Oxidative phosphorylation-linked respiration in individual bovine oocytes.
Mitochondrial bioenergetics in mammalian oocytes has not been sufficiently characterized. In this study, the function of oxidative phosphorylation (OXPHOS), a major pathway in mitochondria, was investigated in individual bovine oocytes by monitoring oxygen consumption using modified scanning electrochemical microscopy (SECM). At the germinal vesicle (GV) stage, 65% of basal respiration was used for mitochondrial respiration, which was inhibited by complex IV inhibitor. Around 63% of mitochondrial respiration was coupled to ATP synthesis, as determined by sensitivity to an ATP synthase inhibitor, and the remaining 37% was attributed to proton leak. In contrast, 50% and 43% of mitochondrial respiration were used for ATP synthesis in in vivo- and in vitro-derived metaphase II (MII)-stage oocytes, respectively. ATP-linked respiration, in both in vivo- and in vitro-derived MII-stage oocytes, was significantly lower than in GV-stage oocytes, suggesting that OXPHOS in bovine oocytes is more active at the GV stage compared with the MII stage. Interestingly, basal respiration in in vitro-derived MII oocytes was significantly higher than for in vivo-derived oocytes, reflecting an increase in proton leak. Next, we assessed respiration in MII oocytes cultured for 8 h. The aged oocytes had a significantly reduced maximum respiratory capacity, which was stimulated by a mitochondrial uncoupler, and reduced ATP-linked respiration compared with non-aged oocytes. However, the aging-related phenomenon could be prevented by caffeine treatment. We conclude that OXPHOS in bovine oocytes varies in the transition from GV to MII stage, in vitro maturation and the aging process. This approach will be particularly useful for analyzing mitochondrial bioenergetics in individual mammalian oocytes.
National Livestock Breeding Center, Fukushima 961-8511, Japan.
Satoshi
S
Sugimura
Satoko
S
Matoba
Yutaka
Y
Hashiyada
Yoshio
Y
Aikawa
Masaki
M
Ohtake
Hideo
H
Matsuda
Shuji
S
Kobayashi
Kazuyuki
K
Konishi
Kei
K
Imai
D000255:Adenosine Triphosphate / Q000378:metabolism; D000375:Aging / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002417:Cattle; D019069:Cell Respiration; D005260:Female; D008928:Mitochondria / Q000378:metabolism*; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism*; D010085:Oxidative Phosphorylation; D010101:Oxygen Consumption; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology
D010726:Phosphodiesterase Inhibitors; D002110:Caffeine; D000255:Adenosine Triphosphate