Metabolism of methylmercury in rabbits and hamsters

The metabolism of 203Hg-labeled methylmercury chloride (MeHg) has been studied in rabbits and hamsters. Rabbits were administered 1.6 mumols MeHgCl/kg bw intravenously, and hamsters 40 mumols/kg bw orally. Urine and feces were collected daily and groups of four animals killed after 1 h, 1 d, or 7 d. The concentration of 203Hg in blood, liver, kidney, spleen, lung, heart, and brain was determined by gamma counting. In both animal species, the clearance of 203Hg in the brain was slower than in other tissues. In the rabbits the brain 203Hg concentration increased during the whole experimental period. Rabbits excreted 203Hg primarily in feces (about 20% of the dose within 1 wk), and much less in urine (less than 2%). In contrast, hamsters very efficiently excreted 203Hg in urine (50% in 1 wk). The fecal excretion was similar to that of the rabbits. Separation of inorganic Hg and MeHg in urine from hamsters by ion exchange chromatography showed that about 90% of the urinary 203Hg was excreted as MeHg. These findings show that rabbits and hamsters are interesting experimental animal systems for studying the metabolism of MeHg.