Use of INAA to study the determination of Se, Th, Zn, Co and Fe levels of yeast cells

Differences in the effects of seleno-cystine (CySe)2, glutathione (GSH), Se(IV) [as SeO2] and Se(VI) [as (NH4)2SeO4] on Th(IV) [as Th(CO3)2] uptake by the cells, Saccharomyces cerevisiae, have been studied. The Th, Se, Zn, Co and Fe levels of the yeast cells were measured by instrumental neutron activation analysis. Results obtained show that the addition of Th alone to the culture medium resulting in the Th content of the cells and the Th level of the yeast slightly decreased during the incubation. The addition of Th in combination with GSH produced a higher decrease of the Th content in comparison with the single Th dosage. During the initial 48 h of the incubation the presence of Th and Se(VI) in the medium produced a decrease of the Th level of the cells in comparison with the addition of Th alone. (CySe)2 or SeO2 does not produce a regular change of the Th level of the cells. Th uptake by the yeast influenced the retention of Se in the cells. In fact, the Se levels of the cells were always significantly higher when the yeast was incubated in the medium containing Th and SeO2 or Se(VI). The enhance in the Se level of the cells rises with increasing concentrations of SeO2 in the culture medium. Th decreased the Se content of the yeast when the cells were incubated in the medium containing (CySe)2 and Th. GSH supply in combination with Th and SeO2 produced a very significant enhancement of the Se abundance in the cells in comparison with the single addition of SeO2. Se-compounds and/or Th dosages affected the Zn, Co and Fe contents of the cells. The Fe level of the yeast is below the quantitative detection limit of Fe when the cells were incubated in the medium containing Th.