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Requirement of Extracellular Calcium Ions for the Early Fertilization Events in the Medaka Egg
Author(s) -
IWAMATSU T.,
OHTA T.,
OSHIMA E.,
SUGIURA T.
Publication year - 1985
Publication title -
development, growth and differentiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.864
H-Index - 66
eISSN - 1440-169X
pISSN - 0012-1592
DOI - 10.1111/j.1440-169x.1985.00751.x
Subject(s) - human fertilization , calcium , extracellular , biology , zoology , chemistry , microbiology and biotechnology , anatomy , organic chemistry
The requirement for calcium and the change in calcium content in eggs of Oryzias iatipes during the cortical reaction and sperm penetration were examined. Naked eggs failed to exhibit the cortical reaction upon insemination under Ca Mg‐free conditions. These eggs exhibited the cortical reaction by reinsemination in the presence of extracellular Ca 2+ . The effect of extracellular Ca 2+ on sperm penetration could be replaced by one of several divalent cations in the external medium. Unlike the cortical reaction, sperm penetration failed to be induced by microinjection to increase intracellular Ca 2+ . Verapamil significantly reduced the action of extracellular Ca 2+ or Ba 2+ of divalent cations examined in fertilization, while TEA and TTX had no effect on fertilization in the presence of these cations. No 45 Ca uptake into the egg proper was recognized before completion of the cortical reaction. These observations suggest that extracellular divalent cations are indispensable for sperm stimulation of the egg and its penetration into the egg, for which an influx of Ca 2+ from the external medium is not required.