Developmental regulation of Ca2+ and K+ currents during hormone-induced maturation of starfish oocytes.
AUTOR(ES)
Moody, W J
RESUMO
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.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=393981Documentos Relacionados
- Transforming ras proteins accelerate hormone-induced maturation and stimulate cyclic AMP phosphodiesterase in Xenopus oocytes.
- Gonadotropin-releasing hormone-induced Ca2+ transients in single identified gonadotropes require both intracellular Ca2+ mobilization and Ca2+ influx.
- Growth hormone receptor C-terminal domains required for growth hormone-induced intracellular free Ca2+ oscillations and gene transcription.
- Co-ordinated modulation of Ca2+ and K+ currents during ascidian muscle development.
- Ribonucleic Acid Synthesis by Cucumber Chromatin: Developmental and Hormone-induced Changes 1