On the Oxidative Metabolism of the Rat Skin during Carcinogenesis induced by 7,12-dimethylbenz[a]anthracene

Abstract

The oxidation rate of citrate, d,1-isocitrate, glucose-6-phosphate and phosphogluconate proceeded two fold more rapidly in slices of rat skin with tumors induced by 7,12-dimethylbenz[a]anthracene than in normal skin. Citrate oxidation was stimulated by addition either of Fe⁺⁺ or of cysteine, which, when both present in the system, are able to avoid the aconitase inactivation in the tissue. Mn⁺⁺, NADP, FMN and cytocrome c may activate the oxygen uptake both in normal and pathological tissues, using as substrates respectively citrate, d,1-isocitrate, glucose-6-phosphate or phosphogluconate. The isocitric-dehydrogenase activity of the extracts of tumor induced rat skin resulted lower than that observed in normal rat skin; glucose-6-phosphate and respectively phosphogluconate-dehydrogenase enzymatic levels were two fold higher in the neoplastic than in the normal skin rat extracts. The results presented show an increase of the oxidative carbohydrate metabolism and pentosephosphate shunt, during carcinogenesis in the rat skin.