Regulation of redox metabolism in the mouse oocyte and embryo

Remi Dumollard, Zoe Ward, John Graham Carroll, Michael R Duchen

Research output: Contribution to journalArticleResearchpeer-review

135 Citations (Scopus)

Abstract

Energy homeostasis of the oocyte is a crucial determinant of fertility. Following ovulation, the oocyte is exposed to the unique environment of the Fallopian tube, and this is reflected in a highly specialised biochemistry. The minute amounts of tissue available have made the physiological analysis of oocyte intermediary metabolism almost impossible. We have therefore used confocal imaging of mitochondrial and cytosolic redox state under a range of conditions to explore the oxidative metabolism of intermediary substrates. It has been known for some time that the early mouse embryo metabolises external pyruvate and lactate but not glucose to produce ATP. We now show at the level of single oocytes, that supplied glucose has no effect on the redox potential of the oocyte. Pyruvate is a cytosolic oxidant but a mitochondrial reductant, while lactate is a strong cytosolic reductant via the activity of lactate dehydrogenase. Unexpectedly, lactate-derived pyruvate appears to be diverted from mitochondrial oxidation. Our approach also reveals that the level of reduced glutathione (GSH) in the oocyte is maintained by glutathione reductase, which oxidises intracellular NADPH to reduce oxidised glutathione. Surprisingly, NADPH does not seem to be supplied by the pentose phosphate pathway in the unfertilised oocyte but rather by cytosolic NADP-dependent isocitrate dehydrogenase. Remarkably, we also found that the oxidant action of pyruvate impairs development, demonstrating the fundamental importance of redox state on early development.
Original languageEnglish
Pages (from-to)455 - 465
Number of pages11
JournalDevelopment
Volume134
Issue number3
DOIs
Publication statusPublished - 2007
Externally publishedYes

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