EXPRESSION OF GENES ENCODING ANTIOXIDANT ENZYMES IN PREIMPLANTATION MOUSE AND COW EMBRYOS AND PRIMARY BOVINE OVIDUCT CULTURES EMPLOYED FOR EMBRYO COCULTURE

Preimplantation embryos from a variety of mammalian species contrast m arkedly in their response to culture in vitro. Murine preimplantation embryos display a wider tolerance than other mammalian species to cult ure environments, and this has contributed to the development of sever al effective defined culture media. Embryo coculture on somatic cells remains the most effective method of supporting reasonable rates of bo vine preimplantation development in vitro. The patterns of gene expres sion for several antioxidant enzymes during preimplantation murine and bovine development were examined by use of the reverse transcription- polymerase chain reaction technique to determine whether the different ial developmental capacity of mammalian preimplantation embryos in cul ture may reflect variations in the patterns of expression for a series of antioxidant enzymes. Transcripts for catalase, CuZn-containing sup eroxide dismutase (CuZn-SOD), Mn-SOD, glutathione peroxidase (GPX), an d glutamylcysteine synthetase (GCS) were detected in mouse embryos at all stages of development regardless of in vivo or in vitro developmen t. Preimplantation cow embryos produced by in vitro procedures express ed mRNAs for catalase, CuZn-SOD and GPX, whereas transcripts for Mn-SO D were not detected at any stage, GCS transcripts, although present in stages up to the morula, were not detected in cow blastocysts. Analys is of antioxidant gene expression in both bovine primary oviductal cel l monolayer cultures and nonattached, ciliated oviductal cell vesicle cultures revealed a constitutive pattern of expression of all five enz ymes for the 8-day culture interval. These experiments suggest that di fferences in gene expression may contribute to the variation in the ab ility of embryos to develop in vitro with respect to levels of oxygen and dependence on coculture.