Biotransformation of Individual Pesticides: Some Examples - Pesticide Biotransformation and Disposition - page 204

Triazine Herbicides—Atrazine
Atrazine (chemical name 2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine,
CAS No. 1912-24-9) is used extensively for the control of broadleaf weeds in agri-
cultural and roadway applications. Despite its frequent presence as a well-water con-
taminant, the U.S. Environmental Protection Agency concluded it was unlikely to be
a carcinogenic hazard to humans. It is, however, recognized as an endocrine disruptor.
The metabolism of atrazine has been investigated in surrogate animals and humans.
Lang et al. (1997) concluded that CYP1A2 was primarily responsible for atrazine
metabolism in human liver and, recently, Joo et al. (2010) identified further metabo-
lites and showed that CYP1A2 and CYP3A4 were about equally responsible for atra-
zine phase I metabolism ( Figure 9.9 ).
CONCLUSIONS
It is clear from these examples that many phase I and phase II xenobiotic-metaboliz-
ing enzymes (XMEs) are involved in the metabolism of pesticides and that individual
XME isoforms are frequently involved in the metabolism of pesticides from different
chemical and use classes. Of particular interest is the integration of the role of several
phase I and/or phase II enzymes to effect the overall metabolism of a single chemi-
cal entity. The recent emphasis on human studies of pesticide metabolism is likely to
develop quickly as new risk assessment paradigms dependent upon human cell lines
are implemented.
ACKNOWLEDGMENTS
Several authors of figures were of great help in providing the originals of figures
from the Handbook of Pesticide Toxicology, 3rd edition, or otherwise of assistance with
the adaptation of figures. Drs. M. Krolski, A.G. Smith, and A.D. Wallace are gratefully
acknowledged.
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