Alterações na superfície ocular de coelhos tratados com formulações do herbicida ácido diclorofenoxiacético (2,4 d), utilizando a graduação do teste ocular de draize

AUTOR(ES)

Lilian Verdolin Milo Collor

DATA DE PUBLICAÇÃO

2007

RESUMO

Ocular irritation test is required by the Brazilian government authorities during the registration process of pesticide products, and it is essential for its toxicological classification. The present study evaluated the clinical and microscopic changes in the eye surface of rabbits after treatment with four pesticide formulations containing the herbicide 2,4-D dichlorophenoxyacetic acid (2,4-D), using the Draize scale for grading the ocular irritation. Eighty four animals were used in the experiment, being 21 for each formulation, distributed in 7 groups. A single dose of 0.1 mL or g was directly applied to the conjunctive sac of the left eye of each animal, and the right eye being used as control. Changes in the cornea, iris and conjunctives were graduated after 1, 24, 48 and 72 hours and 7, 14 and 21 days after treatment. In each interval, three animals were killed, the eyes removed and the ocular tissues prepared for the histological examination. Clinical results showed no proportionality between concentration of 2,4-D in the formulation and severity of corneal damage. The products 1 and 2, with lower 2,4-D concentration and pH near the neutrality, caused discrete and moderate changes in the cornea when compared with the products 3 and 4, which caused moderate and accentuated changes. Lesions produced in the corneal epithelium were repaired during the experiment, with exception of those in one animal treated with product 3 and three animals treated with product 4 which had corneal perforation. Infiltrates of polymorphonuclear neutrophil cells were observed microscopically in the majority of the inflammatory events clinically noted on the cornea, iris and conjunctives. However, not always the intensity of the changes observed macro and microscopically were correlated. Microscopy showed corneal hyperplasia, queratinization and desquamation and inflammation of the ciliary body of many animals as a result of the treatment, changes that can affect the vision but are not normally observed during the clinical examination. The current Brazilian legislation is conservative, as it considers any product that shows corneal opacity, reversible or not after 7 days, as extremely toxic. The present work indicates the need to update this legislation according to the international procedures.

ASSUNTO(S)

ocular irritation pesticide teste de draize agrotóxico 2,4-d irritação ocular draize test 2,4-d ciencias da saude

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