INFLUENCE OF SELENIUM ON GLUTATHIONE AND SOME ASSOCIATED ENZYMES IN RATS WITH MAMMARY-TUMOR INDUCED BY 7,12-DIMETHYLBENZ(A)ANTHRACENE

A recent finding in epidemiological and laboratory studies suggests th at the ratio of selenium to glutathione is lower in breast cancer subj ects than its control counterparts. Selenium, an antioxidant and antic arcinogen, can modify the status of glutathione and some associated en zymes by blocking peroxidation of lipids in membranes of cancer subjec ts. Studies were conducted using female albino rats of Wistar strain b earing mammary tumor induced by 7,12-dimethylbenz(a) anthracene to ass ess the biological role of selenium on some antioxidant enzymes associ ated with the maintenance of glutathione status. For induction of mamm ary tumor, 25 mg DMBA in a 1 ml emulsion of sunflower oil and physiolo gical saline was injected subcutaneously to each rat. One group in eac h of control and tumor bearing rats, were fed 5 mg sodium selenite/kg diet from the day of tumor induction for 24 weeks. Increase in the red uced glutathione concentration was preceded by significant increase in the oxidized glutathione as well as in the activities of gamma-glutam ylcysteine synthetase, glutathione peroxidase, glutathione reductase, glutathione S-transferase, and glucose-6-phosphate dehydrogenase by se lenium administration in rats bearing tumor. However, selenium adminis tration to rats bearing tumor decreased the activity of gamma-glutamyl transpeptidase. These observations clearly demonstrate the influence of dietary selenium supplementation in correcting abnormal changes in glutathione turnover and some associated enzymes in tumor induced rats .