Parathion labeled

Studies have found that methyl parathion degrades more rapidly in anaerobic soil than in aerobic soils (Adhya et al. 1981, 1987 Brahmaprakash et al. 1987). An average half-life of 64 days was determined for nonflooded (aerobic) soils compared to an average half-life of 7 days in flooded (anaerobic) soils (Adhya et al. 1987). In experiments with " C-labeled methyl parathion, 35% of the labeled compound was recovered from nonflooded soil after 28 days, compared with 9% recovered from flooded soil (Brahmaprakash et al. 1987). 

Results from other studies support the rapid degradation of methyl parathion in soils with a high water (i.e., low oxygen) content (Adhya et al. 1981, 1987 Brahmaprakash et al. 1987). Experiments in flooded and nonflooded soils showed that the redox potential affected both the rate of degradation and the transformation products of methyl parathion (Adhya et al. 1981, 1987). Transformation to volatile products was suggested by Brahmaprakash et al. (1987) as the reason that significant amounts of " C from labeled methyl parathion could not be accounted for, especially in flooded soils. 

The first application of immunologically based technology to pesticides was not reported until 1970, when Centeno and Johnson developed antibodies that selectively bound malathion. A few years later, radioimmunoassays were developed for aldrin and dieldrin and for parathion. In 1972, Engvall and Perlman introduced the use of enzymes as labels for immunoassay and launched the term enzyme-linked... 

Fig. 16.37 Formation of parathion hydrolysis product (fraction of initial label appearing in the aqueous extract) in remoistened Gilat soil after application of 10-160p,g parathion per g dry soil. Plotted points are means of three replicates standard error. Continuous curves represent model simulations. Reprinted from Nelson LM, Yaron B, Nye PH (1982) Biologically-induced hydrolysis of parathion in soil. Soil Biol Biochem 14 223-227. Copyright 1982 with permission of Elsevier...

Figure 5. SDS-PAGE of a reconstituted moiwoxygermse system from rat liver that had been labeled with 5 by incubation with parathion. The incubation procedures were essentially as described in Figure 4 (20).

Figure 7. Elution profile of protein, radioactivity, and thiocyanate from a Sepha-dex G-25 column of a reconstituted monooxygenase system from rat liver that had been incubated with [ 5] parathion followed by incubation with cyanide. The incubation conditions and analytical procedures were as described in Figure 7 except that the labeled protein was incubated with lOmM sodium cyanide for 3 h at room temperature prior to being applied to the Sephadex column (20).

DOT CLASSIFICATION 6.1 Label Poison SAFETY PROFILE Poison by inhalation, ingestion, skin contact, subcutaneous, intravenous, and intraperitoneal routes. Fatal poisoning can result from skin or eye contact after very brief exposure to concentrated solution. Experimental teratogenic and reproductive effects. Questionable carcinogen. Human mutation data reported. A cholinesterase inhibitor type of insecticide. When heated to decomposition it emits very toxic fumes of NOx, POx, and SOx. See also PARATHION. 

Incubation of liver microsomes with [ S]parathion results in radiolabeling of the protein but no radiolabeling occurs when the parathion ethyl groups are labeled with - . Ninety percent of the S-label, bound covalently to the microsomal proteins is immunoprecipitated... 

The mass balance approach was used to develop an in vivo animal model for skin penetration of topically applied dmgs in hairless rats (Simonsen et al., 2002). Two dmgs, C-sahcylic acid and C-butyl salicylate were topically applied for the assessment of the model. Rapid and differentiated percutaneous absorption of both compounds was indicated by urinary excretion data. Total mass balance on the applied radioactivity was performed, and 90% recovery was achieved. Carver and Riviere (1989) conducted an extensive mass balance study with " C-labeled xeno-biotics after topical and intravenous administration to pigs. These authors reported that dermal absorption of C-benzoic acid, caffeine, malathion, parathion, progesterone, and testosterone was 25.7, 11.8, 5.2, 6.7, 16.2, and 8.8%, respectively, following topical administration to pigs. 

Finite, nonoccluded doses (600 ug) of [ C]labeled parathion and carbaryl were absorbed through the back skii of j ult males at the rate of 0.33 and 0.18 ug hr cm of skin. This rate was sufficient to absorb 57% of the applied dose of parathion and carbaryl over a period of 168 hr. A computer program, Nonlin, was used to calculate the plasma rate constants for simultaneous absorption-elimi ijation. A finite, nonoccluded dose (570 ug) of [ thiodicarb was slowly absorbed (0.042 to 0.27 ug hr cm of skin) and acted as if it were an infinite dose applied to the skin. Approximately 22% of the applied dose was absorbed over a period of 168 hr. 

The total amount of [ C]labeled parathion, carbaryl, and thiodicarb equivalents present in ug and percentage of dose is given in Table II. Carbaryl, parathion, and thiodicarb reached plateau values of 35, 17, and 7 ug, respectively, per treated area of skin. 

Simultaneous Absorption and Elimination in Plasma. The ty e-concen-tration curves for the absorption and elimination of [ C]labeled parathion, carbaryl, and thiodicarb equivalents in plasma of adult rats are giv in Figure 8 and the pharmacokinetic constants in Table III. The [ C]equivalents were found in blood shortly after the application of the dose and reached maximum concentrations in plasma in 2.5 to 12 hr. Carbaryl and paraty on [ C]equivalents were eliminated during the study, while [ C]thiodicarb equivalents... 

Figure 4. Loss of surface and penetrated [ C] labeled parathion and carbaryl equivalents from skin of adult rats. Keys , carbaryl, adult male , parathion, adult male 0> parathion, adult female. (Reproduced with permission from Ref. 9. Copyright 1984, Academic Press.)...

TABLE II. [ C]Labeled Parathion, Carbaryl, and Thiodicarb Equivalents in Treated Skin in ug and % of Dose ... 

Absorption Rates. The skin absorption rates for [ C]labeled para-thion, carbaryl, thiodicarb in adult rats are given in Table IV. Female rats absorbed parathion faster than males as indicated in this Table when either the t 1/2 for plasma elimination or for skin loss was used. In males and females, the t 1/2 for skin loss gave higher absorption rates than the t 1/2 for elimination from plasma. This difference is believed to be produced by evaporative losses of parathion from skin. Carbaryl was absorbed at a slower rate than parathion in males when the t 1/2 for plasma elimination or the t 1/2 for skin loss was used. Dijfer ces in the absorption rate for carbaryl (0.18 vs 0.44 ug hr cm maybe caused by evaporation. In the case of thiodicarb, t 1/2 for skin loss (a and g phase) was used to determine the rate of absorption because steady state plasma concentrations prevented the calculation of the t 1/2 for elimination of thiodicarb from plasma. 

The following metabolites were identified in a soil-oat system paraoxon, aminoparathion, /7-nitrophenol and p-aminophenol (Lichtenstein, 1980 Lichtenstein et al., 1982). Mick and Dahm (1970) reported 1i)at Rhizobium sp. converted 85% C-labeled parathion to aminoparathion in one day and 10% diethylphosphorothioic acid. 

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