USE OF INAA TO STUDY THE EFFECT OF SELENIUM ON URANIUM ACCUMULATION IN CELLS OF SACCHAROMYCES-CEREVISIAE

Differences in the effects of seleno-cystine (CySe)2 and inorganic Se( IV) and Se(VI) compounds on uranium(VI) uptake by yeast cells, Sacchar omyces cerevisiae have been studied. The Se, U, Zn and Co levels of th e yeast cells were measured by neutron activation analysis. An increas e in the concentration of U cells within the first 2 hours of incubati on was produced by the presence of SeO2 (2 . 10(-4)-5 . 10(-4)M) and ( CySe)2 (1 . 10(-4)M) in the yeast medium. Moreover, the highest SeO2 c oncentration (5 . 10(-4)M) and (CySe)2 more efficiently enhanced the U content of the cells than SeO2 at the low concentration end (2 . 10(- 4)M). However, the effect of SeO2 and (CySe)2 on U uptake diminishes w ith incubation time (from 2 to 48 hours). Se(VI) [as (NH4)2SeO4] leads to a marked decrease in the content of uranium in Saccharomyces cerev isiae (an antagonistic interaction). As expected, uranium uptake by th e yeast influenced the retention of selenium in the cells. Uranium sig nificantly increased the uptake yield of Se by Saccharomyces cerevisia e when the yeast was incubated in the medium containing (CySe)2. Furth ermore, during the initial 24 hours of the incubation an increase of t he Se content of the cells in the presence of U was observed when Se(V I) was in the culture medium. Selenium and uranium dosages affected th e Zn and Co contents of cells.