Fish consumption is considered to be a major human exposure route for mercury (Hg), but assessing the actual Hg bioavailability from consumed fish is challenging. In this study, we conducted both in vivo bioavailability (using a mouse model) and in vitro bioaccessibility (using various gastrointestinal digestion methods) assessments of Hg from consumed fish. Lyophilized fish muscles which already absorbed Hg through natural incorporation were introduced to mice by active feeding. Assimilation efficiency (AE) was measured as a short-term kinetic parameter, while a 7-day accumulation of Hg in mice blood, liver and kidney was determined. The AEs of Hg in mice ranged between 82 and 96% and showed a positive relationship with MeHg in fish independent of the fish species. For long-term bioavailability tests in which the Hg retention in organs was measured after a 7-day exposure, most Hg was found to be accumulated in liver and kidney, resulting in a strong correlation between Hg dosage and accumulation in mice organs. The long-term absolute bioavailability of mice was comparable between the liver and kidney, but much lower in the blood. The calculated absolute total Hg bioavailability ranged between 38% and 99% and decreased as the Hg dosage increased. Results of bioaccessibility tests varied considerably among different methods, illustrating that there were limitations for the in vitro bioaccessibility assay to predict the digestive dynamics of Hg in mammalian gastrointestinal tract. Our study strongly demonstrated the expediency of direct determination of Hg bioavailability, but more bioaccessibility assessments should be explored and optimized as an alternative to traditional animal experimentation.
Keywords: Assimilation efficiency; Bioaccessibility; Bioavailability; Mercury; Seafood.
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