Toxic effects of the mycotoxin zearalenone and its derivatives on in vitromaturation of bovine oocytes and 17 beta-estradiol levels in mural granulosa cell cultures

Moulds parasites of livestock foodstuffs alter the quality of grains by syn thetising mycotoxins. Zearalenone (ZEA) and its derivatives (alpha- and bet a -zearalenol, zeranol, taleranol and zearalanone) are produced by fungi of the genus Fusarium and, after ingestion via contaminated cereals, may lead to fertility disturbances and other reproductive pathologies. Zearalenone, alpha -zearalenol and zearalanone were tested, at levels ranging from 0.3 to 30 mug/ml, in order to evaluate the effect on the in vitro maturation (I VM) rate of bovine oocytes and on the formation of 17 beta -estradiol in su pernatants of mural granulosa cells (GC) cultures. These compounds induced dose-dependent oocyte maturation delay and chromatin abnormalities. Maturat ion of oocytes to metaphase II (M II) was inhibited in oocytes cultured in the presence of 30 mug/ml ZEA, alpha -zearalenol or zearalanone, with a sig nificant increase in chromatin abnormalities occurring in the presence of Z EA (P<0.05) and <alpha>-zearalenol (P<0.001). In preliminary trials on 17<b eta>-estradiol formation, at the same testing concentration, higher levels of 17 beta -estradiol were found in the presence of alpha -zearalenol (mean value 1.6 ng/ml) with respect to ZEA and zearalanone (mean estradiol conce ntrations of 0.06 and 0.5 ng/ml, respectively). These data demonstrate a ne gative effect of ZEA and its derivatives on meiotic progression of bovine o ocytes, possibly attributable to a toxic mechanism not related to the bindi ng affinity of these compounds to estrogen receptor sites, and support prev ious observations that alpha -zearalenol acts as a stronger estrogenic indu cer than the original molecule (ZEA). (C) 2001 Elsevier Science Ltd. All ri ghts reserved.