A more striking effect on embryonic development was observed by supplementation of 5 M retinol to groups of oocytes with reduced developmental compe tence in which development of control oocytes to blasto cyst was less than 20%. These results indicate that retinol selleck chem Gemcitabine supplementation during maturation may not benefit oocytes competent to progress, but rather, it improves the viability of oocytes that are developmentally challenged. In support of this, we have shown previously that retinol supplementation during maturation improves develop mental competence of bovine oocytes compromised by heat stress. Since most transcription in the oocyte occurs prior to mat uration during preovulatory development, in vitro culture deprives oocytes of much of this activity.

Meiotic inhibi tors have been used as a potential means of investigating regulation of oocyte transcription and mRNA processing in vitro. Treatment of cumulus enclosed oocytes with 9 cis RA during meiotic arrest was observed to improve cortical granule migration, increase subsequent blastocyst development and increase total cell number. Gomez and co workers suggested that retinoid administra tion may improve mRNA quality based on the observa tion that 9 cis RA increased poly mRNA content in meiotically arrested oocytes. Poly mRNA content of oocytes treated with 9 cis RA or ethanol vehicle was greater in matured oocytes than in oocytes prematured in the presence of 9 cis RA and then matured. Retinol supplementation of embryo culture medium dra matically improved development to the blastocyst stage when cultured in an atmosphere of appro i mately 20% O2 but not in an atmos phere of low O2.

The present study, and all previous in vitro studies demon strating a positive effect of retinoid administered during maturation, were performed in an atmosphere of appro imately 20% O2, a practice common to most laboratories. Together, these data indicate that retinoids may protect embryos from o idative damage, which has been identified as a leading cause of embryonic wastage, especially in vitro. Mammalian cells, including the oocyte and those of the early embryo, have evolved several mechanisms to protect against ROS damage and maintain appropriate balances in REDO reactions. Antio idants present in the oocyte, embryo and or its environment include vitamins A, C and E, pyruvate, glutathione, hypotaurine, taurine, Drug_discovery and cysteamine. Antio idant enzymes pro duced by oocytes and embryos include, copper, zinc supero ide dismutase, manganese SOD, glutathione pero idase, glutamyl cysteine synthase, glutathione reductase, cat alase and others.