Metabolic models for methyl and inorganic mercury.

We have derived two different models representing the metabolic behavior of both inorganic and methyl mercury. Simple three- and four-compartment models fit the short-term data very well. However, it was necessary to add long-term compartments to the data so the model would be in keeping with the long-term data as observed in Reference Man, ICRP Publication 23 and in industrial experience (ICRP75). One concept not used in our models is biotransformation. It has been established that in the rat methyl mercury undergoes a biotransformation that cleaves the carbon-methyl bond and releases inorganic mercury (No 70; No 71). However, we were unable to find any human data. Since methylation of inorganic mercury is known to occur, it might be expected that methylation would occur in mammals. Rowland et al. have shown that the contents of the rat cecum can synthesize methyl mercury from mercuric chloride (Row 77). Furthermore, they also showed that bacteria from human feces can cause methylation. Clearly, a model incorporating biotransformation would be useful but it must await further experimental evidence.