Determination of the half life of fenthion in New Zealand white rabbits using three routes of administration

Emteres, Ramadan; Abdelghani, A. A.

doi:10.1080/03601238509372496

Cited by 4 publications

(1 citation statement)

References 7 publications

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“…In the case of V, the synthetic porphyrin predominantly oxidized the C-S sulfur as recently reported for aromatic and aliphatic sulfides, 30) followed by ester cleavage and desulfuration to form Vd and Ve. Although it was not clear which site, PϭS or C-S sulfur, was more susceptible to oxidation, significant amounts of oxon and its sulfone in addition to Va, Vb and Ve and hydrolytic products were detected in rat 31) and rabbit 32) metabolism studies. These results indicated that the electronic character primarily controlled the porphyrin-mediated oxidation and the absence of steric constraint caused the different reac- tion profiles from P450-catalyzed metabolism.…”

Section: Discussionmentioning

confidence: 99%

Oxidative Activation and Degradation of Organophosphorus Pesticides Mediated by Iron Porphyrins

Fujisawa

Katagi

2005

J. Pestic. Sci.

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Oxidative metabolism catalyzed by cytochrome P450 enzymes (P450) is one of the most important degradative pathways for xenobiotics including pesticides. Many types of reactions such as hydroxylation of alkyl and aromatic carbons, dealkylation via stepwise oxidation, epoxidation of alkene and oxidation at nitrogen and sulfur atoms are known to be catalyzed. [1][2][3] The atomic oxygen originating from molecular oxygen is bound to iron of the protoporphyrin IX moiety in P450 and its transfer to a substrate proceeds in the presence of NADPH.The Fe (valence, IV; spin state, Sϭ1) porphyrin-oxygen cation radical has been strongly suggested as the prosthetic moiety in an active state by extensive theoretical studies and the triplet oxene is considered to be the most appropriate model. 4) In order to examine the mode of action of P450-catalyzed oxidation at a molecular level, Keserü et al. have applied computational methods including molecular orbital (MO) calculations and molecular dynamic simulations to the carbofuran-P450cam complex utilizing the three-dimensional structure of the enzyme. 5) Either hydrogen bonding or steric constraint imposed by the polypeptide backbone was found to highly control the oxidation of carbofuran near the active site and the major metabolic hydroxylation at the 3-position was correctly elucidated. Another approach has been to use synthetic metalloporphyrins as a model of P450 especially in the field of drug metabolism. 3,6,7) The various types of electrondeficient iron porphyrins have been recently synthesized to increase oxidative reactivity and moreover, the introduction of bulky phenyl groups at meso-positions of the porphyrin ring has successfully hindered the unfavorable formation of the moxo dimer in the catalytic oxidation. 8) The co-existence of an oxidant such as hydrogen peroxide in organic solvent was found to well simulate the P450-catalyzed reactions of many chemicals including several carbamate insecticides. 3,9) The oxidative desulfuration of phosphorothioate pesticides to form the corresponding oxon or S-oxidation of the alkylthio group to sulfoxide and sulfone is a well-known metabolic reaction catalyzed by P450. 10) These reactions have been extensively examined for the various radiolabels of parathion, and phosphoxathiirane is proposed to be a key intermediate which is activated to the oxon with a release of an elemental sulfur or reacts with water to form the corresponding phenol. 11) Oxidative desulfuration through this intermediate was found to be feasible in a theoretical analysis using a reaction coordinate method in MO calculations of model compounds. 12) In order to examine the applicability of synthetic iron porphyrins as a biomimetic model of P450, we carried out the oxidation of several organophosphorus pesticides using three types of iron porphyrins. The reactivity and product distribution were also examined with the aid of MNDO-J. Pestic. Sci., 30(2), 103-110 (2005) * To whom correspondence should be addressed. E-mail: fujisawat1@sc.sumitomo-chem.co.jp ©...

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Section: Discussionmentioning

confidence: 99%

Oxidative Activation and Degradation of Organophosphorus Pesticides Mediated by Iron Porphyrins

Fujisawa

Katagi

2005

J. Pestic. Sci.

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Prolonged organophosphate toxicity in a twenty-six-month-old child

Borowitz

1988

The Journal of Pediatrics

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Selected Neurotoxins

Nafe

1988

Veterinary Clinics of North America: Small Animal Practice

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The small animal practitioner is faced with an infinite number of potential toxins in our modern environment. Unapproved usage of drugs and insecticides requires the practitioner to keep informed about the development of new toxic syndromes. Recreational drug toxicosis in animals is still seen with some frequency in clinical practice and should not be overlooked, even when the owner denies the possible exposure. In this article, we have discussed a few of the more common and newer neurotoxicities seen in clinical practice today. Neurologic toxicities are complex, but treatment can be rewarding if early diagnosis is made and aggressive therapy is instituted. The practitioner will find it worthwhile to establish contact with a toxicologist or poison information center for additional support when necessary.

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Determination of the half life of fenthion in New Zealand white rabbits using three routes of administration

Cited by 4 publications

References 7 publications

Oxidative Activation and Degradation of Organophosphorus Pesticides Mediated by Iron Porphyrins

Oxidative Activation and Degradation of Organophosphorus Pesticides Mediated by Iron Porphyrins

Prolonged organophosphate toxicity in a twenty-six-month-old child

Selected Neurotoxins

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