EFFECTS OF ACID, BASE, AND AMMONIUM SULFATE ON THE PROTEIN-BINDING PROPERTIES OF METHYLMERCURY IN CYTOPLASMIC PREPARATIONS FROM AVIAN LIVER AND KIDNEY

Commercial chick starter diets containing 4 ppm Hg added as mercuric chloride or 5 ppm Hg added as methylmercuric chloride were fed to chicks starting at 1 day of age and continuing for 4 wk. The intracellular and total mercury levels of liver and kidney from birds fed each diet and the effects of treatments with NaOH, with HCl, with perchloric acid, and with ammonium sulfate and of dialysis on protein-bound cytoplasmic methylmercury were determined. Livers and kidneys from chicks fed mercuric chloride contained three times more mercury than the control, whereas those from chicks fed methylmercuric chloride contained 15 times greater concentrations than controls. The microsomes and cytoplasm from chicks fed all diets contained approximately 5 and 55% of the total tissue mercury, respectively. Dialysis of kidney cytoplasm removed 50% of the total mercury. No appreciable dissociation of an ammonium sulfate-precipitated protein–mercury complex occurred when this was dissolved in water and treated with ammonium sulfate, perchloric acid, or NaOH, whereas HCl treatment dissociated 45% of the protein-bound mercury into the supernatant. When liver cytoplasm samples were made more alkaline, a greater proportion of the total mercury was found in the protein fraction. Acidification also increased the percent protein-bound mercury to a maximum at pH 1.5, followed by a linear decrease at pH levels below 1.5.