Protection against selenite toxicity by previous administration of selenium compounds

2-month-old male rats kept on a standard laboratory diet containing 0.06 microgram Se/g dry weight were found to be more sensitive to the toxic action of selenite than female rats of corresponding age. This sex-dependent difference was not found in 20-day-old animals. Previous s.c. administration of 1 mumol of selenium in the form of sodium selenite lowered the sensitivity of male rats to the toxic effects of selenite. The protective effect of this dose persisted for 18 days. A similar protective action against the lethal effects of selenite in adult male rats was exhibited by sodium selenate, selenomethionine, and dimethylselenide, all in an amount equal to 1 mumol of selenium; pretreatment with trimethylselenonium iodide showed only an insignificant mortality decrease. Three days intake of deionized water with an addition of 0.1 or 1.0 microgram selenium/ml also protected male rats against lethal doses of selenite. Peroral pretreatment of adult females did not decrease their sensitivity to the lethal effects of selenite.