Ultrastructural evaluation of mouse oocytes after exposure to the fungicide Mancozeb

Mancozeb is a fungicide, a member of the Dithiocarbamates group, used in the management of fungal diseases of plants, and classifi ed as an endocrine disruptor [1]. Although its low mammalian toxicity, high or repeated exposure to Mancozeb may interfere with reproductive biology. Recent studies on the eff ect of Mancozeb on female fertility evidenced morphological changes associated with an altered p53 expression, in mice granulosa cells and hampered embryo development [2,3]. Data from in vitro experiments have revealed alterations in the meiotic spindle structure of mice oocytes and granulosa cells morphology [4,5]. However, there are no ultrastructural studies performed by Light Microscopy (LM) and Transmission Electron Microscopy (TEM), on mammalian oocytes exposed to Mancozeb. This preliminary study aims to evaluate the ultrastructure of M-II mouse mature oocytes obtained by puncturing antral follicles of PMSG-treated prepubertal CD1 female mice and cultured in vitro in DMEM+5ûS+pen/step without (control) or with increasing concentrations of Mancozeb (from 0.001 to 1 μg/ml). After collection, oocytes were fi xed in 2.5% glutaraldehyde/PBS and subjected to the standard preparative for LM and TEM [5]. At low concentrations, ultrastructural data showed intact zona pellucida, thin perivitelline space, few and irregular microvilli distributed on the oolemma, normal mitochondria dispersed in the cytoplasm, and a few cortical granules visible. At higher concentrations, the zona pellucida appeared intact with an indistinguishable perivitelline space, an irregular or reduced distribution of microvilli, and a decreased presence/distribution of the organelles. In particular, diff erently from the previous group, the ooplasm showed the presence of hooded mitochondria, characterized by a reduced functional surface, with no visible cortical granules. In conclusion, Mancozeb induced dose-dependent toxicity on the mouse oocyte ultrastructure, with alterations in the oolemma, a reduction of the microvilli, and a decreased density of intracellular organelles. These morphological changes could adversely aff ect developmental competence and reproductive potential, as observed in cases of infertility associated with pesticide exposure.