Distribution of Mercury and Selenium in Egg Components and Egg-White Proteins

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Abstract
Methylmercuric chloride (Hg) at 20 ppm and sodium selenite (Se) at 8 ppm were fed, separately and in combination, to laying hens. Oral doses of CH3203HgCl and H275SeO3 also were given to all hens. The concentration of 203Hg and 75Se in egg whites and egg yolk and the distribution of the radioisotopes among proteins of egg white were determined. The highest concentrations of 203Hg were observed in egg white. The 8 ppm of dietary Se significantly increased the concentrations of 203Hg in egg white when compared with a diet containing no added Se. At the same time, the addition of Se to the diet reduced 203Hg in the egg yolk. 75Se was found primarily in egg yolk, but 20 ppm dietary Hg significantly decreased 75Se in the egg yolk and increased it in the egg whites. A significant Hg .times. Se interaction was observed for deposition of 75Se in egg white. When dietary Hg was fed separately from dietary Se, 75Se deposition was increased in the egg whites. More than 97% of the total 203Hg in egg white was associated with ovalbumin. Similarly, total Hg was found in greatest quantities in ovalbumin, irrespective of the addition of dietary Hg or Se. The largest proportion of total 75Se dose and the highest concentration of total Se per unit of protein occurred in globulin, especially when 8 ppm Se were fed. The data illustrate preferential binding of Hg by ovalbumin and of Se by globulin as compared with other major proteins of egg white.