Effect of dietary selenium and tumor status on the retention of⁷⁵Se by tissues and mammary tumors of DMBA-treated rats

Abstract

The effects of the presence of mammary tumors on⁷⁵Se retention was examined in DMBA-treated rats. Tumor bearing rats fed varying amounts of Se exhibited an inverse linear dose response between dietary Se intake and tissue retention of⁷⁵Se in whole body, heart, lungs, ovaries, adrenals, spleen, and muscle. Tumor⁷⁵Se retention, however, was independent of the dietary intake of Se. Tumor bearing rats excreted more⁷⁵Se label in the urine compared to both control rats fed the same amount of Se and DMBA-treated animals that remained tumor free. In the short term, no significant differences were seen in tissue retention of⁷⁵Se. By 7 d, the increased urinary excretion of the label resulted in significantly decreased retention of⁷⁵Se in blood, spleen, liver, lungs, and kidneys of tumor-bearing rats compared to tumor-free animals. The presence of tumors, however, did not affect the liver distribution of the label among cytosolic proteins. These results suggest that tumor bearing animals have an accelerated urinary excretion of Se compared to animals without tumors and that tumors either have a very slow turnover of Se or a low priority for the element.