Ototoxicity of an association of insecticides compounds containing dichlorvos and cypermethrin in Wistar rats

ABSTRACT Purpose: to evaluate possible ototoxicity secondary to exposure to a combination of pesticides (dichlorvos and cypermethrin based insecticides). Methods: the Wistar rats were divided into 3 groups (12 animals per group): control (water), positive control for hearing damage (cisplatin) and experimental (exposed to dichlorvos and cypermethrin). The amplitude of distortion product otoacoustic emissions was assessed before and after the exposure. Systemic toxicity signs were also evaluated (clinical signs, weight gain and plasma cholinesterase). Wilcoxon test analyzed the post-exposure amplitudes compared to pre-exposure and Kruskal Wallis following Dunn’s post hoc tests analyzed the amplitudes’ variation. Normally distributed variables were evaluated by Student's t test. Results: body weight and plasma cholinesterase values were similar comparing the pre and post exposure in the experimental group. The control group did not manifest significant amplitude reduction of otoacoustic emissions between the pre and post evaluation. In the group exposed to cisplatin there was a significant reduction in amplitudes at 12 kHz on the right (p = 0.006; Wilcoxon) and 4 kHz on the left (p = 0.032; Wilcoxon). In the group exposed to pesticides, there was a significant reduction in the right ear at 4 kHz (p = 0.034; Wilcoxon) and 8 kHz (p = 0.019; Wilcoxon) and in the left ear at 4 kHz (p = 0.007; Wilcoxon), 6 kHz (p = 0.023; Wilcoxon), 8 kHz (p = 0.045; Wilcoxon) and 12 kHz (p = 0.028; Wilcoxon). Conclusion: there was ototoxicity in the experimental group, without a relevant systemic toxicity.

摘要
研究目的：评估暴露于敌敌畏（dichlorvos）与氯氰菊酯（cypermethrin）类复配农药后可能产生的耳毒性。
方法：将Wistar大鼠（Wistar rats）分为3组，每组12只：对照组（给予纯水）、听力损伤阳性对照组（给予顺铂（cisplatin））、实验组（暴露于敌敌畏与氯氰菊酯）。分别于暴露前后检测畸变产物耳声发射（distortion product otoacoustic emissions）的幅值，并评估全身毒性体征（包括临床症状、体重增长情况及血浆胆碱酯酶水平）。采用Wilcoxon检验（Wilcoxon test）比较暴露前后的幅值差异，采用Kruskal Wallis检验（Kruskal Wallis test）结合Dunn事后检验分析各组间的幅值变化；对于符合正态分布的变量，则采用Student t检验（Student's t test）进行分析。
结果：实验组暴露前后的体重及血浆胆碱酯酶水平无显著差异。对照组在暴露前后的耳声发射幅值未出现明显降低。顺铂暴露组大鼠右耳12 kHz处（p=0.006；Wilcoxon检验）及左耳4 kHz处（p=0.032；Wilcoxon检验）的幅值显著降低。农药暴露组大鼠右耳4 kHz（p=0.034；Wilcoxon检验）、8 kHz（p=0.019；Wilcoxon检验）处，以及左耳4 kHz（p=0.007；Wilcoxon检验）、6 kHz（p=0.023；Wilcoxon检验）、8 kHz（p=0.045；Wilcoxon检验）、12 kHz（p=0.028；Wilcoxon检验）处的幅值均出现显著降低。
结论：实验组大鼠出现耳毒性，但未观察到明显的全身毒性反应。