Accumulation and Retention of Mercury in the Mouse

Abstract

The distribution of Hg in the mouse after a single intravenous injection of radioactively labeled methylmercuric dicyandiamide was studied by autoradiography of sagittal whole-body sections. The isotope concentration in organs was determined by densitometric comparison with the autoradiogram of a standard isotope "staircase" attached to each section. The body distribution of Hg was more uniform when compared to that found after injection of an equal dose of Hg in inorganic form, in a previous study. Up to 24 hours after injection of the methylmercuric salt, accumulation in the renal cortex, liver, and intestines was greater than that in the rest of the body; by the 16th postinjection day, only the renal cortex and brain exceeded the body average to any marked degree. The pronounced accumulation in the brain occurred slowly: the maximum concentration was not observed until between 8 to 16 days after injection. The distribution differed from that found after inorganic Hg. In the hippocampus and especially high Hg concentration was found after the injection of the organic mercurial. The autoradiograms indicate excretion of Hg in bile and urine. The placenta was not a barrier to the passage of Hg given in methylmercuric form. Hg was found evenly distributed in the fetus in concentrations comparable to those found in maternal tissues. It was concluded, for several reasons, that the distribution of Hg was intracellular and that the methylmercuric radical was not broken down to any considerable extent.