Open AccessDevelopmental regulation of Ca2+ and K+ currents during hormone-induced maturation of starfish oocytes.
Author(s) -
William J. Moody,
Jeffry B. Lansman
Publication year - 1983
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.80.10.3096
Subject(s) - oocyte , starfish , human fertilization , biophysics , chemistry , voltage clamp , hormone , endocrinology , biology , meiosis , electrophysiology , membrane potential , microbiology and biotechnology , medicine , anatomy , biochemistry , embryo , neuroscience , ecology , gene
Changes in the electrical properties of starfish oocytes during hormone-induced maturation (the reinitiation of meiosis prior to fertilization) were studied by using the voltage-clamp technique. Three voltage-dependent ionic currents dominate the current-voltage relation of the immature oocyte: an inward Ca2+ current, a fast transient K+ current similar to the "A current" of molluscan neurons, and an inwardly rectifying K+ current. During in vitro maturation stimulated by the natural maturing hormone 1-methyladenine, gradual changes in the amplitudes of all three currents were seen: the Ca2+ currents became larger, and both K+ currents became smaller. The kinetics of the currents were not significantly altered during maturation. As a result of these changes, action potentials in the mature egg had lower thresholds, faster rates of rise, and larger overshoots than those of the immature oocyte. We also found that the total membrane capacitance decreased substantially during maturation, perhaps indicating a decrease in membrane surface area triggered by the hormone. The significance of these results is discussed in terms of the preparation of the immature oocyte for fertilization and the mechanisms of modification of ion channel properties during development.