Influence of a standard laboratory diet containing nutritionally adequate levels of selenium on renal pathology from mercury released by experimental amalgam tattoos.

Twenty-four guinea pigs were subcutaneously implanted with 2 X 25 mg of powdered dental amalgam for between 1 and 24 months. Four animals served as controls. All animals were fed a standard diet containing 0.2 microgram/g selenium (Se). Mercury (Hg) was released from the implants at an average rate of 21.7 micrograms/d and 4.35-16.94 micrograms of Se were consumed daily in the diet. The renal Hg rose to a maximum of 263 micrograms/g at 11 months in implanted animals and 6.65 mg Hg was excreted over 2 yr. The renal proximal tubular cells of implanted animals contained visible Hg deposits in secondary lysosomes and within nuclei containing both Hg and Se. No other signs of obvious renal pathology were seen in implanted animals as compared with controls. It would seem likely that the low Se levels present within this standard laboratory diet were sufficient to protect against Hg toxicity.