Species differences in biliary excretion of methylmercury--role of non-protein sulfhydryls in bile.
Species differences in biliary excretion of methylmercury and non-protein sulfhydryls (NPSHs) were studied using male rats, mice, rabbits, guinea pigs and hamsters. EDTA was added to all mixtures used throughout the experimental procedures to prevent oxidation of NPSHs. The rates of mercury excretion into the bile of guinea pigs and rabbits after the administration of methylmercury were significantly lower than those in rats, mice and hamsters. Total NPSH concentrations in the bile of guinea pigs and rabbits analyzed by HPLC were also relatively low compared with those in the other species. These results suggested that NPSH excretion plays an important role in species differences of methylmercury excretion into bile. The chemical form of the methylmercury in the bile was analyzed by gel filtration with Sephadex G-15, and most of methylmercury in bile of all species used in the experiment was bound to low molecular weight substances. The main form of methylmercury in the bile was methylmercury-glutathione (MM-GSH) in mice and hamsters and methylmercury-cysteinylglycine (MM-CysGly) in guinea pigs. Methylmercury in the bile of mice, hamsters and guinea pigs was associated with the main component of NPSHs in bile of the respective species. In the rat bile, however, GSH accounted for a majority (80%) of NPSHs, but methylmercury was separated in two peaks on gel filtration, i.e. MM-CysGly (70%) and MM-GSH (30%). This may be explained by the higher affinity of CysGly to methylmercury than that of GSH. Our data indicate that species differences in the chemical forms of biliary methylmercury reflect the species differences in NPSH components in the bile.
Urano
T
T
Department of Public Health, School of Pharmaceutical Sciences, Kitasato University, Tokyo, Japan.
Naganuma
A
A
Imura
N
N
D000818:Animals; D001646:Bile / Q000378:metabolism*; D001659:Biliary Tract / Q000378:metabolism*; D006224:Cricetinae; D006168:Guinea Pigs; D008297:Male; D008657:Metabolic Clearance Rate; D008767:Methylmercury Compounds / Q000378:metabolism* / Q000493:pharmacokinetics; D051379:Mice; D011817:Rabbits; D051381:Rats; D013045:Species Specificity; D013438:Sulfhydryl Compounds / Q000378:metabolism* / Q000502:physiology
D008767:Methylmercury Compounds; D013438:Sulfhydryl Compounds