Title: Peer Review #3 of "Developmental toxicity from exposure to various forms of mercury compounds in medaka fish (Oryzias latipes) embryos (v0.1)"
Abstract: This study examined developmental toxicity of different mercury compounds, including some used in traditional medicines.Medaka (Oryzias latipes) embryos were exposed to 0.001-10 µM concentrations of MeHg, HgCl2, α-HgS (Zhu Sha), and β-HgS (Zuotai) from stage 10 (6-7 hpf) to 10 days post fertilization (dpf).Of the forms of mercury in this study, the organic form (MeHg) proved the most toxic followed by inorganic mercury (HgCl 2 ), both producing embryo developmental toxicity.Altered phenotypes included pericardial edema with elongated or tube heart, reduction of eye pigmentation, and failure of swim bladder inflation.Both α-HgS and β-HgS were less toxic than MeHg and HgCl 2 .Total RNA was extracted from survivors 3 days after exposure to MeHg (0.1 µM), HgCl 2 (1 µM), α-HgS (10 µM), or β-HgS (10 µM) to examine toxicity-related gene expression.MeHg and HgCl 2 markedly induced metallothionein (MT) and heme oxygenase-1 (Ho-1), while α-HgS and β-HgS failed to induce either gene.Chemical forms of mercury compounds proved to be a major determinant in their developmental toxicity.