Changes in membrane potential during mouse egg development |
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Authors: | M H Cross P C Cross R L Brinster |
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Affiliation: | Laboratory of Reproductive Physiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19174 USA |
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Abstract: | The electrical membrane potential (Em) was measured in the developing mouse egg with intracellular microelectrodes. The oocyte had a low negative Em of ?8.3 ± 0.8 mV (mean ± SE) when immature, which decreased and reversed polarity to a small positive value (+1.9 ± 0.2 mV) in the mature ovulated oocyte. After fertilization Em returned to a negative value (?9.2 ± 0.5 mV) similar in magnitude to that observed in immature oocytes and then increased significantly (P < 0.01) at both the two-cell (?10.7 ± 0.3 mV) and morula stage (?12.8 ± 0.7 mV) and leveled out at the blastocyst stage (?12.9 ± 0.7 mV). Average potential difference recorded across the blastocoele wall of not fully expanded blastocysts was ?5.0 ± 0.5 mV. These data represent the first report on membrane potentials of the mammalian egg during development. A striking similarity is seen in the relative changes in Em throughout development of the mouse egg in comparison to those seen in other invertebrate and vertebrate eggs. |
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