Distribution of Mercury and Selenium in Egg Components and Egg-White Proteins 1

Abstract

Summary

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 CH₃ ²⁰³HgCl and H₂ ⁷⁵SeO₃ also were given to all hens. The concentration of ²⁰³ Hg and ⁷⁵ Se in egg white 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 ²⁰³ Hg in egg white when compared with a diet containing no added Se. At the same time, the addition of Se to the diet reduced ²⁰³ Hg in the egg yolk. ⁷⁵Se was found primarily in egg yolk, but 20 ppm dietary Hg significantly decreased ⁷⁵ Se in the egg yolk and increased it in the egg whites. A significant Hg × Se interaction was observed for deposition of ⁷⁵ Se 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 ²⁰³ Hg 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 ⁷⁵ Se 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.