Immunohistochemical and biochemical identification of pepsinogen isozymes in the hamster lungs: induction by polychlorinated biphenyls.

Pepsinogens are acid protease enzymes of pepsin usually found in gastric mucosa. In the present study, we demonstrated the presence of pepsinogen isozymes in male Syrian golden hamster lung tissues by a combined immunohistochemical and biochemical approach. Immunohistochemically, using rat pepsinogen 1 antibody, pepsinogen positive cells were observed mainly in the epithelia of the terminal bronchioles. They demonstrated morphological features of Clara cells. The pepsinogen isozyme pattern of lung tissue determined by polyacrylamide gel electrophoresis was similar to that of stomach mucosa. Treatment of hamsters with polychlorinated biphenyls at a dose of 500 mg/kg body weight ip caused a 2.8-fold increase in pepsinogen content (p less than 0.01) as well as increase in numbers of pepsinogen positive cells in the lung.     

Renal cell adenomas and carcinomas in hemodialysis patients: Relationship between hemodialysis period and development of lesions

Step-sections of 96 whole kidneys from 50 chronic hemodialysis patients were subjected to a histopathological and quantitative investigation with regard to the development of renal neoplastic lesions. The range of hemodialysis duration was from 1 to 222 months. A total of 349 renal cell adenomas were found in 41 cases (82%). They were commonly multiple and present bilaterally. Renal cell carcinomas were evident in four cases (8%), with hemodialysis durations of 54, 57, 112 and 222 months. The incidence of adenomas increased in a hemodialysis duration-dependent manner, indicating a high risk of renal cell tumor development in chronic hemodialysis patients. Furthermore, acquired cystic disease of the kidney (ACDK) was also observed in 12 cases (24.0%), where the mean hemodialysis period was 143.4 ± 48.0 months. This value was significantly longer than that of non-ACDK cases (P < 0.001). There was, however, no clear relationship between the appearance of ACDK and renal cell tumors. The present results underline the necessity for attention to possible neoplasia of the kidney in patients on long-term hemodialysis.     

Modifying effects of 1'-acetoxychavicol acetate (ACA) and the novel synthetic retinoids Re-80, Am-580 and Am-55P in a two-stage carcinogenesis model in female rats

Effects of dietary administration of 1'-acetoxychavicol acetate (ACA) and the novel synthetic retinoids 4-[1-hydroxy-3-oxo-3-(5,6,7,8-tetrahydro-3-hydroxy-5,5,8,8-tetramethyl-2-naphthalenyl)-1-propenyl]benzoic acid (Re-80); 4-[(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenyl)carboxamido]benzoic acid (Am-580); and 6-[(3,5-di-tert-butylphenyl) carbamoyl]nicotinic acid (Am-55P) were examined using a two-stage rat carcinogenesis model. A total of 190 female SD rats was treated sequentially with 1,2-dimethylhydrazine (DMH, s.c.); 7,12-dimethylbenz(a)anthracene (DMBA, i.g.); and 2,2'-dihydroxy-di-n-propylnitrosamine (DHPN, in the drinking water) during the first three weeks (DDD-initiation), and an additional 60 rats received the vehicle alone (non-initiation). One week after the completion of the initiation period, they were divided into nine groups and administrated Re-80 (at dose levels of 1.0 or 0.4 ppm), Am-580 (20 or 4 ppm), Am-55P (20 ppm), ACA (100 ppm), all-trans-retinoic acid (10 or 2 ppm) or no supplement in the diet for 33 weeks, until survivors were euthanatized at week 37 weeks. After DDD-initiation, all-trans-retinoic acid at the high dose delayed the development of mammary tumors. The multiplicity of colon tumors in the group fed Am-55P and the incidences of nephroblastomas with ACA or Am-580 were decreased as compared with the control values, but the other chemicals had no modifying effects on tumor development in any organs. Thus, among ACA and the novel synthetic retinoids tested, only Am-55P showed a weak inhibitory effect on a neoplasm of general interest under the present experimental conditions.     

Lack of synergism among DMAB, BOP, and MNU in induction of carcinomas of the rat ventral prostate.

The present experiment was undertaken to investigate possible synergism in induction of rat prostate tumor. F344 rats were repeatedly administered the prostate carcinogens 3,2'-dimethyl-4-aminobiphenyl (DMAB),N-nitrosobis(2-oxopropyl)amine(BOP), and N-methylnitrosourea (MNU) sequentially or together at times of hormonal castration induced regenerative cell proliferation of prostate epithelial cells. Group 1 animals received two 100 mg/kg doses of DMAB, two 20 mg/kg applications of BOP, and two times 15 mg/kg of MNU. Groups 2, 3, and 4, respectively, received each of the carcinogen treatment alone. Group 5 was given 6 applications of all three in combination, each at one-third the dose administered to the other groups. The results showed a clear synergism in enhanced tumor development in the colon but not in the prostate, in which the incidence of lesions induced by the three carcinogens was similar to that with DMAB alone.     

The 1.5 GHz Electromagnetic Near-field Used for Cellular Phones Does Not Promote Rat Liver Carcinogenesis in a Medium-term Liver Bioassay

We have recently established that local exposure to a 929.2 MHz electromagnetic near-field, used for cellular phones, does not promote rat liver carcinogenesis in a medium-term bioassay system. In the present study, a 1.439 GHz electromagnetic near-field (EMF), another microwave band employed for cellular phones in Japan, was similarly investigated. Time division multiple access (TDMA) signals for the Personal Digital Cellular (PDC) Japanese cellular telephone standard system were directed to rats through a quarter-wavelength monopole antenna. Numerical dosimetry showed that the peak SARs within the liver were 1.91–0.937 W/kg, while the whole-body average specific absorption rates (SARs) were 0.680–0.453 W/kg, when the time-averaged antenna radiation power was 0.33 W. Exposure was for 90 min a day, 5 days a week, over 6 weeks, to male F344 rats given a single dose of diethylnitrosamine (200 mg/kg, i.p.) 2 weeks previously. At week 3, all rats were subjected to a two-thirds partial hepatectomy. At week 8, the experiment was terminated and the animals were killed. Carcinogenic potential was scored by comparing the numbers and areas of the induced glutathione S-transferase placental form (GST-P)-positive foci in the livers of exposed (48) and sham-exposed rats (48). Despite increased serum levels of corticosterone, adrenocorticotropic hormone (ACTH) and melatonin, the numbers and the areas of GST-P-positive foci were not significantly altered by the exposure. These findings clearly indicated that local body exposure to a 1.439 GHz EMF, as in the case of a 929.2 MHz field, has no promoting effect on rat liver carcinogenesis in the present model.     

Effects of urinary crystals induced by acetazolamide, uracil, and diethylene glycol on urinary bladder carcinogenesis in N-butyl-N-(4-hydroxybutyl)nitrosamine-initiated rats

In order to examine the promoting effect of urinary crystals on urinary bladder carcinogenesis, acetazolamide, uracil, and diethylene glycol, all of which have been reported to cause urinary crystals or calculi, were administered to male F344 rats for 32 weeks after pretreatment with 0.05% N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) for 4 weeks. A marked increase in urinary crystals was observed in acetazolamide-treated rats and a slight increase in crystals was observed in uracil- and diethylene glycol-treated rats. Histological examination of the urinary bladder revealed that the BBN-acetazolamide treatment resulted in a higher incidence of carcinoma than BBN-control. Uracil and diethylene glycol did not cause any significant difference compared to the control. Promoting effects by urinary crystals were not clearly shown in the present experiment and, therefore, urinary crystals appear to play a very limited role, if any, in urinary bladder carcinogenesis.     

Increased gap junctional intercellular communication capacity and connexin 43 and 26 expression in rat bladder carcinogenesis

Many reports have suggested that gap junctional intercellularcommunication or gap junction proteins (connexins) could havetumor suppression characteristics. We investigated gap junctionalintercellular communication capacity and connexin 26, 32 and43 mRNA expression in four rat bladder cell lines and the resultswere compared to their tumorigenicity. We also examined connexinexpression in rat bladder carcinomas induced by 3,2'-dlmethyl-4-aminobiphenylor N-ethyl-N-(4-hydroxybutyl)nitrosamine (EHBN) and in normalbladders. There was clear tendency that cell lines with greatercommunication had stronger tumorigenicity and more expressionof connexin 26 or 43. We could not detect connexin 32 in thesecell lines. In normal bladder tissue, connexin 43 expressionwas barely detectable and there was no detectable connexin 26.However, in rat bladder carcinomas, especially the EHBNinducedcarcinomas, abundant expression of both connexins was observed.These results indicate that increased gap junctional intercellularcommunication capacity or increased connexin(s) expression maygive a growth advantage in rat bladder carcinogenesis.     

Analysis of Synergism in Hepatocarcinogenesis Based on Preneoplastic Foci Induction by 10 Heterocyclic Amines in the Rat

The effects of simultaneous treatment with 5 or 10 heterocyclic amines at low dose levels on hepatocarcinogenesis in rats were investigated using a medium-term liver bioassay protocol based on the two-stage carcinogenesis hypothesis with diethylnitrosamine initiation (200 mg/kg, i.p.). Five carcinogenic heterocyclic amines in experiment 1 (Trp-P-1, Glu-P-2, IQ, MelQ, MelQx) and experiment 2 (Trp-P-2, Glu-P-1, MeAαC, AαC, PhIP) were administered together or individually in the diet at levels of 1/1, 1/5, or 1/25 careinogenic doses, and all 10 chemicals were given at 1/10 or 1/100 levels in experiment 3. Induction of preneoplastic glutathione S -transferase placental form (GST-P)-positive foci in the liver was generally increased in the combination groups over the sums of the 5 or 10 individual effects. Thus, based on the heteroadditive concept, synergism was observed for each combination, being most obvious in the group given all 10 chemicals at the 1/10 dose levels. However, the values for the combined groups were generally close to the averages of the 5 or 10 data gained for the heterocyclic amines alone at the corresponding higher doses, indicating the possibility of isoadditivity. Based on these findings, we propose here a new statistical method for analysis of combined effects of multiple chemicals, and, using this, we demonstrated (true) synergism with some heterocyclic amine combinations. The importance of dose-response curves for evaluation of combination effects is discussed.     

Prevention by natural food anthocyanins, purple sweet potato color and red cabbage color, of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-associated colorectal carcinogenesis in rats initiated with 1,2-dimethylhydrazine

The potential of purple sweet potato color (PSPC) and red cabbage color (RCC), natural anthocyanin food colors, to modify colorectal carcinogenesis was investigated in male F344/DuCrj rats, initially treated with 1,2-dimethylhydrazine (DMH) and receiving 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in the diet. After DMH initiation, PSPC and RCC were given at a dietary level of 5.0% in combination with 0.02% PhIP until week 36. No PSPC or RCC-treatment-related changes in clinical signs and body weight were found. Incidences and multiplicities of colorectal adenomas and carcinomas in rats initiated with DMH were clearly increased by PhIP. In contrast, lesion development was suppressed by RCC, or tended to be inhibited by PSPC administration. Furthermore, in the non-DMH initiation groups, induction of aberrant crypt foci (ACF) by PhIP was significantly decreased by RCC supplementation. The results thus demonstrate that while PhIP clearly exerts promoting effects on DMH-induced colorectal carcinogenesis, these can be reduced by 5.0% PSPC or 5.0% RCC in a diet under the present experimental conditions.     

Chemoprevention of 2-amino-1-methyl-6-phenylimidazo- [4,5-b]pyridine-induced colon carcinogenesis by 1-O-hexyl-2,3,5-trimethylhydroquinone after initiation with 1,2-dimethylhydrazine in F344 rats

The aim of this study is to investigate the chemopreventive effects of the synthetic phenolic antioxidant 1-O-hexyl-2,3, 5-trimethylhydroquinone (HTHQ) on 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-associated colon carcinogenesis in rats after initiation with 1,2-dimethylhydrazine (DMH) in male F344 rats. Groups of 20-22, 6-week-old male F344 rats were given four subcutaneous injections of 40 mg/kg body wt of DMH during the initial 4 weeks. They were then maintained on powdered basal diet containing 0.03% PhIP alone, PhIP together with 0.5 or 0.125% HTHQ, 0.5 or 0.125% HTHQ alone or basal diet for 32 weeks. A small number (1.1 +/- 1.1/rat) of colon tumors were induced by DMH treatment alone. After initiation with DMH, the number of colon tumors was greatly increased to 8.3 +/- 5.6 by the administration of PhIP. Additional treatment with HTHQ dose-dependently decreased the multiplicity of colon adenocarcinomas to 4.9 +/- 2.8 and 2.6 +/- 1.4 with 0.125 and 0.5%, respectively. This treatment similarly reduced atypical hyperplasias of the ventral prostate. Furthermore, HTHQ significantly reduced the multiplicity of duodenal adenocarcinomas induced by DMH + PhIP or DMH alone. Immunohistochemically, HTHQ was revealed to suppress PhIP-DNA adduct formation in the epithelial cells of the colon and prostate in a separate 2 weeks experiment. The present results clearly showed that HTHQ has chemopreventive potential for PhIP-associated colon and prostate carcinogenesis. The observed inhibition may largely be due to interference with PhIP-DNA adduct formation. In addition, HTHQ has been demonstrated to inhibit duodenal carcinogenesis in the post-initiation stage.