Passage of selenium through the mammary glands of the white rat and the distribution of selenium in the milk proteins after subcutaneous injection of sodium selenate.

One of the pathways by which selenium may be eliminated from the animal body other than through the kidney, gastrointestinal tract, and lung is through the mammary glands into the milk of lactating animals. This has been shown by several investigators to take place in certain domestic animals. Dudley (1) found 0.02 to 3.00 parts per million of selenium in the milk of selenized cows. Smith et al. (2) reported in an extensive survey that milk from cows grazing in seleniferous areas contains 16 to 127 y of selenium per 100 cc. Moxon (3) observed that selenium was carried in the milk of selenized animals to such an extent that nursing calves often showed all the prominent symptoms of “alkali” disease. Organoselenium as obtained from seleniferous grains (Franke and Potter (4) ) and inorganic selenium, when administered to experimental animals, have been shown to pass into the proteins of liver’ (Westfall and Smith (5) ), muscle,’ the plasma fractions’ (Westfall and Smith (5)), and hemog1obin.l In view of the fact that there is a certain fixation of selenium in tissue proteins, the question may be raised whether selenium of the milk exists in the milk proteins and, if so, in what protein fractions. In order to obtain information about the nature of selenium in the milk of selenium-injected white rats, various experiment,s were carried out. The experiment.s reported here were carried out with the radioactive isotope of selenium. With the use of radioselenium which has the advantages of a ha.lf life of 50 days with a specificy-ray emission of 0.05 and 0.21 m.e.v., microdeterminations of selenium were made with far greater accuracy than are possible by any known chemical analytical procedure. The extreme sensitivity of the method mxde possible quantitative detections of traces of selenium.