Effects of Ochratoxin A on development potential of lamb oocytes

The aim of the study was to evaluate the effects of OTA,a mycotoxin produced by Aspergillus and Penicillium fungi and reported as an ubiquitous contaminant of food and feed1,2on: 1) nuclear and cytoplasmic maturationand 2) developmental potential of lamb oocytes.Cumulus-oocyte complexes (COCs) were recovered at local slaughterhouses from lamb ovaries. During in vitro maturation (IVM)3, COCs were exposed to 10μM OTA, asin a previous study in mice[4]. Vehiclecontrols (IVM medium with 1% methanol) and standard controls (IVM medium without vehicle) were used. In Experiment 1 (Exp.1), after IVM, COCs underwent cumulus removal and staining of nuclear chromatin and mitochondria (mt)3. Oocytes in metaphase II underwent confocal microscopy to analyze their mt distribution pattern3. In Exp.2, oocytes undewent IVM, in vitro fertilization (IVF) and embryo culture up to day 73. Cleavage and blastocyst formation rates were recorded. Data were analysed by Chi-square test (differences significant when P<0.05). In Exp.1, 218 oocytes were analyzed. Lack of vehicle-related effects was noticed (23/37, 62% vs 62/96, 65%, for oocytes cultured with or without vehicle; NS). OTA tended to reduce the maturation rate (39/85, 46% vs 23/37, 62%, for exposed and controls, respectively) even without statistical significance. Instead, it reduced the rate of oocytes with healthy perinuclear/pericortical mt pattern (4/39, 10% vs 9/23, 39%, P<0.05). In Exp.2, (n=275 oocytes analyzed)no effects were noticed on cleavage (22/90, 24%; 24/92, 26%; 31/93, 33%) and blastocyst rates (4/90, 4%; 1/92, 1%; 2/93, 2%) between OTA and controls with or without vehicle(P>0.05). In conclusion, OTA hinderednuclear and cytoplasmic maturation of lamb oocytes but do no affect their developmental potential.