Parathion (E-605) 
~  0,0-Diethyl O0-p-nitrophenyl phosphorothioate (Parathion) 
0,0-Dimethyl O-p-nitrophenyl phosphorothioate (Methyl Parathion) 
Investigations have shown that the hydrolysis of parathion to para- 
oxon by liver was common to many animals: turtle (Pseudomys sp.), brook 
trout, brown trout, mud puppy, frog (Rana pipiens), pigeon, rabbit (Dutch 
belted), guinea pig, toad (Bufo sp.) mouse, rat and pig (Yorkshire) (1176). 
Application of parathion and paraoxon to the skin of man, cat, rabbit, 
and rat showed that only the paraoxon was hydrolyzed (489, 491, 736). In 
man, the only metabolite identified was p-nitrophenol in urine (507, 873). 
More extensive studies with labeled parathion conducted with rats showed 
that highest levels of radioactivity appeared in the salivary glands and 
cervical brown fat. Liver, kidney, and adipose tissues also showed high 
radioactivity. Labeled material was excreted mainly by the kidneys and 
not in bile (490). 
Other studies with rats have shown that parathion metabolism pro- 
ceeded via de-alkylation as well as paraoxon. Mono- and di-methyl phos- 
phate, dimethyl phosphorothioate, thiophosphate, inorganic phosphate and 
p-nitrophenol were also observed (13, 181, 350, 369, 499, 500, 538, 843, 
1016, 1017, 1021, 1022, 1063, 1443). Similar results were obtained when 
methyl parathion was fed to male Swiss mice (682). 
When parathion was incubated with bovine rumen fluid, paraoxon, amino 
parathion, and amino paraoxon were produced along with diethyl phosphoric 
and phosphorothioic acids (10, 299, 1125). In the case of nonruminating 
mammals, p-nitrophenol was excreted in the urine (401, 526). In cattle, 
however, conjugated p-aminophenol was excreted in the urine, probably the 
result of the ability of rumen organisms to reduce parathion to amino 
parathion. 
Studies have also shown that mammalian blood was capable of hydrolyzing 
parathion (412, 1078). 
Liver homogenates from several species of mammals, birds and fish were 
used to study nitroreductase activity. A comparison of the data showed that 
enzymatic activity varied between classes and among species within a given 
class of animals. Although reduction of the nitro group to the amino group 
probably proceeded via the nitroso and hydroxylamino derivatives, the 
presence of neither one was detected. Species tested included: rat, mouse, 
guinea pig, chicken, English sparrows, bullhead, sucker, flounder, sculpin, 
large mouth bass, sunfish, bluegill, alewife. Distribution of nitro- 
reductase in rats varied among tissues: liver> kidney> spleen> heart> 
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