The present studies attempted to identify the mechanism for the elevated urinar excretion rate for methyl mercury (MM) previously reported in CFW Swiss mice. Strain comparisons of factors which could conceivably influence renal excretion of MM were made. The biotransformation of MM to the inorganic form did not appear to play a significant role. No significant strain differences were observed in the distribution of MM between plasma and red cells under in vivo or in vitro conditions. The percentage of total plasma MM present in the low-molecular-weight fraction did not differ statistically between the CFW and CBA J strains. Strain comparisons of total reduced nonprotein thiol concentrations in liver, kidneys, whole blood, and plasma revealed no significant strain differences. A significant strain difference in plasma oxidized glutathione (GSSG) concentrations was observed. However, plasma concentrations of reduced glutathione (GSH), the form of glutathione (GS) which interacts with MM. did not significantly vary between the strains. The rate of total glutathione (TGS) excretion in urine was approximately 2-fold higher in CFW mice than in CBA J mice. The significantly higher urinary GS excretion in CFW mice was accompanied by a 1.6-fold lower urinary γ-glutamyltranspeptidase (γ-GTP) activity in this strain.
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