Skip Navigation

This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Right arrow Disclaimer
Google Scholar
Right arrow Articles by SULTATOS, L. G.
Right arrow Articles by MURPHY, S. D.
Right arrow Search for Related Content
PubMed
Right arrow Articles by SULTATOS, L. G.
Right arrow Articles by MURPHY, S. D.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

© 1983 Oxford University Press

research-article

Kinetic Analyses of the Microsomal Biotransformation of the Phosphorothioate Insecticides Chlorpyrifos and Parathion1,2

LESTER G. SULTATOS and SHELDON D. MURPHY

Division of Toxicology, University of Texas Medical School P.O. Box 20708, Houston, TX 77025

Kinetic Analyses of the Microsomal Biotransformation of the Phosphorothioate Insecticides Chlorphyrifos and Parathion. Sultatos, L.G. and Murphy, S.D. (1983). Fundam. and Appl. Toxicol. 3:16-21. Chlorpyrifos [0,0-diethyl-0-(3,5,6-trichloro-2-pyridyl) phosphorothioate] was metabolized to chlorpyrifos oxon [0,0-diethyl-0-(3,5,6-trichloro-2-pyridyl) phosphate] and to 3,5,6-trichloro-2-pyridinol by mouse hepatic microsomes. Formation of both chlorpyrifos oxon and 3,5,6-trichloro-2-pyridinol required NADPH, and was inhibited by carbon monoxide. Kinetic analyses using direct linear plots determined the appKm's for formation of chlorpyrifos oxon and 3,5,6-trichloro-2-pyridinol to be 20.9 ± 3.3 µM and 16.1 ± 3.4 µM respectively, while the appVmax's for the same reactions were 3.9 ± 0.2 nmols/100 mg liver/min and 8.1 ± 0.3 nmols/100 mg liver/min respectively. Incubation of parathion [0,0-diethyl-0-(4-nitrophenyl) phosphorothioate] with mouse hepatic microsomes produced paraoxon [0,0-diethyl-0-(4-nitrophenyl) phosphate] and p-nitrophenol. The appKm's for the formation of paraoxon and p-nitrophenol were 29.6 ± 4.2 µM and 26.5 ± 3.8 µM respectively, with appVmax's of 5.8 ± 0.6 nmols/100 mg liver/min and 6.7 ± 0.5 nmols/100 mg liver/min, respectively. Incubation of both parathion and chlorpyrifos at various concentrations with mouse hepatic microsomes resulted in inhibition of production of paraoxon, p-nitrophenol, chlorpyrifos oxon, and 3,5,6-trichloro-2-pyridinol, which was characteristic of mixed type inhibition. This complex kinetic behavior could arise as a result of competitive interactions of parathion and chlorpyrifos with multiple forms of microsomal cytochrome P-450.


Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?




Disclaimer:
Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department.