Departamento de Biologia, Instituto de Biociências, Universidade Estadual Paulista Júlio de Mesquita Filho, UNESP, Rio Claro, SP, Brazil.
Exp Parasitol. 2012 Jun;131(2):153-6. doi: 10.1016/j.exppara.2012.03.010. Epub 2012 Mar 29.
As recent studies have shown that ecdysteroids may play a major role in the regulation of vitellogenesis in Ixodidae, the present study quantified, by means of a radioimmunoassay, the levels of ecdysteroids present in the hemolymph of semi-engorged females of Rhipicephalus sanguineus ticks obtained from control females (exposed to distilled water) and those exposed to increasing concentrations of permethrin. The levels of ecdysteroids decreased significantly as the concentration of permethrin increased, suggesting that this compound could be an inhibitor of ecdysteroids secretion, and consequently interfering with the reproductive ability of these ticks, since this hormone is responsible for the synthesis and incorporation of vitellogenin by oocytes. This study complements the previous results with R. sanguineus semi-engorged females, showing that permethrin is a potent agent causing major morphological changes in tick oocytes, such as the appearance of large vacuoles in the cytoplasm, reduction in the amount of yolk granules and a decrease in oocyte size, thus culminating in cell death and consequently reducing or preventing reproduction in treated females. The findings that permethrin leads to a decrease in ecdysteroid titers could represent an entry step into this scenario.
由于最近的研究表明蜕皮激素可能在硬蜱属的卵黄发生调节中起主要作用，本研究通过放射免疫测定对半饱血雌性 Rhipicephalus sanguineus 蜱的血淋巴中存在的蜕皮激素水平进行了定量，这些蜱是从对照雌性（暴露于蒸馏水中）和暴露于递增浓度的氯菊酯的雌性中获得的。随着氯菊酯浓度的增加，蜕皮激素的水平显著下降，这表明这种化合物可能是蜕皮激素分泌的抑制剂，从而干扰这些蜱的生殖能力，因为这种激素负责卵母细胞的卵黄蛋白原的合成和掺入。本研究补充了之前对半饱血雌性 R. sanguineus 的研究结果，表明氯菊酯是一种有效的药剂，可导致蜱卵母细胞发生重大形态变化，如细胞质中出现大空泡、卵黄颗粒数量减少以及卵母细胞大小减小，最终导致细胞死亡，从而减少或防止处理后的雌性繁殖。氯菊酯导致蜕皮激素滴度下降的发现可能代表了进入这种情况的一个步骤。
