GLUTATHIONE SYNTHESIS DURING IN-VITRO MATURATION OF BOVINE OOCYTES - ROLE OF CUMULUS CELLS

Glutathione (GSH) synthesis during in vitro maturation (IVM) has been shown to play an important role in embryo development. The present stu dy was carried out to evaluate the role of cumulus cells in GSH synthe sis during IVM of bovine oocytes in the presence of cystine, cysteine, the cysteine analogue N-acetylcysteine, and cysteamine. For this purp ose, cumulus-oocyte complexes (COCs), denuded oocytes (DOs), and DOs i n coculture with a cumulus cell monolayer were used. An increase in GS H level stimulated by cystine was observed only in the presence of cum ulus cells, either with COCs or in DOs matured on a coculture monolaye r. Addition of cysteine and cysteamine to IVM medium increased GSH lev els in COCs and DOs. N-Acetylcysteine increased GSH levels only in DOs . Moreover, cumulus cells contributed to the stimulatory effect exerte d by cysteine and cysteamine on GSH synthesis in COCs. These results i ndicate that cumulus cells during IVM play an important role in oocyte GSH synthesis, allowing the oocytes to use cystine and contributing t o the stimulatory effect exerted by cysteine and cysteamine. In additi on, these results demonstrate that IVM medium supplemented with cystei ne or cysteamine increased GSH content in oocytes without cumulus mass (DO) and in the absence of a cumulus cell monolayer. This may be usef ul to increase the efficacy of IVM of those oocytes having few cumulus cell layers, in a system without coculture.