Disposition and retention of mercuric chloride in mice after oral and parenteral administration

The present study compares effects of dose size on whole-body retention and relative organ distribution of 203HgCl2, after oral and intraperitoneal administration to female mice of two strains (inbred CBA/Bom and outbred Bom:NMRI). Using whole-body retention data of oral and intraperitoneal administration, an estimated "true absorption" of a single oral dose of inorganic mercury was calculated to be about 20% at two different dose levels. At the highest oral dose, a delay in fecal elimination of nonabsorbed mercury was observed, indicating a decreased peristaltic rate. The relative hepatic deposition was larger after oral than after intraperitoneal administration, presumably due to a first-pass effect, and a correspondingly lower relative renal deposition was seen. Increasing doses at both exposure routes resulted in increasing relative deposition in liver, stomach, intestines, and spleen but decreasing relative deposition in lungs and kidneys. Bom:NMRI mice deposited a larger fraction of the whole-body burden in the kidneys and a smaller fraction in the livers than did CBA/Bom mice. Comparison to a previous study with male mice (Nielsen and Andersen, 1989) demonstrates that male and female mice deposit similar fractions of their body burden in the liver, while male mice deposit significantly larger amounts of mercury in the kidneys and smaller amounts in the carcass than do female mice. Thus, the toxicokinetics of inorganic mercury in mice depend on dose size, administration route, and sex; the mouse strain is of less importance than the other factors investigated. The absorption of inorganic mercury was estimated to be about 20%, that is, twice as high as earlier estimates.