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Regulation of the fertilization current in ascidian oocytes by intracellular second messengers
Author(s) -
Tosti Elisabetta,
Dale Brian
Publication year - 1994
Publication title -
molecular reproduction and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 105
eISSN - 1098-2795
pISSN - 1040-452X
DOI - 10.1002/mrd.1080370416
Subject(s) - second messenger system , human fertilization , intracellular , biology , oocyte activation , egta , oocyte , microbiology and biotechnology , calcium , biophysics , calcium in biology , medicine , anatomy , embryo
Neomycin, injected into ascidian oocytes to a final concentration of 10–50 mM, inhibits both the fertilization current and the surface contraction, showing that phosphoinositide hydrolysis is required for these early activation events. Sperm‐activated fertilization currents are not inhibited in the presence of 100 μg/ml intracellular heparin, suggesting that these currents are not directly gated by InsP 3 . The sulfhydryl reagent thimerosal at 100 μM, in contrast, significantly increases the fertilization current presumably by sensitizing the channel receptor. Since heparin inhibits the surface contraction, InsP 3 receptors are shown to play a role in the propagation of the activation response in ascidian oocyte. Depleting intracellular calcium stores by microinjecting 50 mM EGTA into oocytes does not activate fertilization channels; however, subsequent fertilization of these EGTA loaded oocytes leads to a significantly larger and faster fertilization current. Thus in contrast to somatic cells studied to date, second messenger operated plasma membrane channels in ascidian oocytes are not gated by calcium released from intracellular stores. © 1994 Wiley‐Liss, Inc.