THE INFLUENCE OF MELATONIN ON METABOLIC CHANGES IN FEMALE RATS INDUCED BY CONTINUOUS IRRADIATION AND OR ADMINISTRATION OF METHYLBENZ-VERTICAL-BAR-A-VERTICAL-BAR-ANTHRACENE/

Metabolic profile is an important biological marker of neoplastic proc esses not only in the tumor itself but also in the hose organism. The neurohormone melatonin has been implicated in experiments as an oncost atic agent. Female Wistar:Han SPF rats (Velaz, Plague, Czech Republic) were irradiated continuously for 15 days using a daily gamma rays dos e of 96 mGy. At the end of exposure one group of rats was administered 5 mg/kg b.w of dimethylbenz/a/anthracene (DMBA) intragastrically, Dur ing the period of exposure to ionizing radiation a part of the animals was supplied with melatonin (M) at a concentration of 20 mu l/ml in d rinking water, Selected parameters of lipid and carbohydrate metabolis ms and levels of selected hormones were determined 2, 30 and 100 days post-irradiation. The irradiation itself caused only small changes in tissue lipids. The application of a single low dose (subthreshold from the point of view of induction of mammary tumors) of DMBA caused more pronounced changes in nonirradiated animals; of the changes observed an increase in lipids in the liver, triacylglycerols (TG) in the thymu s and decrease in myocardial glycogen predominated. The intake (by dri nking) of exogenous M prevented the biochemical pattern of fatty Liver in animals administered DMBA in both groups, irradiated and nonirradi ated. A prolonged effect of exogenous M, demonstrated by prevention of increase in TG in the thymus and of irradiated animals caused by admi nistration of DMBA, was observed. The mechanism of metabolic effect of M is not known. Additional experiments are needed to explain the rela tionship between the beneficial effect of M on metabolic changes and i ts presumable oncostatic effect in rats.