title: Effect of dietary methionine on utilization of tissue selenium from dietary selenomethionine for glutathione peroxidase in the rat.
abstract: To study the effect of dietary methionine on the bioavailability of Se from selenomethionine ([Se]Met), weanling rats were first loaded with Se by feeding 0.5 mg Se as [Se]Met per kg diet of a low methionine (0.17% by analysis) torula yeast-based diet for 21 d, and then were fed an Se-deficient diet (less than 0.02 mg Se/kg) supplemented with 0, 0.4 or 0.9% methionine for 28 d. Plasma, liver and muscle Se increased 2.6-, 2.5- and 2.2-fold, respectively, during [Se]Met supplementation, and then the tissue Se declined exponentially during the Se-deficient diet period. Plasma, liver and muscle glutathione peroxidase (GSH-Px) activities decreased 43-50% during the [Se]Met supplementation period in spite of the increase in tissue Se. When these [Se]Met-loaded rats were fed the Se-deficient diet and supplemented with methionine, tissue GSH-Px activities increased significantly within 3 to 7 d, but then decreased for the remainder of the experiment. Calculation of the percentage of tissue Se present as Se in GSH-Px indicated that substantial Se from dietary [Se]Met was stored in tissues in a form different from GSH-Px when a low methionine diet was fed. These results indicate that the dietary methionine level can modulate the availability of Se from dietary [Se]Met and from stored tissue [Se]Met; the inability of stored [Se]Met to provide Se for GSH-Px synthesis over a prolonged period of time suggests that [Se]Met may not be an optimum form for Se supplementation.
authors.affiliation: Department of Nutrition and Food Science, University of Arizona, Tucson 85721.
authors.forename: I H
authors.initials: IH
authors.lastname: Waschulewski
authors.forename: R A
authors.initials: RA
authors.lastname: Sunde
mesh_terms: D000818:Animals; D001682:Biological Availability; D001835:Body Weight; D004032:Diet; D005979:Glutathione Peroxidase / Q000378:metabolism*; D008099:Liver / Q000201:enzymology; D008297:Male; D008715:Methionine / Q000172:deficiency / Q000494:pharmacology*; D009132:Muscles / Q000201:enzymology; D051381:Rats; D012643:Selenium / Q000378:metabolism*; D012645:Selenomethionine / Q000378:metabolism*
chemical_list: D012645:Selenomethionine; D008715:Methionine; D005979:Glutathione Peroxidase; D012643:Selenium