Effect of Nitrosamine Derivatives on Enzyme Concentrations in Rat Organs During Carcinogenesis

Abstract

SINCE the classical investigations of Warburg, Posener and Negelein (1924) on the glycolytic processes in cancer tissues, the studies dealing with changes of enzymatic processes in relation to cancer have been numerous and are the subject of several reviews, (e.g. Greenstein, 1954; Fishman, 1959). The material studied varies from whole animals to subcellular particles and the significance attributed to the findings differs from causative connection to chance association. Numerous attempts have been made to use the enzymatic changes found in the blood and in the tissues of patients suffering from malignant tumours for diagnostic or prognostic purposes. As the knowledge of the chemistry and morphology of the cellular processes increases, the explanation for the changes of enzymatic processes in tumor cells is modified.The present investigations deal with the effect of the carcinogens dimethyl (DMN) and diethyl (DEN) nitrosamine on the ,3-glucuronidase and lactic dehydrogenase (LDH) activities during the development of tumors in rats. The comparative carcinogenic effect of these substances in the rat has been studied previously (Argus and Hoch-Ligeti, 1961). Changes caused by a carcinogen in the cytoplasmic protein molecules, either directly or consecutive to alteration of template nucleic acids, might manifest themselves in changes of enzyme activities. Methylation of proteins in rat liver slices during incubation with DMN has been described (Magee and Hultin, 1962). With the aid of DMN labelled with radioactive carbon, incorporation of the label into the deoxyribonucleic acid of the liver and probably also of the kidney has been demonstrated. Acid hydrolysis of labelled ribonucleic acid from the liver yielded a 7-methylguanine (Magee and Farber, 1962). The carcinogenic activity of nitrosamine derivatives was thought to be related to protein denaturation (Argus, Leutze and Kane, 1961) or to methylation of sulfhydryl groups in amino acids (Schoental, 1961).The enzyme systems ,8-glucuronidase and LDH were selected for the present study because of their different intracellular distribution. /3-glucuronidase is largely localized in the lysosomes (deDuve, Pressman, Gianetto, Wattiaux and Appelmans, 1955) and, if the intracellular membranes are intact, it is not easily available to substrates. LDH might be localized both in particulate and nonparticulate cellular material. It has been reported to be a mitochondrial enzyme

Enzyme studies of the liver of rats during carcinogenesis by diethylnitrosamine.

“…The weight of heart, lung, kidney, adrenal and thymus did not differ significantly between the treated and control rats. The chronology of the morphological changes in the liver during tumor development was similar to that described previously (Grundmann and Sieburg, 1962;Hoch-Ligeti et al, 1964). Small disseminated groups of highly atypical cells were observed on the 107th day and small multifocal hepatomas were present on the 120th day.…”

“…of tissues duLring carcinogenesis is whether the chainges observed are causally connected with, or concomitant to the development of cancer. Localization and concentration of the same set of enzymes as studied in the present work were investigated in the lung of DEN or DMN treated rats (Hoch-Ligeti, 1966). The changes observed ini the succinoxidase and f-glucuroniidase concentrations were the sarrme as in the liver.…”

“…The rats were killed in pairs, 1 rat from the treated and 1 from the control group. Since in the previous experiment (Hoch-Ligeti et al, 1964) changes in the enzyme concentrations of organs from rats fed DEN were not observed before about the 70th day, only 3 pairs of rats were killed in the present experiment during the first 70 days. After that, at intervals of 7 days, pairs of rats were killed by decapitation with a guillotine and the blood was drained from the opened arteries of the neck.…”

“…In frozen sections cut 30 1 thick in a cryostat, the /3-glucuronidase activity (I hour incubation) was determined by an adaptation of the above method (Hoch-Ligeti et al, 1964).…”

Liver Scarring Induced by Polychlorinated Biphenyl Administration to Mice Previously Treated with Diethylnitrosamine

“…Continuous longterm administration to mice or to rats of carcinogenic dialkyl nitrosamines such as dimethylnitrosamine (DMN) and diethylnitrosamine is accompanied by moderate to extensive proliferation of "oval" cells, bile duct-like structures, and presumably fibroblasts, since collagen also is present in conjunction with the proliferating bile duct-like epithelium (14)(15)(16)(17). We report here that the polychlorinated biphenyl mixture Aroclor 1254 when administered periodically to mice following a short period of DEN exposure results in liver scarring, which does not occur as the result of exposure to the nitrosamine or as the result of treatment with the PCB alone.…”