Selenourea and colloidal selenium: their role in radioprotection and radiosensitization of enzyme and cellular systems.

The effect of selenourea and of colloidal selenium on dilute aqueous solutions of the enzyme yeast alcoholdehydrogenase and on suspensions of E. coli B/r has been studied. Selenourea usually appears to protect meanwhile colloidal selenium radiosensitizes. The results are considered in terms of chemical stability of selenourea and of its free radical reactivity.