Effects of pregnancy and lactation on the serum selenium content of rats

The serum selenium content of rats was measured by means of neutron activation analysis. It was found to drop between the 12th day of pregnancy and term and to return to its original level within 2 days after delivery. Hysterectomy on the 10th day of gestation prevented this decrease. Nursing had no influence on the element level. The findings suggest that placental secretions might be involved in the control of the serum selenium content of rats during pregnancy.