In Vitro Characterization of the Intestinal Absorption of Methylmercury using a Caco-2 Cell Model

Methylmercury (CH3Hg) is one of the forms of mercury found in food, particularly in seafood. Exposure to CH3Hg is associated with neurotoxic effects during development. In addition, methylmercury has been classified by the International Agency for Research on Cancer as a possible human carcinogen. Although the diet is known to be the main source of exposure, few studies have characterized the mechanisms involved in the absorption of this contaminant. The present study examines the absorption process using the Caco-2 cell line as a model of the intestinal epithelium. The results indicate that transport across the intestinal cell monolayer in an absorptive direction occurs mainly through passive transcellular diffusion. This mechanism coexists with carrier-mediated transcellular transport, which has an active component. The participation of H+- and Na+-dependent transport was observed. Inhibition tests point to the possible participation of amino acid transporters (B-0,B-+ system, L system, and/or y(+)L system) and organic anion transporters (OATs). Our study suggests the participation in CH3Hg absorption of transporters that have already been identified as being responsible for the transport of this species in other systems, although further studies are needed to confirm their participation in intestinal absorption. It should be noted that CH3Hg experiences important cellular acumulation (48-78%). Considering the toxic nature of this contaminant, this fact could affect intestinal epithelium function.