Metabolism of selenium-75 in the erythrocyte of growing sheep and swine

Selenium, recognized as both a toxic and an essential dietary element to the mammalian organism, has been involved in many studies of mammalian metabolism designed to evaluate its role in biological systems. Early research with selenium was very difficult due to the complex analytical techniques necessary for the detection of elemental selenium in submicroamounts. As radioactive tracer techniques were perfected, biological research with selenium became much more simple.

One very important use of a selenium isotope (⁷⁵Se) tracer technique is the study of the incorporation of selenium into tissue proteins. Selenium-75 has been shown to be incorporated into hemoproteins, cytochrome-c, myoglobin, muscle enzymes (myosin and aldolase), and nucleoproteins (McConnell, 1963). Wright (1965) has shown that ⁷⁵Se was incorporated into the hemoglobin of the newly-formed sheep erythrocyte where it remains throughout the life of the cell. This incorporation allows for an accurate determination of erythrocyte life span in sheep. The need for an accurate determination of erythrocyte life span in nutritional and physiological studies has been discussed by Judd and Matrone (1962).

Even though much research has been conducted on selenium metabolism in tissue proteins, a very important question still remains as to how selenium is bound to these proteins.

The objectives of these studies were to reinvestigate the value of selenium-75 in estimating the life span of sheep erythrocytes; to establish its value in estimating the life span of swine erythrocytes; to identify the sites of incorporation and the type of binding of ⁷⁵se in the erythrocyte of both species; and to compare the differences in selenium utilization in the erythrocyte between these species.

In order to accomplish these goals, it was necessary to determine: (1) selenium-75 uptake of whole blood, plasma, erythrocyte, and erythrocyte wash; (2) incorporation of selenium-75 into erythrocyte hemoglobin and stroma; (3) selenium-75 uptake of liver, spleen, and bone marrow; (4) erythrocyte destruction processes in each species; and (5) presence of ⁷⁵Se-containing compounds in the globin protein.