Análise da remodelação cardíaca de ratos submetidos à exposição crônica ao herbicida 2,4-D

Abstract

Background: 2,4-Dichlorophenoxyacetic acid (2,4-D) is one of the most widely used chlorophenoxy herbicides worldwide due to its selectivity, efficiency and low cost. 2,4-D is rapidly absorbed in the respiratory tract and can toxically affect both animals and humans in a wide range of organs, such as liver, kidneys, muscles, lungs, gastrointestinal tract, nervous system (central, peripheral), endocrine, reproductive system and heart. Workers who use herbicides have a high risk of contamination by residues, which can occur through contact with the skin, ingestion and inhalation. Objective: To evaluate the chronic effects on cardiac remodeling of adult male Wistar rats that inhaled 2,4-D by nebulization. Methods: 30 adult male Wistar rats were used, divided into 3 groups: a control group exposed to the nebulization of 10 ml of 0.9% sodium chloride solution (GCI, n=10), a low concentration group exposed to 2.4-D with 3.71x10-3g of active ingredient per hectare (GBI, n=10) and a high concentration group exposed to 2.4-D with 9.28x10-3g of active ingredient per hectare (GAI, n=10). During an exposure period of 180 days, two boxes connected to ultrasonic nebulizers were used to spray the herbicides. After this period, the rats were euthanized for the collection and study of cardiac tissue. Cardiac remodelling was assessed in terms of hypertrophy, fibrosis and vascularization. To assess hypertrophy, the areas of the cardiomyocytes were evaluated after staining with hematoxylin and eosin. To assess connective tissue, fibrosis measurements were analyzed using slides stained with Picrosirius Red (PSR). Arteriolar thickness was analyzed using the Verhoeff technique (VVG). For all these approaches, the fractal dimension (FD) was applied using the box-counting method. Data normality was assessed using the Shapiro-Wilk test. Parametric data was evaluated by ANOVA followed by Tukey's test and for non-parametric data the Kruskal-Wallis test was used followed by Dunn's post-test (p<5%). Results: Analysis of the measurement of cardiomyocyte area showed no change; there was an increase in collagen in the animals exposed to a low dose of 2,4-D (p<0.0001) and evaluation of the LV by means of fractal dimension showed a reduction in fractal dimension in GAI when compared to GCI (p=0.010); and there was no difference in the amount between type I and III collagens; and analysis of the thickness of the arterioles showed no change. Conclusion: After 180 days of exposure to the pesticide 2,4-D there was an alteration in cardiac remodeling demonstrated by the increase in collagen and the dimension of fractility.