H. Urban

The proliferative activity of the adrenal cortex as influenced by carcinogenic and noncarcinogenic substances

A single oral toxic dose of carcinogens (N-nitrosomorpholine, aflatoxin B1, N--methyl-N-nitrosourea, urethan) causes a significant increase of the mitotic rate in the adrenal cortex 48 hours after application. Both, the control animals (water via stomach tube) and the animals treated with acetylsalicylic acid, arsenic, phenol and actinomycin D do not produce this effect. These findings confirm our previous results obtained by administration of acetylaminofluorene, diethylnitrosamine, dimethylnitrosamine and trinitroso-trimethylen-triamine. It is possible that the increased mitotic activity of the adrenal cortex is correlated with the substances applied.

The modification of tat liver regeneration by carcinogens and its reflection by extrahepatic tissues

Liver regeneration is distinctly influenced by the treatment of male Sprague-Dawley rats with 2-acetylaminofluorene or N-methyl-N-nitrosourea on three successive days immediately prior to partial hepatectomy. The latter compound modulates the restorative liver growth, whereas it is strongly inhibited by the hepato-carcinogen 2-acetylaminofluorene. According to their influence on the regenerating liver, both carcinogens delay the post-operative decrease as well as the recovery of the physiological cell renewal in the jejunal and esophageal epithelium. Beside this, the circadian mitotic fluctuation of the esophagus is also altered by the carcinogens after partial hepatectomy like that of the regenerating liver. In contrast to the behaviour of the jejunum and the esophagus, the adrenocortical cell division is temporally elevated by the growth stimulus after partial hepatectomy. This effect is also found after carcinogen pretreatment only. For that reason one can assume that carcinogens produce a growth stimulating response like partial hepatectomy, which is displayed by an increased cell replication in the adrenal cortex. Possibly this phenomenon reflects common systemic mechanisms which indicate the promotory action of partial hepatectomy and chemical promotors as well as that of carcinogens.

Growth stimulation following serum transfer from carcinogen-treated donors to normal rats: a new aspect of early carcinogen actions.

Especially in their early phase of action carcinogens are strong inhibitors of cell proliferation. This is an apparent contradiction to the promoting activity of oncogens in the process of carcinogenesis. Because of obvious similarities between restorative and neoplastic growth processess on the tissue level we have studied the possibility, whether such similarities do exist also with regard to stimulatory activities in the serum. To overcome the non-specific inhibitory effect of a carcinogen, the serum of 2-acetylaminofluorene (AAF) treated male Sprague-Dawley rats was transferred to normal recipients. The results demonstrate that the proliferation of the same tissues (hepatocytes, adrenocortical cells, thymocytes) as in liver regenerating animals were stimulated by the serum of the carcinogen-treated rats. Whether the observed short-term effect corresponds to the so-called promoting activity of the carcinogen(s) is discussed. Nature and origin of the humoral stimulator(s) are still unknown.

N,N-diethyl-4-aminoazobenzene (DEAB): acute actions with respect to possible carcinogenicity as well as the role of solvents. Morphological and pharmacological investigations

The acute action of the azo dye DEAB was investigated in Sprague-Dawley (SD) and Wistar (Wi) rats. The substance was dissolved both in DMSO and sunflower oil and was administered once by stomach tube. Cytochrome P-450-DEPENDENT N-demethylation of ethylmorphine and dimethylnitrosamine are differentially altered depending on the solvent used. The excretion of DEAB as well as of N,N-dimethyl-4-amino-azobenzene (DAB) is delayed and diminished if the substances are dissolved in DMSO. Beside these effects the mitotic number in the adrenal cortex is significantly elevated in both strains of rats. But, in SD rats only DMSO-solution of DEAB is effective. In Wi rats both are effective, the oily solution more than that in DMSO. In this respect DEAB resembles DAB and various other carcinogens which are efficient in stimulating adrenocortical cell division. Considering the positive short-term assay after three other substances which revealed carcinogenic properties in long-term experiments we conclude that also DEAB may be carcinogenic in adequate long-term examination.

The action of a single toxic dose of 2-acetylaminofluorene or allylic alcohol on the adrenals. I. Behaviour of organ weight and mitotic activity of the adrenocortical cells.

In male Sprague-Dawley rats the relative organ weight and mitotic activity of the adrenal cortex were investigated after intoxication by a single dose of 200 mg/kg b.w. of 2-acetylaminofluorene (AAF) or 20 mg/kg b.w. of allylic alcohol (ALL). 36, 42, 48 and 72 hours after application a significant enhancement of the mitotic rate of the adrenocortical cells was produced by AAF in comparison with that following ALL administration. Interrelations of organ weight and proliferative activity could not be found.

Tumor-inducing effect of trinitroso-trimethylene-triamine (TTT) when orally applied in dimethylsulphoxide (DMSO) for solvent.

By oral application of TTT, disolved in concentrated DMSO, it was possible by means of a long-term experiment to produce tumors in female rats (Wistar strain). Contrary to all previous findings the tumor-inducing effect of this substance has been proved in this way for the first time.