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KMID : 0811720000040050403
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Korean Journal of Physiology & Pharmacology
2000 Volume.4 No. 5 p.403 ~ p.408
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Stationary Outward and Transient Ca2 -Dependent Currents in Hamster Oocytes
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Seong-Geun Hong/Yang-Mi Kim†
Jae-Hee Han/Jong-Su Kim/Seong-Geun Hong
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Abstract
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The outward currents elicited in hamster eggs by depolarizing pulses were studied. The currents appeared to comprise at least two components, a transient outward component (Ito) and a steady-state outward component (I∞).Ito was transiently followed by the cessation of inward Ca2+ current (ICa), and its current-voltage (I-V) relation was a mirror image of that of (ICa). Either blockade of (ICa) by Co2+ or replacement of Ca2+ with Sr2+ abolished Ito without change in I∞. Intracellular EGTA (10 mM) inhibited Ito but not I∞. suggesting strongly that generation of Ito requires intracellular Ca2+. Apamin (1 nM) abolished selectively Ito, indicatingthat Ito is Ca2+?dependentK+ current. On the other hand, I∞ was Ca2+?independent. Both Ito and I∞ were completely inhibited by internal Cs+ and external TEA. The estimated reversal potential of Ito was close to the theoretical EK. Taken together, both outward currents were carried by K+ channels. From these results, Ito is likely to be a current responsible for the hyperpolarizing responses seen in hamster eggs at fertilization.
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KEYWORD
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K currents, Ca2 -dependent K current, Whole-cell current, Hamster oocytes,
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