Transmembrane electropotential changes in amphibian eggs at ovulation, activation and first cleavage

✍ Scribed by Gene A. Morrill; Donald E. Watson

• Book ID: 102881764
• Publisher: John Wiley and Sons
• Year: 1966
• Tongue: English
• Weight: 676 KB
• Volume: 67
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1040670110

✦ Synopsis

Electropotential differences between the cell interior and the external medium have been studied with intracellular microelectrodes in ovarian oocytes, ovulated unfertilized eggs and fertilized eggs of R. pipiens. In ovarian oocytes the cytoplasm was 50 to 80 mV negative, relative to isotonic Ringer's solution. In contrast, electrode penetration of the oocyte nucleus i n situ indicated that the nucleoplasm was about 25 mV positive, relative to the cytoplasm. After ovulation, the cortical cytoplasm became 20 to 50 mV positive with regard to an external solution of 0.1 strength Ringer's solution (ca. pond water). Penetration of the cytoplasm at levels from 0.3 to 0.6 mm below the egg surface revealed an inner zone with a potential which was about 15 mV negative, relative to the cortical cytoplasm. A slow hyperpolarization of the cortical membrane occurred at activation, with the potential returning to that of the ovulated unfertilized egg within ten minutes. After fertilization, the egg cytoplasm remained positive until the first cleavage. As division proceeded, the cytoplasm slowly depolarized and became 50 to 60 mV negative, relative to 0.1 strength Ringer's solution.