Mammalian voltage-gated calcium channels are potently blocked by the pyrethroid insecticide allethrin. (1/13)

Pyrethroids are commonly used insecticides for both household and agricultural applications. It is generally reported that voltage-gated sodium channels are the primary target for toxicity of these chemicals to humans. The phylogenetic and structural relatedness between sodium channels and voltage-gated calcium (Ca) channels prompted us to examine the effects of the type 1 pyrethroid allethrin on the three major classes of mammalian calcium channels exogenously expressed in human embryonic kidney 293 cells. We report that all classes of mammalian calcium channels are targets for allethrin at concentrations very similar to those reported for interaction with sodium channels. Allethrin caused blockade with IC(50) values of 7.0 microM for T-type alpha(1G) (Ca(v)3.1), 6.8 microM for L-type alpha(1C) (Ca(v)1.2), and 6.7 microM for P/Q-type alpha(1A) (Ca(v)2.1) channels. Mechanistically, the blockade of calcium channels was found to be significantly different than the prolonged opening of mammalian sodium channels caused by pyrethroids. In all calcium channel subtypes tested, allethrin caused a significant acceleration of the inactivation kinetics and a hyperpolarizing shift in the voltage dependence of inactivation. The high-voltage-activated P/Q- and L-type channels showed a frequency of stimulation-dependent increase in block by allethrin, whereas the low-voltage-activated alpha(1G) subtype did not. Allethrin did not significantly modify the deactivation kinetics or current-voltage relationships of any of the calcium channel types. Our study indicates that calcium channels are another primary target for allethrin and suggests that blockade of different types of calcium channels may underlie some of the chronic effects of low-level pyrethroid poisoning.  (+info)

Metofluthrin: a potent new synthetic pyrethroid with high vapor activity against mosquitoes. (2/13)

(1R)-trans-Norchrysanthemic acid fluorobenzyl esters are synthesized and their structure-activity relationships are discussed. These esters show outstanding insecticidal activity against mosquitoes. In particular, the 2,3,5,6-tetrafluoro-4-methoxymethylbenzyl analog (metofluthrin) exhibits the highest potency, being approximately forty times as potent as d-allethrin in a mosquito coil formulation when tested against southern house mosquitoes (Culex quinquefasciatus). Metofluthrin also exhibits a significant vapor action at room temperature.  (+info)

Efficacy of thermal fog application of deltacide, a synergized mixture of pyrethroids, against Aedes aegypti, the vector of dengue. (3/13)

We evaluated the efficacy of indoor and peridomestic thermal fog applications of deltacide, a synergized mixture of pyrethroids (S-bioallethrin 0.7% w/v, deltamethrin 0.5% w/v and piperonyl butoxide 8.9% w/v) against adult populations of Aedes aegypti in Chennai, Tamil Nadu, India. We bioassayed adult caged mosquitoes, counted indoor resting and human landing adult mosquitoes and assessed the percentage of potential breeding sites with Aedes larvae. The bioassay mortalities indicated that the knockdown and killing effect was greater when fogging was applied inside houses rather than around them. Peridomestic thermal fogging reduced the resting and biting populations by 76% and 40%, respectively for the 3 days after treatment, whereas indoor fogging suppressed adult populations for 5 days.  (+info)

Ninety-day toxicity and one-generation reproduction study in rats exposed to allethrin-based liquid mosquito repellent. (4/13)

Rats exposed to liquid mosquito repellent (LMR) containing allethrin (3.6% w/w) 8-hrs/ day for a period of ninety days did not produce any signs of toxicity or death. Significant increases in relative weight of liver and adrenal in males, brain and thyroid in females were observed. No significant changes were noticed in clinical enzyme profile, gonadal enzymes and histopathology of vital organs except mild changes in the activities of liver and serum alkaline phosphates (ALP), testicular glucose-6-phosphate dehydrogenase (G-6PDH) and epididymal sorbitol dehydrogenase (SDH). Rats exposed to LMR for one generation had not produced changes in their reproductive indices such as fertility index, gestation index, live pups/ dam and sex ratio. There was no change in the preweanling evaluation of pups such as survival and growth index on post-natal days (PND) 0, 4, 7,14 and 21. No significant pathomorphological changes were observed in liver, brain, kidney and gonads of PND 21 pups. Absences of any major adverse effects in the adult as well as weanling rats suggest the safe use of allethrin-based LMR.  (+info)

Nationwide investigation of the pyrethroid susceptibility of mosquito larvae collected from used tires in Vietnam. (5/13)

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Lack of insecticidal effect of mosquito coils containing either metofluthrin or esbiothrin on Anopheles gambiae sensu lato mosquitoes. (6/13)

Use of mosquito coils for personal protection against malaria and mosquito nuisance is advocated under mosquito and malaria control programmes. We performed field studies of mosquito coils containing either metofluthrin or esbiothrin in experimental huts situated in Kamhororo village, Gokwe district, Zimbabwe. All tests were performed on 3-5 day old reared female Anopheles gambiae sensu lato mosquitoes. The burning times were 9hr 20min for mosquito coils containing metofluthrin and 8 hr for those containing esbiothrin and the results were significantly different (p = <0.001). The mean knock down rate for mosquito coils containing metofluthrin was 90% and that for esbiothrin was 73.3% and the results were significantly different (p = 0.00). Mosquito coils containing metofluthrin had a mean repellence of 92.7% as compared to 85.4% for esbiothrin and the results were not significantly different (p=0.27). The protection time as required by EPA (1999) was 6 hr for mosquito coils containing metofluthrin and 5 hr for those containing esbiothrin. The mean insecticidal effect of mosquito coils containing metofluthrin was 84% as compared to 83% for those containing esbiothrin and the results were not significantly different (p = 0.56). Both mosquito formulations could not be classified as having insecticidal effect since none of them met the 95% mortality rate criteria.  (+info)

Allethrin differentially modulates voltage-gated calcium channel subtypes in rat PC12 cells. (7/13)

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Divergent actions of the pyrethroid insecticides S-bioallethrin, tefluthrin, and deltamethrin on rat Na(v)1.6 sodium channels. (8/13)

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