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  • Title: A comparison of the uptake of [75Se]selenite, [75Se]selenomethionine and [35S]methionine by tissues of ewes and lambs.
    Author: Fuss CN, Godwin KO.
    Journal: Aust J Biol Sci; 1975 Jun; 28(3):239-49. PubMed ID: 1180767.
    Abstract:
    The fate of selenium, given as Na2(75)SeO3, or [75Se]selenomethionine, and of [35S]methionine administered intravenously to ewes and lambs, has been examined. The main intention was to follow the incorporation of selenium into protein in a number of tissues, including liver and kidney, and to measure the extent of that incorporation of selenoamino acid, particularly with respect to the administration of selenite. The ewes chosen were lactating ewes with lambs at foot, and the lambs were animals which had been weaned on to fodder low in selenium and were recovering from white muscle disease with selenium therapy. These two experimental situations were chosen as they offered conditions under which selenium incorporation might be considered to be maximal. Entry of isotope into milk was rapid and was greater when 75Se was given as the selenoamino acid than as selenite. In both ewes and lambs greater amounts of activity, derived from selenite, were bound to plasma proteins than to the proteins of milk. This was particularly evident in samples taken some hours after administration. This ability of the plasma to bind selenium was demonstrated by alkaline dialysis. Small, though significant amounts of selenium, derived from Na2(75)SeO3, were incorporated as selenoamino acids into the proteins of liver, kidney and pancreas, as well as into the proteins of milk and plasma. In ewes, both selenomethionine and selenocystine were identified chromatographically in enzyme digests of defatted liver and kidney. Some differences occurred in the distribution of labelled compounds in organs from lactating ewes and recovering lambs. The incorporation of selenium into protein is discussed briefly in relation to the recent findings of an association between selenium and the enzyme glutathione peroxidase. A comparison of the uptake of selenium (Se) 75 selenite, Se 75 selen omethionine and Se 75 methionine by tissues of ewes and lambs is presented. Included in the study were 3 lactating ewes with lambs at foot and 3 lambs which had been weaned on to fodder low in selenium and were recovering from white muscle disease with Se therapy. Isotope entry into milk was rapid and was greater when Se 75 was administered as selenoamino acid than as selenite. Alkaline dialysis demonstrated that greater amounts of activity derived from selenite were bound to plasma proteins than to the protein of milk, particularly in samples taken some hours after administration. Small amounts of Se 75 selenomethionine were incorporated as selenoamino acids into the proteins of liver, kidney, pancreas, milk and plasma. Selenomethionine and selenocystine were identified chromatographically in enzyme digests of defatted liver and kidney of the ewes. Some differences were seen in the distribution of labelled compounds in organs from the ewes and lambs. Recent findings of an association between selenium and glutathione peroxidase are discussed in relation to the incorporation of selenium into protein.
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