Absorption of methylmercury compounds from rat intestine

Intestinal absorption of methylmercury complexed with non-protein sulfhydryl compounds (NPSHs) as occurs in bile was studied by means of direct injection of mercury compounds into ligated intestinal segments of rats. The extent of absorption of methylmercury-cysteinylglycine (MM-CysGly) was similar to that of methylmercury-cysteine (MM-Cys) and 1.5 times larger than that of methylmercury-glutathione (MM-GSH). This result suggested that MM-CysGly, which is recognized as a major component of methylmercury in rat bile, can be easily reabsorbed from the intestine. These results indicate that not only MM-GSH and MM-Cys but also MM-CysGly may play important roles in the intestinal reabsorption of methylmercury during its enterohepatic circulation.

When the ligated intestine was pretreated with probenecid and acivicin, the intestinal absorption of MM-GSH was depressed much more than in the case of treatment with acivicin alone. This indicates the possibility that there are at least two systems for intestinal transport of MM-GSH i.e. γ-glutamyltrans-peptidase (GGT)-dependent and -independent systems.