Role of reactive oxygen metabolites in organophosphate-bidrin-induced renal tubular cytotoxicity.
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Due to low toxicity to nontarget species and rapid degradation after its application, organophosphate (OP) remains a widely used class of pesticide. Suicidal or accidental overdose of OP can result in acute tubular necrosis. Experimental evidence shows little correlation between the renal tubular necrosis and the degree of OP-induced acetylcholinesterase inhibition, the main mechanism of OP's toxicity, suggesting the involvement of alternate mechanisms. Since reactive oxygen species (ROS) are known mediators of many toxin-induced renal injuries, this study was conducted to investigate whether ROS play a role in Bidrin (BD)-induced renal tubular epithelial cell (LLC-PK1) toxicity. BD is an OP insecticide formulation with dicrotophos as the active ingredient. LLC-PK1 cell death, determined by lactate dehydrogenase (LDH) release (% of total), rose concentration- and time-dependently after exposure of the cells to 1000, 1250, 1500, 1750, and 2000 ppm of BD for 6, 12, 24, and 48 h. Antioxidants 2-methylaminochroman (2-MAC; 0.3 to 2.5 microM) and desferrioxamine (DFO; 0.25 to 2 mM) reduced cell damage induced by 1250 ppm of BD over a 24-h incubation in a concentration-related manner. The greatest reductions in % LDH were produced by DFO 2 mM and 2-MAC 2.5 microM, both significantly lower than BD alone. H2O2 levels (micromol/mg protein per h) were significantly elevated after exposure to 1250 ppm of BD. Significantly increased malondialdehyde formation (nmol/mg protein) compared with control was also found in BD-exposed cells indicating enhanced lipid peroxidation. Malondialdehyde generation was significantly suppressed by 2-MAC and DFO. These results demonstrate that the organophosphate BD can cause direct tubular cytotoxicity, and implicate, at least in part, a role for ROS and accompanying lipid peroxidation in cytotoxicity. Based on these direct in vitro findings, it is hypothesized that, besides hypotension that often accompanies OP intoxication, OP-induced oxidative stress at the tubular level may play a role in the pathogenesis of acute tubular necrosis. (+info)
Cytotoxicity of antiviral nucleotides adefovir and cidofovir is induced by the expression of human renal organic anion transporter 1.
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The transport of organic anions in proximal convoluted tubules plays an essential role in the active secretion of a variety of small molecules by the kidney. In addition to other anionic substrates, the human renal organic anion transporter 1 (hOATI) is capable of transporting the nucleotide analogs adefovir and cidofovir. To investigate the involvement of hOATI in the mechanism of nephrotoxicity associated with these two clinically important antiviral agents, Chinese hamster ovary (CHO) cells were stably transfected with hOATI cDNA. The resulting CHOhOAT cells showed probenecid-sensitive and pH-dependent uptake of p-aminohippurate (Km = 15.4 FtM, V,,, ..ax = 20.6 pmol/106 cells min), a prototypical organic anion substrate. In addition, the stably expressed hOATI mediated efficient transport of adefovir (Km, = 23.8 tLM, V, a,, = 46.0 pmol/106 cells min) and cidofovir (K, = 58.0 /iM, Vt,ax = 103 pmol/106 cells * min) such that the levels of intracellular metabolites of both nucleotides were > 1 00-fold higher in CHOh OAT cells than in parental CHO. Consequently, adefovir and cidofovir were approximately 500-fold and 400-fold more cytotoxic, respectively, in CHOh OAT cells compared to CHO. The cytotoxicity of both drugs in CHOh OAT cells was markedly reduced in the presence of hOATI inhibitors. The cyclic prodrug of cidofovir, which exhibits reduced in vivo nephrotoxicity, was a poor substrate for hOATI and showed only marginally increased cytotoxicity in CHOh OAT cells. In conclusion, these studies demonstrate that hOATI plays a critical role in the organ-specific toxicity of adefovir and cidofovir, and indicates that CHOh OAT cells may represent a useful in vitro model to investigate the potential nephrotoxicity of clinically relevant organic anion agents. (+info)
Nosocomial poisoning associated with emergency department treatment of organophosphate toxicity--Georgia, 2000.
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Emergency department (ED) staff caring for patients contaminated with toxic chemicals are at risk for developing toxicity from secondary contamination. This report describes three cases of occupational illnesses associated with organophosphate toxicity caused by exposure to a contaminated patient and underscores the importance of using personal protection equipment (PPE) and establishing and following decontamination procedures in EDs and other areas of acute care hospitals. (+info)
Determination of glufosinate ammonium and its metabolite, 3-methylphosphinicopropionic acid, in human serum by gas chromatography-mass spectrometry following mixed-mode solid-phase extraction and t-BDMS derivatization.
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A method for the analysis of glufosinate ammonium (GLUF) and its metabolite 3-methylphosphinicopropionic acid (MPPA) in human serum by gas chromatography-mass spectrometry (GC-MS) was developed. Employing a mixed-mode cartridge with both anion exchange action and weak nonpolar interaction, we extracted GLUF and MPPA from the serum and carried out GC-MS analysis of their tert-butyldimethylsilyl derivatives. The detection limits of GLUF and MPPA were 10 pg and 1 pg, respectively. Full mass spectra of 100 pg GLUF and of 10 pg MPPA were easily obtainable. The recovery rate of 90.0+/-11.9% (or better) when the serum concentrations of GLUF and MPPA were 10-0.1 microg/mL. Results of 23 serum samples, from patients with GLUF poisoning, measured by this method correlate well with those derived from the conventional high-performance liquid chromatography method (r = 0.996). The developed GC-MS method is likely to become a useful analytical technique in clinical settings. (+info)
Adverse reaction to atropine and the treatment of organophosphate intoxication.
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Atropine is the drug of choice for treatment of organophosphate nerve agent and insecticide intoxication and has been used for this indication for several decades. Adverse reactions to atropine may occur, and are of two types: toxic and allergic. Toxic reaction, the most common form, results from the anti-muscarinic effects of the drug. Since it is most probably related to interpersonal variation in sensitivity to atropine, toxic effects may appear at the usual therapeutic doses. The second type, allergic reaction, includes local manifestations, usually after the administration of eyedrops, and systemic reaction in the form of anaphylaxis. Since most patients manifest only a mild reaction, allergy testing is not performed and the prevalence of allergy to atropine is therefore not known. Severe allergic reaction to atropine is rare, as evidenced by the small number of case reports in the literature despite the drug's extensive use. Alternative anti-muscarinic drugs recommended for OP poisoning include glycopyrrolate and scopolamine. Glycopyrrolate is a peripheral anti-muscarinic drug that has been studied in comparison to atropine for many clinical indications, while scopolamine is an anti-muscarinic drug with both peripheral and central effects. An acceptable alternative regimen for patients with proven allergy to atropine is a combination of glycopyrrolate with centrally active drugs such as benzodiazepines or scopolamine. (+info)
The toxicity of some organophosphorus compounds to adult Anopheles stephensi.
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The authors have evaluated a number of organophosphorus compounds for residual contact toxicity to adult Anopheles stephensi. Fenthion and malathion were the most promising of the compounds, and wettable powder deposits at a dosage of 1 g/m(2) on plywood remained effective for five months. There was, however, a rapid loss of effectiveness on dried mud bricks stored at 25 degrees C and 50%-55% relative humidity.Diazinon and ronnel were less persistent on plywood. Guthion and coumaphos, although highly toxic by topical application, were both ineffective as contact insecticides when applied as solids in suspension. Trithion and methyl trithion were relatively low in toxicity both by topical application and as contact insecticides. (+info)
Field and laboratory studies on the use of malathion for control of body-lice in Egypt.
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In view of the development of resistance to DDT by Egyptian strains of body-lice, there is a need for another effective and safe insecticide with which they may be controlled. Trials were made in three governorates of the United Arab Republic to compare the effectiveness against these insects of 1% malathion and 10% DDT dusts, 30 g of powder being applied inside the clothing while it was being worn.When susceptibility tests were carried out with the WHO standard technique, the LC(50) was found to be less than 0.04% malathion. In the field, 1% malathion could effectively control lice for three weeks after one application.The 10% DDT dust was less effective, the lice in all three areas showing varying degrees of resistance. However, this insecticide is still considered to be reasonably effective for louse control in central Egypt; in Fayoum Governorate, it might be used but two applications would be needed; north of the Delta its effectiveness appears very doubtful. (+info)
THE SITE OF THE 5-HYDROXYTRYPTAMINE RECEPTOR ON THE INTRAMURAL NERVOUS PLEXUS OF THE GUINEA-PIG ISOLATED ILEUM.
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Dose/response measurements were made on the guinea-pig isolated ileum with six agonists, acetylcholine, 5-hydroxytryptamine, nicotine, dimethylphenylpiperazinium, choline phenyl ether and histamine. The dose effects were repeated in the presence of each of twelve antagonists and one anticholinesterase. Acetylcholine and histamine were chosen because of their direct mode of action on smooth muscle, nicotine, dimethylphenylpiperazinium and choline phenyl ether were used as examples of drugs that act at the ganglionic acetylcholine receptor. 5-Hydroxytryptamine was the drug investigated. Hyoscine blocked the contractions caused by acetylcholine, 5-hydroxytryptamine and the ganglion-stimulants but left the responses to histamine unchanged. The anticholinesterase N,N'-diisopropylphosphorodiamidic fluoride (mipafox) potentiated all the agonists except histamine. The strength of potentiation decreased in the order 5-hydroxytryptamine, nicotine, dimethylphenylpiperazinium and choline phenyl ether, and acetylcholine. The local anaesthetic procaine inhibited to the same extent contractions elicited by 5-hydroxytryptamine, nicotine, dimethylphenylpiperazinium and choline phenyl ether. These results showed that 5-hydroxytryptamine, like nicotine, choline phenyl ether and dimethylphenylpiperazinium, mediated its response through the nervous plexus. Of those tested 5-hydroxytryptamine was the only specific antagonist to 5-hydroxytryptamine; lysergic acid derivatives produced spasm and prolonged changes in tone; phenoxybenzamine caused non-specific block. The diverse modes of action of a number of ganglion-blocking agents were selectively used. Thus hexamethonium, pentolinium, and nicotine in its competitive phase, blocked contractions due to nicotine, dimethylphenylpiperazinium and choline phenyl ether and left those due to 5-hydroxytryptamine, acetylcholine and histamine unchanged. The depolarizing ganglion-blocking agents, dimethylphenylpiperazinium and nicotine, inhibited the responses to all the indirectly acting drugs. Furthermore, mecamylamine, a drug with a less well-defined mode of action, partially inhibited contractions due to 5-hydroxytryptamine in a concentration that blocked those due to nicotine, dimethylphenylpiperazinium and choline phenyl ether. Pempidine, known to act like mecamylamine, did not antagonize 5-hydroxytryptamine. It is concluded that 5-hydroxytryptamine activates specific receptors sited at the intramural parasympathetic ganglion cells. (+info)