Immunohistochemical demonstration of carcinogen-DNA adducts in target and non-target tissues of rats given a prostate carcinogen, 3,2'-dimethyl-4-aminobiphenyl

An immunohistochemical procedure was applied which allows accurate localization of DNA lesions within organs and tissues of rats given 3,2'-dimethyl-4-aminobiphenyl (DMAB) using polyclonal antibodies against DMAB-DNA adducts. Dose-related nuclear staining was observed in organs regardless of DMAB-carcinogenic organotropism. In the male accessory sex organs, the lateral lobe of the prostate, a non-target site, demonstrated a similar staining intensity to that found for the ventral prostate and seminal vesicle, target sites. Orchiectomy and pretreatment with ethinyl estradiol resulted in a moderate to slight decrease in binding in the accessory sex organs. No observable decrease in staining intensity was evident in most organs 168 h after the administration of DMAB. These findings suggest that DNA adduct formation itself is not necessarily sufficient for tumor induction.

Selective induction of prostate carcinomas in F344 rats treated with intraperitoneal injections of N-hydroxy-3,2'-dimethyl-4-aminobiphenyl

Groups of F344 and Wistar rats were given an intraperitoneal injection of N-hydroxy-3,2'-dimethyl-4-aminobiphenyl (N-OH-DMAB) at a dose of 5 mg/kg body weight with a 1-week dietary pretreatment with ethinyl estradiol (EE), and this regimen was repeated 10 times at one-week intervals. Additional groups were given N-OH-DMAB 10 times without the dietary EE pretreatment. The total experimental period was 60 weeks. Carcinomas and atypical hyperplasias of the prostate developed in 8 (42%) and 16 (84%) of 19 F344 rats without the dietary EE treatment and in 1 (6%) and 7 (39%) of 18 rats with the EE diet, respectively. No prostatic tumors were found in Wistar rats, although atypical hyperplasias were observed in 6 of 18 rats with and 4 of 8 rats without the EE supplementation. Tumor yields in other organs were extremely low, resulting in good survival of the animals. A comparison of the results with those obtained for DMAB suggests that intraperitoneal administration of N-OH-DMAB in F344 provides a better induction method for models of prostate carcinogenesis.

Early proliferative responses of forestomach and glandular stomach of rats treated with five different phenolic antioxidants

The effects of 8 weeks of oral administration of five different phenolic antioxidants, e.g. catechol (CC), resorcinol, hydroquinone (HQ), 2-tert-butyl-4-methylphenol (TBMP) and propylparabene (PP), on forestomach and glandular stomach epithelium of male F344 rats were evaluated using a combined immunohistochemical and histopathological approach. Treatment with CC and TBMP induced a significant elevation of DNA synthesis in the forestomach epithelium, associated with hyperplasia. CC administration also brought about an increase of DNA synthesis in the pyloric gland mucosa, cell proliferation in this case being reflected by an increment in the crypt height. In addition to causing an increase in the pepsinogen-isozyme-1-altered pyloric glands (PAPG), which are considered to be putative preneoplastic precursor lesions in the rat glandular stomach, CC treatment was associated with submucosal growth of pyloric mucosal cells tending to decreased pepsinogen isoenzyme 1 binding. However, DNA synthesis values in these latter areas were lower than in pyloric glands of the control group. In contrast, other phenolic compounds, resorcinol, HQ and PP, did not induce any changes in the stomach mucosa. The present results demonstrated strong proliferative responses in the stomach epithelium for CC and TBMP, indicative of promoting potential in both cases, and suggest that CC and TBMP may exert detrimental effects leading to promotion of stomach carcinogenesis or cancer development via an early proliferative response.

Stomach carcinogenicity of caffeic acid, sesamol and catechol in rats and mice

The carcinogenic potential of caffeic acid, sesamol and catechol was examined in male and female F344 rats and B6C3F1 mice, groups of 30 animals being treated with diets containing 2% caffeic acid, 2% sesamol or 0.8% catechol for 104 weeks (rats) or 96 weeks (mice). Histological examination revealed that caffeic acid induced forestomach squamous cell carcinoma in 57% (P less than 0.001 vs. controls) and 50% (P less than 0.001) of male and female rats, respectively, whereas sesamol was associated with squamous cell carcinoma at incidences of 31% (P less than 0.001) in male rats, and 38% (P less than 0.001) and 17% (P less than 0.05) in male and female mice, respectively. Catechol induced glandular stomach adenocarcinomas in 54% (P less than 0.001) and 43% (P less than 0.001) of male and female rats, respectively. The results thus clearly demonstrated that all three antioxidants are carcinogenic in rodent stomach epithelia.

Modulation of c-myc expression by transforming growth factor beta 1 in human hepatoma cell lines

The effects of transforming growth factor beta 1 (TGF-beta 1) on cell proliferation of human hepatoma cell lines, PLC/PRF/5 and Mahlavu, were investigated under serum-free conditions. DNA synthesis was strongly inhibited in the PLC/PRF/5 cells by addition of TGF-beta 1 (0.5 to 4.0 ng/ml), but remained unchanged in the Mahlavu cells. Also the expression of c-myc mRNA was suppressed by the addition of TGF-beta 1 in the PLC/PRF/5 cells but not in the Mahlavu cells. These results indicate that TGF-beta 1 might regulate cell growth, in part, by modulating c-myc expression, although there is no direct proof that c-myc expression is really relevant to DNA synthesis mediated by TGF-beta 1.

Relationship between lectin binding properties and the expression of blood group ABH antigens in vascular endothelia and red blood cells from 18 primate species

The reactivity was examined of horseradish peroxidase labelled Ulex europaeus agglutinin-I (UEA-I) and Griffonia simplicifolia agglutinin I-B4 (GSAI-B4) with red blood cells and vascular endothelium in formalin-fixed, paraffin embedded tissues from 18 primate species. The expression of blood group ABH antigens in these cells as well as secretions from other tissues was also examined by the indirect immunoperoxidase method using monoclonal anti-ABH antibodies as primary antibodies. In Prosimians and New World monkeys which lack ABH antigens on both red blood cells and endothelial cells, but produce these antigens in other tissue secretions, GSAI-B4 always reacted with both red blood cells and endothelial cells. In Old World monkeys, which express blood group antigens on endothelial cells but not on red blood cells, neither GSAI-B4 nor UEA-I reactivity were observed, except the endothelial cells from blood group B or O individuals occasionally reacted with GSAI-B4 or UEA-I, respectively. Although UEA-I reactivity was not observed in the endothelial cells of gibbon, it reacted with these cells from chimpanzees. In these two anthropoid apes, both endothelial cells and red blood cells expressed ABH antigens as in humans. These results suggest the close evolutionary relationship between the expression of blood group ABH antigens and lectin binding properties of red blood cells and endothelial cells in primate species.

Modulatory interaction between initial clofibrate treatment and subsequent administration of 2-acetylaminofluorene or sodium phenobarbital on glutathione S-transferase positive lesion development

The effects of 2-acetylaminofluorene (2-AFF) or sodium phenobarbital (PB) treatment subsequent to clofibrate (CF) administration in terms of preneoplastic lesion development and induction of hepatocellular carcinomas (HCC) were studied using Fischer 344 rats. Animals received CF (0.3% in diet) for the initial 30 weeks, and then either 2-AAF (0.01% in diet), PB (0.05% in diet) or basal diet until week 78. Further groups were initially given basal diet, and then treated with 2-AAF or PB week 30. Two-thirds partial hepatectomy was carried out on all animals at week 3, sacrifice of representative groups being performed at weeks 30, 48 and 78. No glutathione S-transferase placental form positive (GST-P+) or negative focal or nodular lesions were apparent at the cessation of CF administration. The induction of GST-P+ focal lesions by 2-AAF was markedly decreased at week 48 in the group previously given CF (P less than 0.05) and furthermore, the respective incidences of HCC at week 78 were 4/17 (23.5%) in the CF----2-AAF group and 7/17 (41.2%) in the 2-AAF alone case. No significant differences between CF----PB and PB alone groups were evident with regard to either GST-P+ lesions and HCC at weeks 48 and 78. No CF-specific GST-P negative neoplastic nodules or HCC were observed in any of the experimental groups. These results suggest that pretreatment with CF may inhibit the induction of GST-P+ focal lesions and HCC by subsequently administrated 2-AAF and that CF demonstrates no initiating activity for liver carcinogenesis under the present condition.

Regression of butylated hydroxyanisole (BHA)-induced hyperplasia but not dysplasia in the forestomach of hamsters

The reversibility of butylated hydroxyanisole (BHA)-induced hamster forestomach hyperplasia was examined histopathologically. Groups of 10-15 male Syrian golden hamsters were treated with 2% BHA, for 12, 24 or 48 weeks and in each case then placed on basal diet until termination of the experiment at week 72, or treated with 2% BHA continuously for 72 weeks. Although sequential sampling revealed that BHA-induced hyperplasia reverted after cessation of antioxidant treatment, dysplastic lesions such as squamous cell dysplasia and basal cell dysplasia persisted and tended to increase with time on BHA. Basal cell dysplasia was observed in some hamsters later than squamous cell dysplasia, i.e. those treated with BHA for 24 weeks or more and killed up to 48 weeks later. Whereas the increase in labeling index evident in areas of hyperplasia during treatment returned to control level after cessation, this was not the case for the dysplastic lesions which continued to demonstrate elevated proliferation. The results thus suggest that basal cell dysplasia, including regions of squamous cell dysplasia, may be of particular importance as a precursor pre-neoplastic lesion.

Lack of hepatotoxicity or promotion of enzyme-altered liver foci development in rats treated with harman or norharman

The modifying effects of harman or norharman on liver carcinogenesis were investigated in male F344/DuCrj rats initially treated with N-nitrosodiethylamine (DEN). Two weeks after a single dose of DEN (200 mg/kg, intraperitoneally), rats were given harman or norharman at dietary levels of 1000 and 200 parts per million (ppm), or sodium phenobarbital (PB) at 500 ppm as a positive control, for 6 wk. At wk 3 following DEN administration, all animals were subjected to partial hepatectomy. Marked retardation of body weight gain was observed in rats treated with harman or norharman at 1000 ppm, but not at 200 ppm. Increased relative kidney but not liver weights were associated with harman or norharman treatment, especially in the higher dose groups. Although no toxicity-related hepatocyte lesions were found, severe renal toxic tubular lesions and regeneration were evident. Neither harman nor norharman significantly increased the numbers or areas of glutathione S-transferase placental form (GST-P) positive foci observed after DEN initiation, in clear contrast to PB. The results thus demonstrated that harman and norharman are nontoxic for the liver and lack modifying potential for liver carcinogenesis in our medium-term bioassay system.

Comparative sequential changes in serum and biliary levels of bile acid components after a single dose of D-galactosamine or partial hepatectomy in the rat

In order to characterize changes in bile acid profile during liver cell damage and regeneration, levels of bile acids in serum and bile were determined by high performance liquid chromatography (HPLC) in F344 rats treated with a single dose of D-galactosamine (galactosamine, 300 mg/kg, i.p.) or subjected to two-thirds partial hepatectomy (PH). In the serum, galactosamine caused elevation of conjugated bile acids such as taurocholic acid (TCA) and tauro-beta-muricholic acid (T beta MCA) at the 24 and 48-h time points, whereas unconjugated bile acids including cholic acid (CA) at 24 h and hyodeoxycholic acid (HDCA) at 48 h were increased after PH. In the bile, elevation of TCA showed most remarkable elevation at the 24-h time point in the galactosamine-treated group. All components of biliary bile acids showed rapid decreases from 24 to 48 h. The results demonstrated that while liver tissue damaged by galactosamine is able to conjugate bile acids it allows leakage into the blood stream. In contrast, the results for rats subjected to PH indicated that liver cells during DNA synthesis are not capable of conjugating all free bile acids with taurine although a similar leakage occurs. It is concluded that obvious elevation of serum TCA or CA and biliary T beta MCA could be a useful indicator of hepatocellular proliferation.

DNA-adduct formation in the forestomach of rats treated with 3-tert-butyl-4-hydroxyanisole and its metabolites as assessed by an enzymatic 32P-postlabeling method

Formation of DNA-adducts by 3-BHA or its metabolites, i.e., tert-butyl-1,4-benzoquinone (TBQ) and 5-methoxy-3-tert-butyl-1,2-benzoquinone (3-TBOQ), as well as DNA-adduct formation by 4-nitroquinoline-N-oxide (4NQO), in rat forestomach were examined by an enzymatic 32P-postlabeling assay. Four DNA-adducts were clearly detected in the forestomach after treatment of rats with 4NQO. The sensitivity was 1.9 certain adducts per 10(8) normal nucleotides. On the contrary, no DNA adducts were detected in the forestomach of rats given either a single or repeated oral administration (5 days) of 3-BHA, TBQ or 3-TBOQ. The analyses were carried out under conditions which could detect the DNA-adducts produced by reaction of TBQ with calf thymus DNA in vitro. The results suggest that formation of aromatic adducts in vivo by 3-BHA, TBQ or 3-TBOQ in the rat forestomach-DNA is not evident or at least below the detection limits of the current bioassay.

Modifying effects of simultaneous treatment with butylated hydroxyanisole (BHA) on rat tumor induction by 3,2'-dimethyl-4-aminobiphenyl, 2,2'-dihydroxy-di-n-propylnitrosamine and N-methylnitrosourea

The modifying effects of concurrent treatment with high or low doses of butylated hydroxyanisole (BHA) on wide-spectrum carcinogen-induced carcinogenesis were studied in male F344 rats. Groups of 20 animals were treated with 2 or 0.04% BHA for 24 weeks. Starting 2 weeks after the commencement of BHA treatment, they were given s.c. injection of 50 mg/kg body weight 3,2'-dimethyl-4-aminobiphenyl (DMAB) once a week, i.g. administrations of 200 mg/kg body weight 2,2'-dihydroxy-di-n-propylnitrosamine (DHPN) once every 2 weeks, or i.p. injection of 15 mg/kg body weight N-methylnitrosourea (MNU) once every 2 weeks for 22 weeks. Further groups of rats were treated with DMAB, DHPN, MNU, or 2 or 0.04% BHA alone. All surviving animals were killed 24 weeks after the beginning of the experiment and the target organs examined histopathologically. The BHA treatment dose-dependently decreased the incidence of DMAB-induced liver preneoplastic lesions but was associated with significant tumor induction in the forestomach (papillomas, 40%, P less than 0.01) and urinary bladder (papillomas, 53%, P less than 0.001; carcinomas, 80%, P less than 0.001), where no lesions were observed in the group given only DMAB. Concurrent administration of 2% BHA also significantly inhibited the development of alveolar hyperplasia (P less than 0.001) of the lung in DHPN-treated animals, while enhancing induction of forestomach papillomas (P less than 0.05) and simple hyperplasia in the urinary bladder. Neither MNU nor 2% BHA alone induced forestomach carcinoma or papillary or nodular hyperplasia (PN hyperplasia) in the urinary bladder. However, these lesions were observed in 100% (P less than 0.001) and 55% (P less than 0.001) of animals respectively, receiving the two compounds in combination. These results demonstrated that concurrent treatment with BHA not only inhibits but can also strongly enhance carcinogenesis depending on the organ, irrespective of whether the carcinogens act directly or require metabolism. The finding that BHA potently modified carcinogenesis at 0.04% in diet, 1/50 of the carcinogenic dose, suggests that actual dietary levels close to the human situation might play a significant role in tumor development in man.

Antagonistic effect of diethylmaleate on the promotion of forestomach carcinogenesis by butylated hydroxyanisole (BHA) in rats pretreated with N-methyl-N'-nitro-N-nitrosoguanidine

The effects of diethylmaleate (DEM), previously demonstrated to inhibit butylated hydroxyanisole (BHA)-induced forestomach hyperplasia, on BHA promotion of forestomach carcinogenesis in rats pretreated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were examined. Groups of male 6-week-old F344 animals were given a single i.g. administration of 150 mg/kg body weight MNNG and starting 1 week later administered powdered diet containing 1% BHA plus 0.2% DEM, 1% BHA, 0.2% DEM or basal diet alone for 51 weeks. Further groups of rats were treated with 1% BHA plus 0.2% DEM, 1% BHA, 0.2% DEM or basal diet alone without MNNG pretreatment. Histopathological assessment of lesions at week 52 revealed enhancement of MNNG-initiated papilloma (100 versus 50%) and squamous cell carcinoma (100 versus 0%) development by BHA as compared to controls. Additional treatment with DEM, however, significantly reduced the relative incidences of carcinoma in situ (0 versus 35.7%) and squamous cell carcinoma (35.7 versus 100%), as well as BHA-induced forestomach hyperplasia with or without prior MNNG treatment. The results thus clearly demonstrate that DEM acts as a potent antagonist to BHA-promotion of rat forestomach carcinogenesis.

[Dental caries of primary teeth and life habits in Shinshinotsu Nursery School: three years of observations]

It is well known that there is a high positive correlation between increases in caries increment and life habits such as use of nursing bottle, tooth brushing, between-meal eating, and sweet consumption. The purpose of this study was to analyze data of caries status in primary dentition and life habits observed in 373 Shinshinotsu nursery schoolchildren aged 3-5 years over three years. Dental examinations were conducted in good natural light using dental mirror and probe. Caries was diagnosed according to the Welfare Ministry criteria and life habits were examined by a questionnaire. The mean number of df was 7.1 for the whole sample for three years and 17.6 of the children were caries free, whereas 47.3 were more than 10 df. The former group showed the best score for the frequency of between-meal eating, frequency of sweet consumption, tooth brushing habits, and frequency of fluoride application. The latter group showed a tendency to lower sweet consumption during the three years. Our data also showed that the life habits at nursing (use of nursing bottle and weaning period) influenced incidence of caries.

Placental form of glutathione S-transferase in normal and diseased human uterine cervical mucosa

Expression of the human placental form of glutathione S-transferase (GST-pi), an enzyme proposed as a marker for human and experimental neoplasia, was immunohistochemically evaluated in 51 samples of 'normal' and diseased adult human uterine cervix. Five fetal uteri were also studied. GST-pi positivity was detected in 54, 92, 95 and 83% of the 'normal', non-neoplastic, cervical intra-epithelial neoplasia (CIN) and cancer cases respectively. All five fetal uteri and the positive 'normal' adult cases presented cells immunostained for GST-pi throughout the thickness of the mucosa, including the basal layer. Some non-neoplastic conditions like inflammation, repair and metaplasia and some dysplastic and neoplastic lesions showed areas of positively stained cells within an otherwise negative tissue, indicating a phenotypic heterogeneity regarding the enzyme expression. Our results confirm that GST-pi has a fetal character and indicate that it may appear in the adult cervical squamous epithelia under 'normal' or pathological conditions not necessarily linked to the process of carcinogenesis. Therefore it cannot be used as a marker for cervical epithelial neoplasia.

Modulation of diethylnitrosamine-initiated placental glutathione S-transferase positive preneoplastic and neoplastic lesions by clofibrate, a hepatic peroxisome proliferator

The effect of clofibrate (CF) on proliferation of diethylnitrosamine (DEN)-initiated glutathione S-transferase placental form (GST-P)-positive preneoplastic and neoplastic lesions as studied in male F344 rats. Animals were given a single i.p. injection of 200 mg/kg body weight of DEN, and then from 2 weeks later were given a diet containing 0.3% CF (group 1), or no supplement (group 2) until week 64. Group 3 received an injection of 0.9% NaCl instead of DEN and then a diet containing 0.3% CF, like group 1. Animals in all groups were subjected to partial hepatectomy at week 3 and killed at weeks 8, 20, 32, 49 or 64. The results showed that development of GST-P-positive lesions was significantly less in group 1 than in group 2 from week 8 (P less than 0.05). However, in group 1, morphologically distinguishable GST-P-negative preneoplastic lesions increased from week 20 (P less than 0.05), and the total number of GST-P-positive and -negative lesions was significantly greater than that in group 2 from week 32 (P less than 0.05). The induction of hepatocellular carcinoma (HCC) was greater in group 1 than in group 2 from week 49. All the HCCs induced in group 2 were GST-P-positive, whereas 38.9% (7/18) of those in group 1 were GST-P-negative. In group 3, only a few GST-P-positive and/or -negative preneoplastic lesions developed by week 64. These results suggest that CF has tumor-promoting activity, and that GST-P-positive cells induced by DEN changed to GST-P-negative cells on subsequent treatment with CF.

Amino acid residues stabilizing a Bacillus alpha-amylase against irreversible thermoinactivation

The alpha-amylase of Bacillus licheniformis (BLA) is stable and active at high temperature. More than 80% of its activity is retained after heat treatment at 90 degrees C for 30 min, and the optimum temperature for its activity is 80-85 degrees C. In contrast, the alpha-amylase of Bacillus amyloliquefaciens (BAA), the amino acid sequence of which shows 80% homology with that of BLA, is rapidly inactivated at 90 degrees C. Various chimeric genes were constructed from the structural genes for the two enzymes, and their products were analyzed for stability as to irreversible thermoinactivation. Two regions in the amino acid sequence of BLA comprising Gln178 (region I) and the 255th-270th residues (region II), respectively, were shown to determine the thermostability of BLA. Region I plays a major role in determining the thermostability. By means of site-directed mutagenesis of the BAA gene, deletion of Arg176 and Gly177 in region I and substitutions of alanine for Lys269 and aspartic acid for Asn266 in region II were shown to be responsible for the enhancement of the thermostability. Mutant BAAs containing the above deletion and substitutions showed almost the same thermostability as BLA as to irreversible thermoinactivation. Nevertheless, the mutant BAAs showed a temperature optimum as low as that of BAA (65 degrees C), indicating that they are still susceptible to reversible inactivation at temperatures higher than 65 degrees C.

The relative value of glycated albumin, hemoglobin A1c and fructosamine when screening for diabetes mellitus

We compared the usefulness of three glycated serum proteins, glycated albumin (GA), glycated hemoglobin (HBA1c) and fructosamine (FA), for diabetic screening purposes. We measured these indices in 302 adults, most of whom underwent yearly physical examinations. We measured GA and HbA1c with high precision using high-performance liquid chromatography (interassay coefficients of variation 4.9 and 4.0%, respectively) and FA using commercial reagents (interassay coefficient of variation 1.65%). All the individuals underwent a 75-g oral glucose tolerance test, which revealed significant correlations between the values of the three glycated proteins and the four plasma glucose concentrations measured as well as the sum of these glucose concentrations, sigma BS (GA, r = 0.80; HbA1c, r = 0.80; FA, r = 0.65). On the basis of the test, 130 of the subjects were classified as normal (N), 123 as borderline and 49 as having diabetes mellitus (D) according to the criteria of the Japan Diabetes Society. Of the 123 borderline cases, 26 showed impaired glucose tolerance (IGT) according to the WHO criteria. The normal group values of GA, HbA1c and FA were 17.8 +/- 0.17% (mean +/- SEM), 5.02 +/- 0.03%, and 2.55 +/- 0.02 mM/l, respectively. Borderline and IGT subjects had significantly more GA and HbA1c than normal but not more FA (P less than 0.01). We divided the subjects into 10 groups on the basis of their sigma BS values; those with values higher than 671 +/- 4.7 mg/dl had significantly more GA and HbA1c than normal, while those with values higher than 1068 +/- 40.9 mg/dl (the most extreme cases) had significantly more FA.(ABSTRACT TRUNCATED AT 250 WORDS)

Modification by catechol and resorcinol of upper digestive tract carcinogenesis in rats treated with methyl-N-amylnitrosamine

Modifying effects of the environmental contaminant catechol, and its isomers resorcinol and hydroquinone, on methyl-N-amylnitrosamine (MNAN)-induced carcinogenesis were studied in male F344 rats. Groups of 15 rats were given three i.p. injections of 25 mg/kg of body weight of MNAN within the initial 2-wk period, and commencing 1 wk thereafter they were administered 0.8% catechol, 0.8% resorcinol, or 0.8% hydroquinone in powdered basal diet or were given basal diet alone for 49 wk. Additional groups of 10 to 15 rats were similarly treated without prior carcinogen exposure. Histological examination after sacrifice at wk 52 revealed that the incidences of tongue papillomas and esophageal squamous cell carcinomas in the groups given MNAN followed by catechol (57.1% and 64.3%) or resorcinol (50% and 58.8%) were significantly higher than those in the carcinogen only controls (9.1, and 0%, respectively). Hydroquinone also enhanced the development of esophageal squamous cell carcinomas but was less active than catechol or resorcinol. The incidence of alveolar hyperplasia in the lungs of the group given MNAN followed by catechol (0%) was, in contrast, significantly reduced as compared to the control value (54.5%). Hydroquinone and resorcinol showed a similar but non-significant tendency. These results indicated that the environmental contaminant, catechol and its isomers, may play a role in the development of human upper gastrointestinal cancer, in addition to exerting modifying effects in other organs.

Transient induction of single GST-P positive hepatocytes by DEN

The single cells positive for placental glutathione S-transferase (GST-P), detectable in livers of rats soon after treatment with hepatocarcinogens, are possible 'initiated cells', the hypothesis tested in the present series of experiments. No low dose threshold was observed in male Sprague-Dawley rats at different single doses of diethylnitrosamine (DEN) although a plateau was reached between 160 and 200 mg/kg body weight. At the latter single dose approximately 12,400 positive cells/cm3 were observed immunohistochemically in rat livers after one week, the numbers then decreasing to week 8 and thereafter rising again. In the early stages single cells predominated but with time a gradual increase in mini-foci and larger lesions became evident. Application of selection pressure (feeding of diet containing 0.02% 2-AAF plus partial hepatectomy) to rats 2-24 weeks after single DEN-treatment resulted in the formation of large foci positive for GST-P, especially in the early stages, the growth response being less pronounced with time. The number of foci, on the other hand, was correlated with the number of single cells/mini-foci detected in hepatectomy tissue of the same individuals. These results suggest that the early GST-P positive populations could be the precursor for preneoplastic foci and nodules.

Strain differences in susceptibility to 2-acetylaminofluorene and phenobarbital promotion of hepatocarcinogenesis: immunohistochemical analysis of cytochrome P-450 isozyme induction by 2-acetylaminofluorene and phenobarbital

Strain differences in the expression of cytochrome P-450 isoenzymes (P-450s) during enhancement of hepatocarcinogenesis by 2-acetylaminofluorene (2-AAF) and phenobarbital (PB) were investigated immunohistochemically using monoclonal antibodies against phenobarbital (PB) (APF3) or 3-methylcholanthrene (3-MC) (APH8) inducible P-450s. LEW, SD, WBN, F344, SHR, NAR, Wistar and ODS rats were studied, the first five strains proving to be less susceptible to 2-AAF induction of APH8 while responding strongly to the promoting influence of this chemical, as reported previously. The other three strains, NAR, Wistar and ODS, demonstrated greater inducibility, this correlating with an observed resistance to promotion by 2-AAF. PB administration was not associated with any strain difference in APF3 cytochrome P-450 inducibility except in the ODS rat, in which its effects were minimal. The results provide direct evidence that differential expression of cytochrome P-450 species plays a major role in determining responsiveness to hepatocarcinogenesis-promoting agents such as 2-AAF.

Synergism between sodium chloride and sodium taurocholate and development of pepsinogen-altered pyloric glands: relevance to a medium-term bioassay system for gastric carcinogens and promoters in rats

In an approach to early detection of gastric carcinogens and promoters in an in vivo test system, promotion by sodium chloride (NaCl) and the synergistic effects of NaCl and sodium taurocholate (Na-TC) on development of pepsinogen-altered pyloric glands (PAPG) in rat glandular stomach after initiation with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated. A total of 205 male WKY/NCrj rats were divided into 8 groups. Group 1 was given a single dose of MNNG of 160 mg/kg body weight by gastric intubation, and starting 2 weeks later basal diet containing Na-TC for 18 weeks. In addition, 1 ml doses of saturated NaCl solution were given by gastric intubation at weeks 4, 6, 8 and 10. Similarly, group 2 was treated with MNNG and Na-TC, while group 3 animals received MNNG and NaCl. Group 4 was given MNNG alone. Groups 5-8 served as equivalent controls without MNNG initiation. The results revealed significantly enhanced induction of immunohistochemically defined PAPG in the Na-TC + NaCl (P less than 0.001), Na-TC (P less than 0.01) and NaCl (P less than 0.01) treated animals initiated with MNNG. Sodium chloride demonstrated a clear synergistic effect with Na-TC in promoting the development of PAPG, suggesting possible advantage for its use in medium-term in vivo assays for detection of gastric carcinogens and promoters.