Plasma & tissue esterases are responsible for hydrolysis /of organophosphorus compounds/ to the corresponding phosphoric & phosphonic acids. However, oxidative enzymes are also involved in the metabolism of some organophosphorus compounds. /Anticholinesterase agents/
The organophosphorus anticholinesterase agents are hydrolyzed in the body by a group of enzymes known as A-esterases or paraoxonases. These enzymes are found in the plasma and liver & hydrolyze a large number of organophosphorus compounds ... by cleaving the phosphoester, anhydride, P-F, P-CN bonds. /Anticholinesterase agents/
These chemicals are detoxified by cytochrome p450 mediated monooxygenases in the liver, but some metabolites are more toxic than parent cmpd ... Metabolites usually are detected from 12 to 48 hr postexposure. /Organophosphate cmpd/
Urine was collected from two male rats 12, 24, and 48 hr after an oral dose of 50 mg/kg bw radiolabelled omethoate. The cumulative percentages of administered radiolabel excreted over the indicated times were 16, 19, and 30%. The metabolites found in a 24-hr composite urine sample by ion-exchange chromatography were: O,O-dimethylphosphoric acid (34%), unknown A (52%), O,O-dimethylphosphorothioic acid (9.5%), and unknown B (4.5%). ...In the /study on on pulmonary excretion/..., the predominant form of excreted radiolabel was unchanged parent compound (26-62%), with N-methyl-2-(methylsulfinyl)acetamide accounting for 16-36% and an O-demethylated omethoate for 4-9%. Pretreatment of animals for 14 days with unlabelled omethoate followed by a single labelled dose resulted in no significant difference from the results obtained after a single administration.
Dealkylation of omethoate was proposed to be a significant detoxification mechanism on the basis of information from assays in fly heads. Oxidative metabolism of omethoate results in the de-N-methyl derivative, which is as toxic as the parent compound although less active as a cholinesterase inhibitor. Kinetic studies indicated that the reaction between acetylcholinesterase and omethoate was irreversible and bimolecular. Omethoate was 75-100 times more potent than dimethoate in inhibiting rat brain acetylcholinesterase activity.
In long term therapy, adrenocorticoids antagonize the antiglaucoma effects of anticholinesterases (incr ocular pressure). ... Anticholinergics antagonize the miotic (antiglaucoma) & other muscarinic effects of anticholinesterases on the autonomic & central nervous systems. Tricyclic antidepressants (anticholinergic effects) antagonize the antiglaucoma (miotic) effects of anticholinesterases in glaucoma. ... Antihistamines with anticholinergic effects antagonize the miotic (antiglaucoma) & CNS effects of anticholinesterases. Anticholinesterases potentiate tranquilizing & behavioral changes induced by antihistamines. The actions of anticholinesterase agents on autonomic effector cells, & to some extent those on CNS, are antagonized by atropine, an antidote of choice. Barbiturates are potentiated by anticholinesterases. ... Dexpanthenol potentiates the effects of anticholinesterases. Fluorophosphate insecticides potentiate the effects of other anticholinesterases. /Anticholinesterases/
...To examine the therapeutic effect of combined use of obidoxime and atropine with artificial ventilation on respiratory muscle paralysis caused by omethoate poisoning... rats were exposed to 2 times the dose of LD50 omethoate and treated with atropine (10 mg/kg) to counteract cholinergic symptoms. When the rats' respiratory frequency became slower and /breathing labored/, trachea intubation and artificial ventilation was carried out. The rats in group A were continuously treated with atropine. The dose of obidoxime for Group B, C and D were 8, 15, 20 mg/kg respectively, given at the same time as artificial ventilation and 1, 2, 3 hours later. The doses of atropine was reduced to 1/3 - 2/3 of the first dose so as to maintain the rats atropinized. If the rat survival was beyond 60 minutes after withdrawal of artificial ventilation, the combined treatment was considered successful. The function of isolated phrenic diaphragm of the rats was observed with MS-302 physiological and pharmacological analysis instrument. None of the rats in Group A was successful after withdrawal from artificial ventilation and the function of phrenic diaphragm appeared poor; whereas >80% of the rats in B, C, D Group were successful after withdrawal from artificial ventilation in 3 hr and the function of phrenic diaphragm remained well. The survival rate in B, C and D groups were higher after withdrawal from artificial ventilation than that in Group A(P<0.01). The function of phrenic diaphragm in Group B, C and D were gradually decreased after ACh was added into the container. /The authors concluded that/ combined use of suitable dose of obidoxime and atropine with artificial ventilation for respiratory muscle paralysis caused by omethoate poisoning could promote the recovery of diaphragm function and reduce the death rate in poisoned rats.
来源:Hazardous Substances Data Bank (HSDB)
吸收、分配和排泄
大多数有机磷化合物能够通过皮肤、结膜、胃肠道和肺部被吸收。/有机磷化合物/
Most organophosphate compounds are ... absorbed from skin, conjunctiva, gastrointestinal tract, & lung. /Organophosphate compounds/
来源:Hazardous Substances Data Bank (HSDB)
吸收、分配和排泄
有机磷农药的皮肤吸收率可能会受到所使用溶剂的影响。
The rate of dermal absorption /of organophosphorus pesticides/ may be ... influenced by the solvent used. /Organophosphorus pesticides/
... The organophosphorus insecticides are, in contrast to the chlorinated insecticides, rapidly metabolized & excreted and are not appreciably stored in body tissues. /Organophosphorus insecticides/
来源:Hazardous Substances Data Bank (HSDB)
吸收、分配和排泄
许多有机磷杀虫剂会通过牛奶排出体外...。/有机磷杀虫剂/
Many of the organophosphorus insecticides are excreted in the milk ... . /Organophosphorus insecticides/
Rapid TiO 2 /SBA-15 synthesis from ilmenite and use in photocatalytic degradation of dimethoate under simulated solar light
作者:Ge Li、Baodong Wang、Wayne Qiang Xu、Yifan Han、Qi Sun
DOI:10.1016/j.dyepig.2018.03.058
日期:2018.8
activity and good stability during four cycles, with a dimethoatedegradation rate greater than 94%. The byproducts generated during photocatalysis were identified using gas chromatography-mass spectrometry. The photocatalytic degradation of dimethoate followed first-order kinetics. The mechanism of the photocatalytic degradation of dimethoate was investigated.