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.
