title: Acute exposure to the insecticide O,S-dimethyl phosphoramidothioate (methamidophos) leads to impairment of cardiovascular reflexes in rats.
abstract: Poisoning by organophosphorus insecticides is often accompanied by cardiac complications which may be serious and even fatal. However, the effects of these compounds on the cardiovascular mechanisms involved in blood pressure regulation are not known. The aim of this study was to evaluate the effects of a sublethal dose (8 mg/kg, i.p.) of the organophosphorus methamidophos on chemoreceptor (CR) and Bezold-Jarisch (BJR) cardiovascular reflexes. Male Wistar rats were treated with single intraperitoneal injections of methamidophos in saline (n=23) or saline (0.9 percent, n=20) and underwent catheterization of femoral artery and vein one day after the injections. Cardiovascular recordings were performed 24h after the catheterization procedure. Plasma cholinesterase (ChE) activity was measured 24h after similar treatments in separate groups (n=10/group). The bradycardic component of CR and BJR was significantly attenuated in animals treated with methamidophos. The ChE activity was 80 percent reduced in the methamidophos-treated animals. Methamidophos impairment of the bradycardic component of two important cardiovascular reflexes may contribute to the cardiovascular toxicity associated with acute organophosphorus insecticides exposure.
authors.affiliation: Department of Physiological Sciences, Federal University of Espírito Santo, Vitória, ES, Brazil.
authors.forename: Gabriella Xavier
authors.initials: GX
authors.lastname: Maretto
authors.forename: Cristina Paula
authors.initials: CP
authors.lastname: do Nascimento
authors.forename: Luciana Mesquita
authors.initials: LM
authors.lastname: Passamani
authors.forename: Luiz Carlos
authors.initials: LC
authors.lastname: Schenberg
authors.forename: Tadeu Uggere
authors.initials: TU
authors.lastname: de Andrade
authors.forename: Suely Gomes
authors.initials: SG
authors.lastname: Figueiredo
authors.forename: Hélder
authors.initials: H
authors.lastname: Mauad
authors.forename: Karla Nívea
authors.initials: KN
authors.lastname: Sampaio
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002319:Cardiovascular System / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D007306:Insecticides / Q000633:toxicity*; D007928:Lethal Dose 50; D008297:Male; D009946:Organothiophosphorus Compounds / Q000633:toxicity*; D051381:Rats; D017208:Rats, Wistar; D012018:Reflex
chemical_list: D007306:Insecticides; D009946:Organothiophosphorus Compounds; C014655:methamidophos