[Autoradiographic studies on RNA metabolism during dibutylnitrosamime-induced bladder tumors in rats]

Protective role of soybean feeding against the cytogenetical and histopathological effects of dibutylamine and sodium nitrate on bone marrow and liver of mice

The protective role of soybean feeding against the cytogenetic and histopathologic effects of the nitrosamine precursors sodium nitrate and dibutylamine was evaluated. Treated animals were killed every 3 months, over a period of 15 months, and bone marrow cells were prepared for cytogenetic studies and livers for histopathological observations. Structural chromosomal aberrations and mitotic indices increased after treatment with the nitrosamine precursors for all tested times. Livers were within the normal appearance during the first 6 months. After that a mild, moderate, marked dysplasia with lymphocytic infiltration, fatty vacuolation and liver atrophy was observed. Soybean coadministered with the nitrosamine precursors reduced the number of structural chromosomal aberrations. Mitotic indices decreased at all tested groups but still higher than the control level. A marked reduction in dysplastic features in the liver cells was observed. In conclusion, the cytogenetic and histopathologic results of this study strongly support the protective role of soybean against the genotoxic and carcinogenic action of nitrosomine formed in vivo from its precursors.

Comparison of enzyme phenotypes in human bladder tumours and experimentally induced hyperplastic and neoplastic lesions of the rat urinary bladder. A combined histochemical and immunohistochemical approach

The expression of a number of enzymes involved in drug metabolism, membrane function etc. was compared in hyperplastic and neoplastic lesions of the rat bladder and in human bladder tumours. Transitional cell carcinomas (TCC) in both rat and Man were characterized by decreased alkaline phosphatase (ALP) and increased gamma-glutamyl transpeptidase (GGT), beta-glucuronidase (beta-G1), succinate dehydrogenase (SD) and glucose-6-phosphate dehydrogenase (G6PD) activities. In addition, binding for antibodies specific for different cytochrome P-450 species (UT50, PB3a, MC1, MC2) and microsomal epoxide hydrolase (mEHb) was elevated in both murine and human tumours. Comparison of the enzyme phenotype in hyperplastic lesions induced by freeze ulceration or uracil administration with that in preneoplastic papillary or nodular hyperplasia (PNH) and TCC suggested, however, that most of the alteration in enzyme content or activity was non-specific and related to requirements for epithelial cell proliferation. On the other hand, the decreased ALP, and increased GGT and beta-G1 activity appeared more directly related to neoplastic transformation. The results suggested that qualitative differences exist between reactive hyperplasia and preneoplastic or neoplastic lesions in the urinary bladder. The finding of increased cytochrome P-450, in clear contrast to the reduction characteristic of preneoplastic hepatic lesions, may be important with regard to the observed difference in neoplastic transformation between the bladder and liver in response to drug metabolising enzyme inducers.

Mutagenic activation of dialkylnitrosamines by intact urothelial cells

Intact urothelial cells isolated from bladders of untreated inbred NZO/BIGd or NZC/BIGd mice and NZR/Gd rats activated dimethyl, diethyl, dipropyl, and dibutyl nitrosamines in a liquid culture mutagenesis fluctuation assay using Salmonella typhimurium TA100 as target organism. Rat and mouse urothelial cells were highly effective at 1.5 X 10(5) cells/ml, in O2 gas phase, and no cofactors were required. Relative mutagenic activities were estimated at equitoxic (LD50) concentrations of the 4 nitrosamines. Nitrosamines with odd-carbon chain substitutents were more active than the C-even compounds. Although dibutylnitrosamine is a powerful bladder carcinogen in both rats and mice while the other 3 compounds very rarely cause bladder tumours, the most active promutagens were dipropyl and dimethyl, followed by diethyl and dibutyl nitrosamines. None were active in absence of urothelial cells. Mouse bladder cells were more active than those from NZR rats. There were sex differences in the mice with NZC males and NZO females predominating, but in NZR rats urothelial cells from male and female animals were equally active. These dialkylnitrosamines are widely distributed in the environment, and our results indicate that direct mutagenic activation in the urothelium could be one factor contributing to the incidence of bladder cancer.

[Stimulating effect of partial cystectomy on regeneration of rat bladder urothelium and its significance for carcinogenesis (author's transl)]

Cell proliferation kinetics of the urinary bladder urothelium have been analyzed in a total of 218 female Wistar rats after partial cystectomy. After one-third resection of the bladder DNA synthesis started 15 h postoperatively in the bladder stump and reached its maximum at 25 h with a mean 3H-TdR index of 10.1%. In the area of resection the proliferative activity increased after 20 h and the highest 3H-TdR index was found to be 24.7% after 45 h. In the case of hemicystectomy the labeling index in the stump increased 15 h postoperatively and the highest 3H-T-dR index was determined at 20 h with 16.6%. The urothelial cells in the area of resection began to proliferate synchronously with those in the stump and the maximum of DNA synthesis was measured 35 h postoperatively with an 3H-TdR index of 24.2%. After 2 weeks the proliferative activity within the stump and operative region corresponded to that of the control urothelium. The basal cells showed absolutely the highest proliferative activity, the suprabasal cells exhibited on the other side the highest regenerative potential compared with the control urothelium. Partial cystectomy might possibly serve as an experimental model for testing low potential carcinogens, in the case where carcinogenic effects would be initiated, potentiated and accelerated via stimulation of the DNA synthesis.

Stages of transformation in the development of N-butyl-N-(4-hydroxybutyl)-nitrosamine-induced transitional cell carcinomas in the urinary bladder of rats

The histogenesis of papillary and nonpapillary transitional cell carcinomas were studied morphologically and autoradiographically in 177 female Wistar rats after oral application of N-butyl-N-(4-hydroxybutyl)-nitrosamine with varying exposure and induction times. By far the largest proportion of carcinomas developed by a malignant transformation of preexisting papillomas or their precursors, the papillary hyperplasias. The transition into a focally malignant growth did not take place abruptly, but occurred stepwise through different successive stages of transformation, each having its own distinct morphological character. The first stage consisted of a focal, sharpely defined cellular atypia. In a further stage carcinomata in situ developed out of the atypical foci and progressed finally in a last stage of transformation into a circumscript infiltrative growth. The successive development of each stage occurred independent of any further carcinogen application after transformation was initiated at the molecular level. The number of papillomas with transformation stages increased with a lengthening of the exposure and induction time. 74.4% of all the registered papillomas had been transformed. Consequently papillomas must be considered potentially highly malignant. The 3H-TdR index was 4.2 times higher in atypical urothelial areas (7.6%) and 7.5 times higher in carcinomata in situ (14.3%) than in the surrounding papillomatous structures which appeared light microscopically benign. The latter demonstrated a rather constant 3H-TdR index, whether they bordered on atypical foci (1.8%) or carcinomata in situ (1.9%). The length of exposure and induction time exercised no significant influence on the degree of proliferative activity. The development of transitional cell carcinomas from a primary carcinoma in situ (intraurothelial carcinoma) played a much less significant role.

Focal loss of alkaline phosphatase and increase of proliferation in preneoplastic areas of the rat urothelium after administration of n-butyl-n-(4-hydroxybutyl)-nitrosamine and n-[4-(5-nitro-2-furyl)-2-thiazolyl] formamide

Development of tumours of the urinarY bladder was studied in 59 Male and female Sprague-Dawley and Wistar rats with combined enzyme-histochemical and autoradiographic methods after oral application of n-butyl-n-(4-hydroxybutyl)-nitrosamine (BBN) and n-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide (FANFT). as the first carcinogenic lesion detectable by light-microscopy a focal, sharply defined irreversible loss of alkaline phosphatase activity was consistently demonstrated in the urothelium, which appeared normal histologically and cytologically. In about 2/3 of the cases, NADH-diaphorase activity was markedly reduced in identical regions. The enzyme-deficient areas are to be considered as preneoplastic, because papillomas and carcinomas developed from them through different stages of hyperplasia. As a rule, these also were characterized by total loss of alkaline phosphatase activity and attenuation of the NADH-diaphorase in all parts or circumscribed areas. Autoradiographically 3H-thymidine-labelling index revealed a 43.2-fold (BBN) and 22.6-fold (FANFT) increase, respectively, in the enzyme-deficient areas, as compared with the surrounding emzyme-containing urothelium. After 54 hrs of continous labelling, there was a mean 3H-thymidine-labelling index of 54.9% in the enzyme-negative regions. The physiological mode of regeneration was no longer maintained in the areas of enzyme deficiency as there was an increased proliferation of suprabasal cells. Areas of papillomas that showed a marked attention of NADH-diaphorase had a 3H-thymidine-labelling index 4.5 (BBN) and 3.1 (FANFT) greater than the surrounding areas with preserved enzyme activity. Since loss of alkaline phosphatase activity occurs regulary and consistently after application of carcinogens with chemically different structures it appears to indicate the initial phase of tumor development in the urinary bladder of the rat.