Open AccessCa-mediated activation of a K current at fertilization of golden hamster eggs.
Author(s) -
Shunichi Miyazaki,
Yukio Igusa
Publication year - 1982
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.79.3.931
Subject(s) - polyspermy , human fertilization , hamster , biophysics , membrane potential , intracellular , oocyte activation , egta , sperm , golden hamster , hyperpolarization (physics) , reversal potential , chemistry , conductance , biology , biochemistry , microbiology and biotechnology , calcium , anatomy , patch clamp , endocrinology , botany , oocyte , stereochemistry , embryo , receptor , mathematics , nuclear magnetic resonance spectroscopy , organic chemistry , combinatorics
Golden hamster eggs respond to fertilization with recurring hyperpolarizations [Miyazaki, S. & Igusa, Y. (1981) Nature (London) 290, 703-705]. We analyzed the ionic mechanism of the fertilization potential and examined whether the fertilization potential plays a role in polyspermy block. Each hyperpolarizing response (HR) during fertilization is found to be caused by an increase in the K conductance activated by an increase in the intracellular Ca2+ concentration. This conclusion is based on the following: (i) The reversal potential of the HR shifted with the Nernstian slope for K ions when the external K concentration was changed, whereas it was unaltered by the removal of Cl ions. (ii) The HR was blocked by the intracellular injection of EGTA. (iii) Injection of Ca2+ into an egg induced a hyperpolarization of the membrane similar to the HR. The Ca-activated K conductance shows an apparent outward rectification, which could be explained by an asymmetric distribution of K ions across the membrane. The HR associated with sperm entry into the egg occurred at any membrane potential between -160 and +50 mV. Therefore, a potential-dependent block of sperm entry does not occur in the hamster egg.