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GLUTATHIONE (GSH) CONCENTRATIONS VARY WITH THE CELL CYCLE IN MATURING HAMSTER OOCYTES, ZYGOTES AND PRE-IMPLANATION EMBRYOS
Citation:
Zuelke, K. A., S C. Jeffay, R M. Zucker, AND S D. PERREAULT. GLUTATHIONE (GSH) CONCENTRATIONS VARY WITH THE CELL CYCLE IN MATURING HAMSTER OOCYTES, ZYGOTES AND PRE-IMPLANATION EMBRYOS. MOLECULAR REPRODUCTION AND DEVELOPMENT. Alan R Liss, Inc, New York, NY, 64(1):106-112, (2003).
Description:
Abstract
Glutathione (GSH) is thought to play critical roles in oocyte function including spindle maintenance and provision of reducing power needed to initiate sperm chromatin decondensation. Previous observations that GSH concentrations are higher in mature than immature oocytes and decline after fertilization, suggest that GSH synthesis may be associated with cell cycle events. To explore this possibility, we measured the concentrations of glutathione (GSH) in Golden hamster oocytes and zygotes at specific stages of oocyte maturation and at intervals during the first complete embryonic cell cycle. Between 2 and 4 hours after the hormonal induction of oocyte maturation, GSH concentrations increased significantly (~ doubling) in both oocytes and their associated cumulus cells. This increase was concurrent with germinal vesicle breakdown and the condensation of metaphase I chromosomes in the oocyte. GSH remained high in ovulated, metaphase II oocytes, but then declined significantly, by about 50%, shortly after fertilization, as the zygote progressed back into interphase (the pronucleus stage). GSH concentrations then plummeted by the two-cell embryo stage and remained at only 10% of those in metaphase II oocytes throughout pre-implantation development. These results demonstrate that oocyte GSH concentrations fluctuate with the cell cycle, being highest during meiotic metaphase, the critical period for spindle growth and development and for sperm chromatin remodeling. These observations raise the possibility that GSH synthesis in maturing oocytes is regulated by gonadotropins, and suggest that GSH is more important during fertilization than during pre-implantation embryo development.