Oxygen Consumption of Maturing Rat Oocytes

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Abstract
The oxygen consumption of isolated, mechanically denuded rat occytes in different stages of meiosis was analyzed by a highly sensitive microspectrophotometric technique. The oocytes were either induced to mature in vivo by LH or matured spontaneously when cultured. In both cases there was a gradual increase in respiration of the oocytes following the onset of morphological nuclear maturation. When oocytes were isolated from preovulatory follicles after LH injection the respiration of maturing oocytes with germinal vesicle breakdown (GVB) was 0.173 ± 0.005 nl O2/h/oocyte (n=25). This is significantly higher than the respiration of dictyate oocytes taken from rats not treated with LH, which was 0.135 ± 0.003 nl O2/h/oocyte (n=38). Oocytes with polar body (PB) consumed 0.206 ± 0.007 nl O2/h/oocyte (n=14) and oocytes recovered from the oviduct after ovulation consumed 0.203 ± 0.004 nl O2/h/oocyte (n=7). For oocytes maturing spontaneously in culture the oxygen consumption was 0.171 ± 0.004 nl O2/h/oocyte (n=33) (oocytes with GVB) and 0.190 ± 0.013 nl O2/h/oocyte (n=4) (oocytes with PB), in both cases a significant increase as compared to control, i.e., not cultured oocytes, which consumed 0.142 ± 0.003 nl O2/h/oocyte (n=18). Neither after LH injection nor after cultivation was the respiration of oocytes still containing germinal vesicle different from control. It is concluded that the resumption of oocyte meiosis is accompanied by an increase in oxygen consumption and that this increase seems to be related to the meiotic process rather than to hormonal stimulation.