Korean J Physiol Pharmacol.  2000 Oct;4(5):403-408.

Stationary outward and transient Ca2+-dependent currents in hamster oocytes

• Kim YM
• Han JH
• Kim JS
• Hong SG

Abstract

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 (Iinfin). 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 Iinfin. Intracellular EGTA (10 mM) inhibited Ito but not Iinfin. suggesting strongly that generation of Ito requires intracellular Ca2+. Apamin (1 nM) abolished selectively Ito, indicating that Ito is Ca2+-dependent K+ current. On the other hand, Iinfin was Ca2+-independent. Both Ito and Iinfin 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.

Keyword

K currents; Ca2 -dependent K current; Whole-cell current; Hamster oocytes

MeSH Terms

Animals
Apamin
Cricetinae*
Eggs
Egtazic Acid
Fertilization
Hand
Oocytes*
Ovum
Tea
Apamin
Egtazic Acid
Tea