Dibenamine: selective protection against diethylnitrosamine-induced hepatic carcinogenesis but not oral, pharyngeal and esophageal carcinogenesis

Oral leukoplakia and costochondral hyperplasia induced by diethylnitrosamine in hamsters exposed to cigarette smoke with or without dietary vitamin C

Male Syrian golden hamsters receiving 12 weekly subcutaneous injections of diethylnitrosamine (DEN) were subjected to cigarette smoke-inhalation and fed a diet or without 1% vitamin C supplement for a period of 58 weeks. Another group was a sham-smoked control and was not fed vitamin C. Tissues of the oral cavity and costal cartilage were examined by light and/or scanning electron microscopy. Oral leukoplakia and costochondral hyperplasia occurred with high frequency in all groups treated with DEN. Leukoplakic lesions were found in the palate, tongue, and pharynx; the early change was focal erosion with mild epithelial hyperplasia and inflammatory cell infiltration. Advanced lesions had marked mucosal thickening due to acanthosis, parakeratosis, hyperkeratosis, and submucosal infiltration of lymphocytes and plasma cells. Precancerous lesions were noted in tongue and pharynx. Scanning electron microscopy of tongues revealed destruction of filiform papillae. The incidence of leukoplakic lesions were higher in smoke-exposed hamsters than in controls, but the incidence in vitamin C-supplemented hamsters was low when compared with the smoke-exposed hamsters without vitamin C. Costochondral hyperplasia was initiated by thickening of the perichondrium followed by proliferation of chondrocytes. Costochondral hyperplasia appeared earlier, and the incidence was higher in the vitamin C-supplemented hamsters. It could not be determined whether costochondral hyperplasia was the primary lesion induced by DEN or secondary change.

Central mechanism of vinblastine inhibitory effect on experimental carcinogenesis

In the experiments carried out on white male rats the effect of vinblastine on the development of malignant stomach tumours induced with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) has been studied. The combined administration of MNNG and vinblastine inhibits the experimental carcinogenesis at the stage of "intestinalization" and decreases the indicence of stomach adenocarcinomas by 3-fold. Pharmacological analysis using the application of apomorphine stereotypy showed the antagonism of MNNG and vinblastine at the level of central parts of the autonomic nervous system due to the inhibition of axoplasmic transport of catecholamines. These results confirm the earlier data on the essential role of catecholamines in the mechanisms of carcinogenic action of nitrosamines.

Morphopharmacological analysis of the carcinogenic properties of N-methyl-N'-nitro-N-nitrosoguanidine

The modifying influence of atropine and reserpine on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) induction of stomach tumors was studied in experiments on 120 random-bred male white rats. At the same time, pharmacological analysis of the mechanism of the carcinogenic action of MNNG was carried out. Atropine stimulated and reserpine markedly inhibited the carcinogenic effect of MNNG. MNNG interference altered the specific effects of amphetamine and phenobarbital. These alterations are due to the MNNG damage of the permeability of the presynaptic membrane of the central adrenergic structures. The leading role of adrenergic influences on the presence of carcinogenic transformation of stomach cell processes is discussed.