Histopathological studies on renal tubular cell tumors in rats treated with N-ethyl-N-hydroxyethylnitrosamine.

Administration of a diet containing 0.2% N-ethyl-N-hydroxyethylnitrosamine (EHEN) for 2 weeks induced hepatocellular carcinoma in 3 and renal tubular cell tumors in 7 of 9 Wistar rats. Diet containing 0.1% EHEN induced renal tubular cell tumors in 6 of 10 rats, but no hepatocellular carcinomas. Both diets induced atypical cell population of tubules in the kidney, but no nephroblastoma.

Mesotheliomas and proliferative lesions of the testicular mesothelium produced in Fischer, Sprague-Dawley and Buffalo rats by methyl(acetoxymethyl)nitrosamine (DMN-OAc).

A single intraperitoneal dose of methyl(acetoxymethyl)nitrosamine (13 mg/kg body weight) given to 78 5-week-old male rats induced 25 mesotheliomas; two mesotheliomas were found in 67 control rats. All mesotheliomas arose from the peritesticular mesothelium and had a typical microscopic appearance of branching papillary fronds with a collagenous core covered by one or many layers of plump tumor cells. Cytoplasm of tumor cells contained material that reacted positively to a colloidal iron stain and was labile to hyaluronidase. In addition to frank mesotheliomas, 16 lesions, which we called atypical mesothelial proliferations, were found. These consisted of a single focus of plump mesothelial cells overlying an area of thick stroma. Often these foci included short, non-branched papillary projections above the surface of adjacent normal mesothelium. Twelve of the 16 lesions occurred in methyl(acetoxymethyl)nitrosamine-treated rats.

Induction of renal pelvic tumours in Sprague-Dawley rats by di-isopropanolnitrosamine.

Transitional cell papillomas and carcinomas of the renal pelvis were observed in Sprague-Dawley rats after subcutaneous (s.c.) treatment with di-isopropranolnitrosamine (DIPN). These tumours occurred unilaterally and appeared as early as 24 weeks after the commencement of treatment. The tumours frequently filled the entire renal pelvis and compressed the kidney parenchyma. The malignant neoplasms demonstrated infiltrative growth into the adjacent medullary parenchyma.

Mutagenic selectivity of carcinogenic nitroso compounds: III. N,alpha-acetoxymethyl-N-methylnitrosamine.

A comparative genetic study was undertaken on the testicular tissue of Drosophila with N-alpha-acetoxymethol-N-METHYLNITROSAMINE (AcODMN) and its unsubstituted parent N,N-dimethylnitrosamine (DMN), to assess the role of intracellular metabolism on their mutagenicities. The relative genetic potencies of the two compounds were deduced from regression studies of the dose effect on the metabolically inert sperm and the metabolizing early germ cells (spermatocytes and spermatogonia) with respect to the induction of the non-specific X-chromosome recessives (lethals and visibles) and the specific effects on representatives of the RNA genes, especially rDNA. Genetic activity per unit molar dose was invariably higher for the acetoxy derivative as compared to the parent amine, but the differential in this respect varied significantly for various mutational classes and as a function of the metabolic level in the target cells. The induction of point-mutations (X-recessives) increased with the level of intracellular metabolism with bothe compounds and this was more pronounced with the parent amine, which was in accordance with the DNA methylation mechanism. In contrast, the yield of the specific rDNA deletions was not markedly enhanced with the increased metabolic activity in the early germ cells, especially with the acetoxy derivative. The induction of these deletions could not, therefore, be explained on the basis of DNA methylation, but was reconcilable with the posible generation of a nitroso-aldehydic metabolite, which could effect DNA-protein cross-linkage within the genic nucleoproteins. The two test compounds gave comparable frequencies of mosaicism among corresponding mutations and the same rDNA selectivity index, which indicated identical molecular mechanisms of mutagenesis. The higher genetic potency of the acetoxy derivative as compared to the parent amine would thus be indicative of its greater yield of the same mutagenic metabolites. Carcinogenicity studies with the two compounds paralleled the mutagenicity results, which whould suggest that the same molecular mechanisms could well be responsible for the initiation of both phenomena.

The interaction of acetoxy-dimethylnitrosamine, a proximate metabolite of the carcinogenic amine, and bacteriophages R17 and T7.

The biological and physicochemical effects of reacting bacteriophages R17 and T7 with acetoxy-dimethylnitrosamine (ADMN) have been studied. The rate-determining step in the reactions appeared to be the loss of the acetoxy group by hydrolysis, the hydroxymethyl-methylnitrosamine generated decomposing rapidly to give a methyldiazonium ion and formaldehyde. In experiments with bacteriophage suspended in phosphate buffer the biological inactivation observed was the sum of the effects of the formaldehyde and of alkylation by the methylcarbonium ion produced from the diazonium ion. In experiments with bacteriophage suspended in Tris--HCl buffer the effects of formaldehyde were eliminated by its reaction with the buffer component. Alkylation by the carbonium ion produced unstable phosphotriesters in the bacteriophage RNA which on hydrolysis led to degradation of the molecule. In phosphate buffer the formaldehyde cross-linked the protein coat of the bacteriophage blocking the extraction of the RNA. Estimates of the mean lethal dose and of the extent of degradation of the RNA following reaction in Tris--HCl buffer were fairly close to those observed in experiments with N-methyl-N-nitrosourea (MNUA).

Ultrastructure and formation of lamellated inclusion bodies in induced lung tumors of the European hamster.

Utlrastructure and formation of lamellated inclusion bodies (LB) in N-dibutyl-nitrosamine-induced lung tumors in European hamsters are described. Two types of LBs are observed: one with cross-barred lamellae and one with concentric lamellae. Both types develop from lysosome-like dense bodies which are formed by the Golgi apparatus. More mature forms fuse with rough endoplasmic reticulum (RER). Mature LBs migrate to the cell surface, where their contents are extruded into the alveolar lumen by means of a merocrine secretion. The extruded lamellae give rise to the myelin figures and lattices that are reported to possess surfactant properties.

Mass spectrometry of nitrosamines: rearrangement of nitrosobenzylmethylamine molecular ions with loss of OH-radicals investigated by deuterated derivatives.

Nitrosamines (R1R2NO) containing a certain R groups yield mass spectra with M+-OH fragments which can be accounted for by intramolecular hydrogen shift with subsequent cleavage of OH-radicals. As can be shown with mass spectra of specifically deuterated derivatives of nitrosobenzylmethylamine - nitrosobenzyltrideuteriomethylamine, alpha,alpha-nitrosodideuteriobenzylmethylamine and o,o',p-nitrosotrideuteri0-benzylmethylamine - hydrogen transfer within the molecular ion of nitrosobenzylmethylamine occurs selectively onto the oxygen of the nitroso group from the benzylethylene group, probably via a five-membered cyclic transition state. Cleavage of OH radicals leads to formation of M+-17 ions, the stability of which can be explained by mesomerically stabilized cyclic diazirinium ions.