Stationary outward and transient Ca2+-dependent currents in hamster oocytes.
- Author:
Yang Mi KIM
1
;
Jae Hee HAN
;
Jong Su KIM
;
Seong Geun HONG
Author Information
1. Department of Physiology, Gyeongsang National University College of Medicine, 90 Chilam-Dong, Chinju, South Korea. hong149@gshp.gsnu.ac.kr
- Publication Type:Original Article
- Keywords:
K currents;
Ca2 -dependent K current;
Whole-cell current;
Hamster oocytes
- MeSH:
Animals;
Apamin;
Cricetinae*;
Eggs;
Egtazic Acid;
Fertilization;
Hand;
Oocytes*;
Ovum;
Tea
- From:The Korean Journal of Physiology and Pharmacology
2000;4(5):403-408
- CountryRepublic of Korea
- Language:English
-
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.
