concluded to be 5% in the diet.

Sequential analysis of testicular lesions and serum hormone levels in rats treated with a Psoralea corylifolia extract.

In order to clarify pathogenetic targets for the testicular toxicity of a extract of Psoralea corylifolia (P. corylifolia), F344 rats were fed diet containing 3% P. corylifolia extract for up to 12 weeks and subjected to hormone assays and histopathological examination on the testis and epididymis at weeks 1, 2, 4, 8 and 12 (Exp 1). Similar analyses were performed on 1, 3, 7 and 14 days after a single gavage administration of the P. corylifolia extract at a dose of 10 g/kg b.w. (Exp 2). In Exp 1, increase in the numbers of degenerated and exfoliated germ cells and loss of elongated spermatids beyond steps 7 or 8 were initially observed in the seminiferous tubules at week 1, followed by more pronounced degeneration of germ cells with depletion of post-meiotic populations from week 2. The tubular degeneration was associated with Leydig cell atrophy and persistent reduction of serum testosterone and FSH levels throughout the treatment period and a slight reduction of serum LH in later stages. In Exp 2, reduction of serum testosterone and FSH levels preceded degeneration of germ cells in stage VII and VIII tubules at 3 and 7 days after the administration. The results suggest that rapid androgen deprivation reflecting direct interference with Leydig cell function and simultaneous disturbance of the pituitary-testicular axis play pivotal roles in P. corylifolia extract-induced germ cell injury in seminiferous tubules.

A subchronic toxicity study of shea nut color in Wistar rats.

Shea nut color, obtained from nuts of the shea tree (Butyrospermum parkii), is used as a food-coloring agent. Flavonoid pigments are considered to be the responsible constituents. As there have been no reports of toxicological evaluation, a 13-week subchronic toxicity study was performed in Wistar Hannover rats at dose levels of 0 (control), 0.07, 0.31, 1.25 and 5% in powdered basal diet. The average of daily shea nut color intake was 51.3, 226.1, 986.8 and 3775.5 mg/kg/day for males and 56.4, 272.9, 1166.7 and 4387.7 mg/kg/day for females, respectively. During the administration period, daily observation of clinical signs and weekly measurement of body weights and food consumption were performed. After the end of the treatment, hematology, serum biochemistry, organ weight and histopathological examinations were conducted. No significant toxicological changes were observed in any parameters in this study. Hence, the no adverse effect dose of shea nut color was estimated to be greater than 5.0% for both sexes (3775.5 mg/kg/day for males and 4387.7 mg/kg/day for females).

Iron lactate induction of pancreatic and endometrial proliferative lesions and a lack of increased tumors in a 104-week carcinogenicity study in F344 rats.

Iron lactate has been used as a food additive for iron supplementation. The present study was conducted to determine whether it might have carcinogenic potential. A total of 150 male and 150 female Fischer 344 rats were divided into three groups and fed basal diet containing 0, 1 or 2% of iron lactate for 104 weeks. No iron lactate-induced tumors were observed in any groups, although the incidences of pancreatic acinar cell and endometrial gland hyperplasias were increased in males and females, respectively, in the 2% group. Thus our in vivo animal data indicate that iron lactate lacks carcinogenicity in male and female F344 rats. However, estrogenic effects might be concluded based on the data for endometrial lesions. In a second experiment, an estrogen responsive rat pituitary tumor cell line, MtT/Se, and a human breast cancer cell line, MCF-7, were therefore employed to examine the estrogenic potential of iron lactate with regard to receptor binding affinity and ERE-reporter gene activation. Results in both cases were negative. Further investigations are needed to elucidate the mechanisms of induction of pancreatic and endometrial proliferative lesions by iron lactate.

Synergistic effects of high-dose soybean intake with iodine deficiency, but not sulfadimethoxine or phenobarbital, on rat thyroid proliferation.

The specificity and dose dependence of the synergistic effects of soybean intake with iodine deficiency on the induction of thyroid proliferation were investigated in female F344 rats. In the first experiment, rats were divided into 6 groups, each consisting of 5 animals, and fed a basal diet containing 20% gluten, an iodine-deficient basal diet alone or an iodine-deficient diet containing 0.2%, 1.0%, 5.0% or 25% defatted soybean for 5 weeks. Soybean feeding synergistically induced thyroid hyperplasias with iodine deficiency only at the 25% dose. In the second experiment, rats were also divided into 6 groups, each consisting of 5 animals, and fed a basal diet, a diet containing 20% defatted soybean, 0.025% sulfadimethoxine (SDM), 20% defatted soybean + 0.025% SDM, 0.05% phenobarbital (PB) or 20% defatted soybean + 0.05% PB for 5 weeks. The SDM treatments significantly (P < 0.05 - 0.01) increased the thyroid weights, but this increase rate was less prominent in the SDM + soybean group than in the SDM alone group. The PB treatment was also associated with a tendency for increase in thyroid weight, but again this was smaller in the PB + soybean group than in the PB alone group. Although the SDM or PB treatments reduced the serum triiodothyronine and thyroxine levels and consequently increased the serum thyroid-stimulating hormone (TSH) levels, the soybean feeding did not affect or rather attenuated these changes. Our results clearly indicate that soybean feeding does not synergistically enhance the effects of SDM or PB on the rat thyroid. Thus it can be concluded that soybean intake specifically interacts with iodine deficiency in induction of thyroid proliferative lesions in rats, only at high doses.

Site-dependent modulating effects of conjugated fatty acids from safflower oil in a rat two-stage carcinogenesis model in female Sprague-Dawley rats.

Modifying effects of dietary administration of conjugated fatty acids from safflower oil (CFA-S), rich in conjugated linoleic acid, on major organs were examined in the post-initiation stage of a two-stage carcinogenesis model in female rats. Groups of 21 or 22 F344 female rats were treated sequentially with 2,2'-dihydroxy-di-n-propylnitosamine (intragastrically, i.g.), 7,12-dimethylbenz[a]anthracene (i.g.), 1,2-dimethylhydrazine (subcutaneously) and N-butyl-N-(4-hydroxybutyl)nitrosamine (in drinking water) during the first 3 weeks for initiation, and then administered diet containing 1 or 0.1% CFA-S for 33 weeks. Further groups of animals were treated with carcinogens or 1% CFA-S alone, or maintained as non-treated controls. All surviving animals were killed at week 36, and major organs were examined histopathologically for development of pre-neoplastic and neoplastic lesions. The 1 and 0.1% CFA-S treatment significantly decreased the incidence and multiplicity of mammary carcinomas, though a clear dose response was not observed. In the urinary bladder, the incidence of papillary or nodular hyperplasia but not tumors was significantly increased in the 1% CFA-S-treated group. The results indicate that low dose CFA-S may find application as a potent chemopreventor of mammary carcinogenesis.

Green tea catechins enhance tumor development in the colon without effects in the lung or thyroid after pretreatment with 1,2-Dimethylhydrazine or 2,2'-dihydroxy-di-n-propylnitrosamine in male F344 rats.

Modifying effects of green tea catechins (GTCs) on the post-initiation stage of colon, lung and thyroid carcinogenesis were examined in F344 male rats. Groups of 20 animals were given subcutaneous injections of 40 mg/kg body wt of 1,2-dimethylhydrazine twice a week for 2 weeks or oral administration of 0.1% 2,2'-dihydroxy-di-n-propylnitrosamine (DHPN) in the drinking water for 2 weeks for initiation. They then received diet containing 1 or 0.1% green tea catechin or basal diet alone for 33 weeks. Histopathological examination after final sacrifice showed that although total incidence and multiplicity of colon tumors were not significantly different from controls, values for colon adenomas were decreased while those for carcinomas and the average size of tumors were significantly increased in the 0.1% GTC group. A similar tendency was observed for the 1% GTC group. Incidences and/or multiplicity of lung hyperplasia and tumors, and thyroid lesions did not significantly vary among the DHPN-treated groups. These results indicate that GTCs do not inhibit, but rather may enhance colon carcinogenesis, while not influencing lung and thyroid carcinogenesis under the present experimental conditions.

[Clinical utility and safety of diagnostic thoracoscopy].

The increasing use of thoracoscopy performed under local anesthesia has made contributions to the diagnosis of pleural disease with effusion. During the past 7 years, we have performed 100 such thoracoscopy procedures using a flexible fiberoptic bronchoscope. On the basis of our clinical findings, we are able to discuss the utility and safety of this procedure. The causes of pleural effusion were carcinomatous pleurisy in 72 cases, tuberculosis pleurisy in 15 cases, infection without tuberculosis in 4 cases, malignant pleural mesothelioma in 8 cases and one case of asbestosis. The success rate of thoracoscopic pleural biopsies were 97% for carcinomatous pleurisy, 100% for malignant pleural mesothelioma and 86% for tuberculosis pleurisy. This procedure was performed with no serious effect on blood pressure, oxygen saturation, monitored ECG or BGA data, and with no serious complications. Therefore, we concluded that this method is very useful for the diagnosis of pleural effusions and has few complications.

Inhibitory effects of protocatechuic acid on the post-initiation phase of hamster pancreatic carcinogenesis induced by N-nitrosobis(2-oxopropyl)amine.

The chemopreventive effects of protocatechuic acid (PCA) were investigated during the post-initiation stage of the N-nitrosobis(2-oxopropyl)amine (BOP)-initiated hamster pancreatic tumorigenesis model. Female 5-week-old hamsters were divided into 6 groups. Animals in groups 1-3, each consisting of 30 hamsters, were given two s.c. injections of 20 mg/kg body weight of BOP with a one week interval as an initiation treatment. After the BOP injection, hamsters in groups 1 and 2 were respectively fed diet supplemented with 1000 or 500 ppm of PCA for 49 weeks. The animals in group 3 were treated with BOP alone. The animals in groups 4-6, each consisting of 10 hamsters, were given 1000 or 500 ppm PCA, or basal diet alone without prior BOP injection. At the termination of experimental week 52, the incidences and multiplicities of neoplastic lesions in the pancreas were comparable among the BOP-treated groups. However, the incidence of pancreatic tumors larger than 3 cm was significantly lower in the PCA-treated high dose groups than in the control group (p < 0.05). Moreover the incidence of advanced pancreatic cancers which had directly invaded adjacent tissues such as the diaphragm, spleen and stomach was reduced by the PCA treatments, being significantly (p < 0.01) lower in group 2 than in group 3. Our results thus indicated that PCA can inhibit the late post-initiation or progression phase of BOP-induced pancreatic carcinogenesis in hamsters.

Enhancing effects of Thai edible plants on 2-amino-3, 8-dimethylimidazo(4,5-f)quinoxaline-hepatocarcinogenesis in a rat medium-term bioassay.

Boesenbergia pandurata (Zingiberaceae), Languas galanga (Zingiberaceae) and Citrus hystrix (Rutaceae) are edible plants that are commonly used as flavors or condiments in various Thai food dishes. They are known to exert strong anti-promoting activity in a test of tumor promoter-induced Epstein-Barr virus (EBV) activation. In the present study their effects on hepatocarcinogenesis were investigated in a medium-term bioassay using F344 male rats. C. hystrix significantly enhanced 2-amino-3,8-dimethylimidazo(4, 5-f)quinoxaline-associated preneoplastic liver cell focus development while B. pandurata and L. galanga had borderline effects. The results suggest that C. hystrix as well as B. pandurata and L. galanga may contain agents augmenting the hepatocarcinogenicity of 2-amino-3,8-dimethylimidazo(4,5-f)quinoxaline.

Binding of a large chondroitin sulfate/dermatan sulfate proteoglycan, versican, to L-selectin, P-selectin, and CD44.

Here we show that a large chondroitin sulfate proteoglycan, versican, derived from a renal adenocarcinoma cell line ACHN, binds L-selectin, P-selectin, and CD44. The binding was mediated by the interaction of the chondroitin sulfate (CS) chain of versican with the carbohydrate-binding domain of L- and P-selectin and CD44. The binding of versican to L- and P-selectin was inhibited by CS B, CS E, and heparan sulfate (HS) but not by any other glycosaminoglycans tested. On the other hand, the binding to CD44 was inhibited by hyaluronic acid, chondroitin (CH), CS A, CS B, CS C, CS D, and CS E but not by HS or keratan sulfate. A cross-blocking study indicated that L- and P-selectin recognize close or overlapping sites on versican, whereas CD44 recognizes separate sites. We also show that soluble L- and P-selectin directly bind to immobilized CS B, CS E, and HS and that soluble CD44 directly binds to immobilized hyaluronic acid, CH, and all the CS chains examined. Consistent with these results, structural analysis showed that versican is modified with at least CS B and CS C. Thus, proteoglycans sufficiently modified with the appropriate glycosaminoglycans should be able to bind L-selectin, P-selectin, and/or CD44.

Studies on the carcinogenicity of potassium iodide in F344 rats.

A chronic toxicity and carcinogenicity study, in which male and female F344/DuCrj rats were given potassium iodide (KI) in the drinking water at concentrations of 0, 10, 100 or 1000 ppm for 104 weeks, and a two-stage carcinogenicity study of application at 0 or 1000 ppm for 83 weeks following a single injection of N-bis(2-hydroxypropyl)nitrosamine (DHPN), were conducted. In the former, squamous cell carcinomas were induced in the salivary glands of the 1000 ppm group, but no tumors were observed in the thyroid. In the two-stage carcinogenicity study, thyroidal weights and the incidence of thyroid tumors derived from the follicular epithelium were significantly increased in the DHPN+KI as compared with the DHPN alone group. The results of our studies suggest that excess KI has a thyroid tumor-promoting effect, but KI per se does not induce thyroid tumors in rats. In the salivary gland, KI was suggested to have carcinogenic potential via an epigenetic mechanism, only active at a high dose.

Usefulness of serum carboxy-terminal telopeptide of type I collagen (ICTP) as a marker of bone metastasis from lung cancer.

BACKGROUND: Serum pyridinoline cross-linked carboxy-terminal telopeptide of type I collagen (ICTP) is a metabolite of type I collagen comprising 90% or more of organic substances in bone. Its usefulness as a marker of bone metastasis from malignant tumors is expected. METHOD: We measured ICTP to evaluate its clinical usefulness for diagnosis of bone metastasis in 140 patients with lung cancer. For comparison, serum carcinoembryonic antigen (CEA), cytokeratin 19 fragment (CYFRA 21-1), gastrin-releasing peptide precursor (ProGRP), alkaline phosphatase and calcium were simultaneously measured. ICTP was measured by double-antibody radioimmunoassay. RESULTS: ICTP was significantly higher in patients with bone metastasis from lung cancer than in the group without bone metastasis, patients with other pulmonary diseases or healthy control subjects and showed excellent sensitivity and specificity, indicating that this marker is highly useful for complementary diagnosis of bone metastasis from lung cancer. Moreover, the survival duration was significantly shorter in the ICTP-positive group than in the ICTP-negative group, suggesting that ICTP can be a prognostic factor in lung cancer. CONCLUSION: It is suggested that measurement of ICTP is worthwhile as a serological diagnostic method of bone metastasis from lung cancer. Moreover, since repeated measurements are possible, this measure was considered very helpful in complementary diagnosis of bone metastasis and also as a standard to determine the timing of examinations such as bone scintigraphy.

Effects of arctiin on PhIP-induced mammary, colon and pancreatic carcinogenesis in female Sprague-Dawley rats and MeIQx-induced hepatocarcinogenesis in male F344 rats.

Chemopreventive effects of arctiin, a lignan isolated from Arctium lappa (burdock) seeds, on the initiation or post initiation period of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) induced mammary carcinogenesis in female rats and on 2-amino-3, 8-dimethylimidazo[4,5-f]quinoxaline (MeIQx)-associated hepatocarcinogenesis in male rats were examined. In experiment 1, female Sprague-Dawley (SD) rats were given intragastric doses of 100 mg/kg body wt of PhIP once a week for 8 weeks as initiation. Groups of 20 rats each were treated with 0.2 or 0.02% arctiin during or after PhIP initiation. Control rats were fed 0.2 or 0.02% arctiin, or basal diet alone during the experimental period. Animals were killed at the end of week 48. Although the incidence of mammary carcinomas did not significantly differ among the PhIP-treated groups, multiplicity was significantly decreased in rats given 0.2 (0.7+/-0.7, P<0.05) or 0.02% (1.0+/-1.1, P<0.05) arctiin after PhIP initiation as compared with the PhIP alone controls (2.1+/-2.5). The average number of colon aberrant crypt foci was also significantly decreased in these two groups. Pancreas acidophilic foci were induced in PhIP treated animals with slight decrease in the multiplicity with arctiin during the initiation phase. For liver carcinogenesis, groups of 15 male F344 rats were given a single intraperitoneal injection of diethylnitrosamine (DEN) and starting 2 weeks later, they were administered 0.03% MeIQx in the diet, MeIQx together with 0.5% arctiin, 0.1% arctiin or basal diet for 6 weeks. They were subjected to two-third partial hepatectomy 3 weeks after DEN initiation and killed at the end of week 8 for glutathione S-transferase placental form (GST-P) immunohistochemistry. The numbers and areas of preneoplastic GST-P positive foci were elevated by the treatment with MeIQx, and further increased by the simultaneous treatment with arctiin. These results indicate that arctiin has a protective effect on PhIP-induced carcinogenesis particularly in the mammary gland in the promotion period. On the other hand, it may have a weak co-carcinogenic influence on MeIQx-induced hepatocarcinogenesis. In addition, the results suggested that PhIP is a weak pancreatic carcinogen in female SD rats, targeting acinar cells.