Embryotoxicity of Arsenic Trioxide and Atrazine to Japanese Medaka (Oryzias latipes), and Cytotoxicity to Human Liver Carcinoma Cells (HepG2)

Abstract

We investigated the acute toxicity of arsenic trioxide and atrazine, singly and in combination, to Japanese medaka embryos, and the cytotoxicity of these chemicals to human liver carcinoma cell lines (HepG2). Two day-old embryos were exposed to serial concentrations of arsenic, atrazine, and a mixture of the two, following a 96-hrs static renewal test protocol. The in vitro bioassay was performed by exposing HepG2 cells to arsenic and atrazine, and measuring the activity of lactate dehydrogenase using a spectrophotometer at 340 nm, after 48 hrs of incubation at 37°C and 5% CO2. Results of the embryo bioassay indicated a concentration-response relationship with respect to chemical toxicity. Upon 96 hrs of exposure, the NOAEL, LOAEL, LC50 and LC95 of arsenic were 0.07 (0.04–0.09), 0.15 (0.10–0.18), 0.23 (0.21–0.26), and 0.32 (0.28–0.41) mg/L, respectively. No significant differences (p > 0.05) in LC50 values were found between 24 and 96 hrs of exposure, indicating that arsenic is a fast acting chemical, with most acute poisoning occurring within 24 hrs of exposure. Within the range of concentrations tested, atrazine was found to be non-toxic to embryos, even at its maximum solubility of 200 mg/L in 2% DMSO. The mixture of arsenic with 100 mg/L atrazine resulted in a 96hrs-LC50 of 0.28 (0.26–0.31) mg/L, indicating a combined toxic effect that is simply additive or slightly antagonistic. The cytotoxicity assay yielded a LC50 value of 11.94 (8.8–15.1) mg/L for arsenic. Under the test conditions, the LC50 of atrazine was greater than 100 mg/L, and could not be computed with certainty due to its poor solubility in the test medium.