DIETARY EFFECTS OF SELENIUM DURING REPRODUCTION IN THE RAT (LACTATION, MILK, PREGNANCY, BIOAVAILABILITY, GLUTATHIONE PEROXIDASE)

The National Research Council (NRC) has recommended a dietary selenium (Se) concentration of 0.1 ppm for the laboratory rat. This dietary level produced maximal liver glutathione peroxidase (GSH-Px) activity in growing male rats. Similar studies were not performed in female rats during growth or reproduction. The present studies were designed to determine the following: (1) concentration of dietary Se necessary for optimum Se status in reproducing rats and offspring as assessed by tissue Se and GSH-Px activity, (2) bioavailability of organic Se relative to selenite in the maternal diet during lactation, and (3) utilization of dietary Se during lactation.;Se, however, exists in many chemical forms which are known to affect its bioavailability. In these studies bioavailability of Se was estimated using slope-ratio techniques on tissue Se and GSH-Px activities in lactating dams and nursing pups. In dams and pups, bioavailability of the organic forms, selenomethionine and Se-yeast, was greater than that of selenite. The greater availability of organic Se to the pup may be a function of the greater concentration and the molecular form of Se in milk from dams fed organic Se. Regardless of form the NRC recommendation of 0.1 ppm Se was not adequate during lactation to replete Se-depleted dams and maintain maximum GSH-Px in nursing pups.;The utilization of dietary ('75)Se was altered during lactation with a greater retention of ('75)Se in both the mammary gland and milk. Retention of ('75)Se was also influenced by the chemical form administered. Retention of ('75)Se-selenomethionine was greater than that of ('75)Se-selenite, especially in nursing pups. This enhanced retention of ('75)Se-selenomethionine by the pup did not appear to result from a greater concentration of ('75)Se in milk but may be related to a greater Se concentration in certain proteins of rat milk.;The results of these studies demonstrated that the NRC recommendation of 0.1 ppm Se does not provide adequate Se for reproducing rats. During reproduction at least 0.2 ppm Se was required (as selenite) to maintain maternal tissue Se and GSH-Px activities and milk Se concentrations that resulted in the greatest GSH-Px activity in the nursing pup.