Morphological study of the effect of the cytoskeletal disrupting agent carbendazim on the oviduct of the Japanese quail (Coturnix coturnix japonica)

Abstract

Carbendazim (methyl-2-benzimidazole carbamate), a derivative of N-substituted esters of carbamic acid, is widely used as a fungicide on field crops. Carbendazim is of major concern to human and animal health due to the presence of its metabolites and residues in the environment. Several studies have shown the effect of carbendazim on the reproductive systems of male mammals and birds. Relatively little is known of the effect of carbendazim on the female reproductive tract. Therefore, this study was undertaken to establish the effect of carbendazim on the morphological, histochemical and immunohistochemical features of selected regions of the oviduct in the Japanese quail. The functional implication for each region was also considered. A total of 102 sexually mature Japanese quails were used in this study. The study was divided into two experiments. In Experiment I, different doses of carbendazim, in a sunflower oil base, were administered orally to determine the minimum toxic dose which would cause degenerative lesions in the oviduct. The determined dose was used in the Experiment II to establish the time-course effects of carbendazim on the Japanese quail. In Experiment I, 400 mg/kg bodyweight of carbendazim was the minimum toxic dose which caused both macroscopic and microscopic changes in the oviduct. The effect of carbendazim was dose dependent. In Experiment II, the effect of carbendazim was more pronounced with time lapse post-exposure. Macroscopically, increases in oviductal weight, luminal epithelial height and glandular diameter were observed in the initial stages post-exposure. Atrophy and a reduction in oviductal weight were observed in later stages. Microscopically, carbendazim caused hyperaemia and oedema in all sections of the oviduct examined. Leukocytic infiltrations, pyknotic nuclei and cellular swelling were also observed. The histochemical results showed a reduction in PAS positive granules in the luminal and glandular epithelia of all oviductal sections. There were also decreases in the immunostaining intensities of E-cadherin, laminin and vimentin in all oviductal regions. Scanning electron microscopic results showed a loss of cilia, as well as swollen microvilli. Short ciliary stems and shallow pits were also observed in areas exhibiting a loss of cilia. At the ultrastructural level, luminal and glandular epithelia contained cells with degenerating nuclei and cytoplasmic organelles. The observed degenerative changes included pyknosis, karyorhexis, swollen mitochondria, dilated cisternae of rough endoplasmic reticulum, vacuolation and an increased number of lysosomes. Lipofucsin granules and filamentous aggregation were also observed. Compound cilia and myelin figures were frequently observed in the later stages of degeneration. Invagination and occasional duplication of the basal lamina, underlying both luminal and glandular epithelia, were also observed. The observed degenerative changes suggested oviductal regression in carbendazimtreated birds. Degeneration of epithelial and glandular cells may lower the fertility and productivity of exposed birds.