Subcellular distribution of mercury in the rat kidney cortex after exposure to mercuric chloride

Abstract

The subcellular distribution of mercury in the rat kidney cortex was studied in tissue fractionation experiments after a single subcutaneous injection of radioactive mercuric chloride ( 203HgCl 2) or following exposure to mercuric chloride in the drinking water (15 mg Hg/liter) for 2, 6, and 10 months. Subcellular fractions were isolated from cortical homogenates by differential centrifugation and assayed for mercury, protein, and acid phosphatase. Seventy-two hours after the injection of 20 μg 203Hg, (specific activity 0.8 mCi/mg Hg), 37% had accumulated in the kidneys. The subcellular distributions of mercury 72 hr after a single injection and after 2 months of exposure via the drinking water were similar, although a significant increase in the relative specific mercury content in the lysosomal fraction was observed after 2 months. The highest concentration of mercury was seen in the supernatant in both groups. After 6 and 10 months of exposure there was an accumulation of mercury in the lysosomal fraction, the relative specific activities being 2.38 and 1.98, respectively. Proteinuria was more pronounced in mercury-treated rats than in controls. In addition, there was a statistically significant increase in kidney weight with increasing time of mercury exposure. The present study demonstrates that mercury becomes concentrated in kidney lysosomes in rats with chronic mercury intoxication, whereas there is no enrichment of mercury in the kidney lysosomes after short-term exposure. A positive correlation between proteinuria and the presence of mercury in renal lysosomes is suggested.