Bioavailability of and interactions between zinc and selenium in rats fed wheat grain intrinsically labeled with 65Zn and 75Se.

A whole-body radioassay procedure was used to assess the absorption by male rats of zinc (Zn) and selenium (Se) in wholewheat grain labeled either intrinsically or extrinsically with 65Zn and 75Se. Test meals fed to zinc-depleted and to zinc-adequate rats contained grain harvested from plants grown in nutrient solutions with varying amounts of zinc and selenium. Absorption of intrinsic 65Zn by zinc-depleted rats ranged from about 46 to 57% of the dose, and 65Zn absorption decreased as the selenium content of the grain increased. Absorption of intrinsic 65Zn by zinc-adequate rats ranged from about 21 to 26% of the dose, and 65Zn absorption was not affected by the amount of either zinc or selenium in the meal. Absorption of intrinsic 75Se ranged from about 43 to 52% of the dose in zinc-depleted rats and from about 35 to 48% of the dose in zinc-adequate rats. Absorption of intrinsic 75Se by zinc-adequate rats decreased as the zinc content of the grain increased. Relative to the absorption and retention by rats of intrinsic zinc and selenium in wholewheat grain, interactions occurred between natural forms of zinc and selenium at concentrations potentially encountered in wheat. Selenium had an antagonistic effect on zinc absorption by zinc-depleted rats, and zinc had an antagonistic effect on selenium absorption by zinc-adequate rats.