Enzymes Involved in the Metabolism of Organophosphorus, Carbamate and Pyrethroid Insecticides

Schoknecht, Ute; Otto, Dieter

doi:10.1007/978-3-642-69793-7_2

Cited by 5 publications

(6 citation statements)

References 262 publications

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“…Oxidative desulfuration of phosphorothionates by mixed-function oxidases to generate activated oxons that subsequently phosphorylate 'Besterase' is a well-documented event. 15 Our earlier studies with these insecticides have shown that they are less neurotoxic than monocrotophos in rat, as assessed by brain acetyl cholinesterase (AChE) inhibition. 3 Based on the metabolic findings, it was likely that carboxylesterase hydrolysis of the insecticides provided a major route of Correlation coefficient values between GSH and GST after treatment by the two compounds indicated a high positive correlation, i.e.…”

Section: Discussionmentioning

confidence: 99%

Alterations in hepatic detoxifying enzymes induced by new organophosphorus insecticides following subchronic exposure in rats

Mahboob¹,

Siddiqui²

2001

J of Applied Toxicology

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The present study examined the structure-toxicity relationship of two novel phosphorothionates, a methyl ester (RPR-II) and an ethyl ester (RPR-V), with regard to their interaction with certain biochemical indices in rat. Male rats were treated orally with 10% (low), 20% (medium) and 30% (high) doses of the two compounds (14, 28 and 42 microg kg(-1) day (-1) of RPR-II and 33, 66 and 99 microg kg(-1) day(-1) of RPR-V) daily for 90 days. The activity of hepatic glutathione S-transferase (GST) and UDP-glucuronyl transferase (UDPGT) and the level of glutathione (GSH) were estimated at 0, 45 and 90 days of treatment as well as 28 days after cessation of treatment. RPR-II caused statistically significant depletion of GSH after 45 and 90 days of treatment at the high dose, whereas RPR-V depleted GSH only after 90 days at the high dose. RPR-II inhibited GST after 45 and 90 days at medium and high doses, whereas RPR-V caused inhibition of GST after 45 and 90 days only at the high dose. Significantly, UDPGT activity was increased only by the high dose of RPR-II after 90 days. However, a dose and time-dependent increase in UDPGT activity was observed at all three doses of RPR-V after 45 and 90 days. There was no modulation in any of the three indices at low doses of the two organophosphorus insecticides. The withdrawal study revealed that induced changes in hepatic parameters were reversible 28 days after cessation of treatment. The results indicated that the two insecticides had different potential to modulate hepatic GST, UDPGT and GSH due to subchronic exposure and that these metabolic alterations are quite reversible after withdrawal of treatment.

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Section: Discussionmentioning

confidence: 99%

Alterations in hepatic detoxifying enzymes induced by new organophosphorus insecticides following subchronic exposure in rats

Mahboob¹,

Siddiqui²

2001

J of Applied Toxicology

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“…Oxidative desulfuration of phosphorothionates by M O to generate activated oxons that subsequently phosphorylate 'B-esterases' is a well documented event. 13 The novel organophosphorus insecticide studied here is a thionate and shows strong NADPH-dependent inhibition of a-NaE. The time-dependent inhibition of carboxylesterase activity thus provides an indication of the formation of PRP-5 oxon in the rat and the quail.…”

Section: Discussionmentioning

confidence: 83%

In-vitro Metabolism of a Novel Monocrotophos Derivative by Rat and Japanese Quail

Siddiqui

Walker

1996

Pestic. Sci.

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NADPH-dependent inhibition of hepatic microsomal carboxylesterase by a derivative of monocrotophos (coded as RPR-5) was studied in rat and Japanese quail as a measure of monooxygenase-catalysed activation of RPR-5. There was NADPH-dependent inhibition of hepatic microsomal a-naphthyl acetate esterase (carboxylesterase) both in rat and quail, indicating monooxygenasecatalysed formation of an oxon that subsequently phosphorylated a-NaE. The pattern of in-vitro metabolism of 14C-labelled RPR-5 by 11 OOOg supernatant (1 1-S), microsomes and 105000g supernatant (105-S) fractions of rat and quail livers suggested the involvement of microsomal monooxygenases and carboxylesterases. A radiolabelled metabolite (M2) was tentatively identified as an acid produced by carboxyl esterase attack. In rat, metabolism by microsomal and cytosolic (105-S) carboxylesterases appeared to predominate with relatively little oxidative metabolism. In quail, putative microsomal carboxylesterase hydrolysis of RPR-5 was much lower than in the rat with almost neglible hydrolysis by cytosolic fractions. Also, production of M, by quail microsomes was substantially reduced after addition of NADPH, suggesting inhibition of a carboxyl esterase by the oxon of RPR-5. Differences in this detoxification of RPR-5 between rat and quail may be an important factor in determining selective toxicity and the results underline the importance of relating metabolism to toxicity when selecting animal models for toxicity testing.

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“…Such results do not exclude participation of esterases, because PBO is also known to be an esterases blocker (Gunning et al 1998). However, other scientific papers emphasis that PBO is mainly an oxidative enzymes blocker and only slightly inhibits esterases (Schoknecht and Otto 1989;Malinowski 2003). In light of this, our results showing high synergism between deltamethrin and PBO prove that not only oxidases, but also some esterases take part in the pyrethroid detoxificatoion.…”

Section: Discussionmentioning

confidence: 97%

Susceptibility Level of the Pollen Beetle (Meligethes Aeneus F.) to Selected Pyrethroids in Poland, and Resistance Mechanisms of the Pest to Deltamethrin

Zamojska

Wegorek

Mrowczynski

2013

Journal of Plant Protection Research

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Pollen beetle susceptibility level to different insecticides has been investigated in Poland for several years. So far, high resistance to many of the insecticides’ active substances has been found. The work presents the current status of the pollen beetle susceptibility level to deltamethrin and beta-cyfluthrin, pointing to the beetle’s medium, high or very high resistance to both active substances. Also, pollen beetle resistance mechanisms to deltamethrin were investigated. Research, conducted with the use of oxidases, esterases and glutathione transferases blockers, showed that all three enzymes groups are involved in the pollen beetle resistance mechanisms to deltamethrin. The main role was played by oxidases and to a lower degree: esterases and glutathione transferases, respectively.

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Enzymes Involved in the Metabolism of Organophosphorus, Carbamate and Pyrethroid Insecticides

Cited by 5 publications

References 262 publications

Alterations in hepatic detoxifying enzymes induced by new organophosphorus insecticides following subchronic exposure in rats

Alterations in hepatic detoxifying enzymes induced by new organophosphorus insecticides following subchronic exposure in rats

In-vitro Metabolism of a Novel Monocrotophos Derivative by Rat and Japanese Quail

Susceptibility Level of the Pollen Beetle (Meligethes Aeneus F.) to Selected Pyrethroids in Poland, and Resistance Mechanisms of the Pest to Deltamethrin

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