Relative nutritional availability to rats of selenium in Finnish spring wheat (Triticum aestivum L.) fertilized or sprayed with sodium selenate and in an American winter bread wheat naturally high in Se.

A Finnish national programme to fertilize crops with sodium selenate led us to compare the nutritional availability to rats of selenium in two Finnish spring wheats (Triticum aestivum L.), either fertilized or sprayed with sodium selenate, with that in an American winter bread wheat naturally high in Se. Weanling male rats were given a Se-deficient Torula yeast diet for 4 weeks followed by either continued depletion or repletion for 4 weeks with graded levels of Se as sodium selenite (standard) or wheat (test food). Plasma and liver Se levels and plasma and liver glutathione peroxidase (EC 1.11.1.9; GSH-Px) activities were used as criteria of body Se status. The availability of Se under these conditions was calculated with the point-slope technique at two dietary levels of Se (Expt 1) and with the slope-ratio method (Expt 2). In the point-slope assay, the level of dietary Se fed had a considerable effect on the apparent availability values obtained which made interpretation of the results difficult. In the slope-ratio assay, no difference in the availability of Se from the various wheats was observed when plasma or liver Se levels were used as the response criteria. The Se in the fertilized wheat was somewhat more available than that in the sprayed wheat when plasma or liver GSH-Px activities were the response criteria. Overall, availability values (%) derived by averaging all four response criteria were 86, 77 and 73 for the fertilized and sprayed Finnish wheats and the American wheat respectively (sodium selenite 100). These results show that wheat is a relatively available source of Se to rats regardless of whether its Se content is naturally high or is increased by fertilization or spraying.