Submitted to: Journal of Federation of American Societies for Experimental Biology
Publication Type: Abstract Only
Publication Acceptance Date: April 20, 2002
Publication Date: N/A
Technical Abstract: Studies of selenium (Se) physiology have been mainly directed at elucidating the functions of selenocysteine containing selenoproteins. Little attention has been given to the occurrence, distribution or functions of low molecular weight selenomolecules. We examined the distributions of selenoproteins and low molecular weight selenomolecules in tissues isolated from a weanling female pig fed a low-Se torula yeast diet for 8 d, supplemented orally with 2.5 mCi [75-Se]selenite and equilibrated 6 d. Phosphorimaging of 75-Se labeled species after SDS-PAGE of plasma, erythrocytes, lymphocytes, platelets, brain, liver, lung, heart, muscle, spleen and kidneys indicated selenoproteins with molecular weights of approx. 77, 53, 42, 23, 15, 10, and 8 kD in tissue specific distributions, but did not reveal any low molecular weight selenomolecules. When tissue homogenates were centrifuged through 5 kD molecular weight cut off ultra- filtration membranes, filtrates from brain contained 20% of the total 75-Se while in other tissues this fraction contained 2% or less. Because no low molecular weight 75-Se species were observed in any gel lanes following SDS-PAGE, we speculate the selenomolecules were small enough to diffuse out of gels during fixation and staining. Low molecular weight selenomolecules could have brain specific functions or may reflect adducts involved in highly specific Se sequestration and retention demonstrated by mammalian brain tissues.