Thionate versus Oxon: Comparison of Stability, Uptake, and Cell Toxicity of (14CH3O)2-Labeled Methyl Parathion and Methyl Paraoxon with SH-SY5Y Cells
2010
Bharate, Sandip B. | Prins, John M. | George, Kathleen M. | Thompson, Charles M.
The stability, hydrolysis, and uptake of the organophosphates methyl parathion and methyl paraoxon were investigated in SH-SY5Y cells. The stabilities of (14CH3O)2-methyl parathion (14C-MPS) and (14CH3O)2-methyl paraoxon (14C-MPO) at 1 μM in culture media had similar half-lives of 91.7 and 101.9 h, respectively. However, 100 μM MPO caused >95% cytotoxicity at 24 h, whereas 100 μM MPS caused 4−5% cytotoxicity at 24 h (approximately 60% cytotoxicity at 48 h). Greater radioactivity was detected inside cells treated with MPO as compared to MPS, although >80% of the total MPO uptake was primarily dimethyl phosphate (DMP). Maximum uptake was reached after 48 h of 14C-MPS or 14C-MPO exposure with total uptakes of 1.19 and 1.76 nM/106 cells for MPS and MPO, respectively. The amounts of MPS and MPO detected in the cytosol after 48 h of exposure time were 0.54 and 0.37 nM/10(6) cells, respectively.
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