Akutna oralna toksičnost organofosfornih insekticida i inhibicija kolinesteraza u pilića

Acute toxic effects of three commonly used insecticidal preparations of the organophosphates chlorpyrifos, diazinon, and dichlorvos were examined in mixed breed broiler chicks, and cholinesterase activity in plasma and brain were measured. The acute (24 h) oral median lethal doses (LD50) of chlorpyrifos, diazinon, and dichlorvos were 10.79 mg kg-1, 6.32 mg kg-1, and 6.30 mg kg-1, respectively, as determined by the up-and-down method in chicks. Signs of cholinergic toxicosis in the chicks appeared within two hours after dosing, and they included salivation, lacrimation, gasping, frequent defecation, drooping of wings, tremors, convulsions, and recumbency before death. Halving the oral LD50 of chlorpyrifos (5 mg kg-1), diazinon (3 mg kg-1), and dichlorvos (3 mg kg-1) caused immobility and wing drooping, but not the clinical signs of cholinergic toxicity. However, at full LD50 doses of these insecticides, chicks showed clinical signs of cholinergic toxicity similar to those seen in the LD50 experiments. Two out of six chicks died within two hours after treatment with LD50 doses of chlorpyrifos and dichlorvos, whereas LD50 dosing with diazinon caused death in three out of six chicks. Compared to control values, the insecticides reduced plasma and whole brain cholinesterase activities by 29 % to 84 % and 18 % to 77 %, respectively, depending on the dose. The decrease in plasma cholinesterase correlated well (r = 0.82) with that of the brain. These data suggest that organophosphate insecticides administered orally at LD50 doses induce clinical signs of cholinergic poisoning and concurrently reduce brain and plasma cholinesterase activities in chicks.Ispitano je akutno toksično djelovanje triju često rabljenih organofosfornih insekticida klorpirifosa, diazinona i diklorvosa u brojlera te je izmjerena aktivnost kolinesteraza u njihovoj plazmi i mozgu. Srednja letalna doza LD50 klorpirifosa iznosila je 10,79 mg kg-1, diazinona 6,32 mg kg-1 te diklorvosa 6,30 mg kg-1. Prvi su se znakovi kolinergičkoga sindroma u pilića javili unutar dva sata od oralne primjene, a obuhvaćali su slinjenje, suženje, teško disanje, učestalu defekaciju, obješena krila, drhtavicu, grčenje i nesposobnost stajanja uoči smrti. Oralna primjena polovice srednje letalne doze insekticida klorpirifosa (5 mg kg-1), diazinona (3 mg kg-1) i diklorvosa (3 mg kg-1) dovela je do nepokretnosti i obješenih krila, ali bez kliničkih znakova kolinergičke toksičnosti koji su uočeni kod pokusa radi utvrđivanja srednje letalne doze (LD50). Međutim, doze ovih insekticida koje su odgovarale LD50, dovele su do kliničkih znakova kolinergičke toksičnosti sličnih onima zamijećenim kod utvrđivanja LD50. Dva od šest pilića uginula su unutar dva sata od primjene bilo klorpirifosa bilo diklorvosa u dozama koje su odgovarale LD50, dok je diazinon u odgovarajućoj srednjoj letalnoj dozi uzrokovao smrt triju od šest pilića. U odnosu na kontrolne vrijednosti, insekticidi su doveli do smanjenja aktivnosti kolinesteraze koja je ovisila o dozi, a kretala se od 29 % do 84 % u plazmi te od 18 % do 77 % u mozgu. Pad aktivnosti kolinesteraze u plazmi dobro je korelirao s njezinim padom u mozgu (r=0,82). Ovi podaci upućuju na to da oralna primjena organofosfornih insekticida u dozama koje odgovaraju srednjoj letalnoj dozi dovode do znakova kolinergičkoga trovanja u pilića te do istodobnoga pada aktivnosti kolinesteraza u mozgu i plazmi