|
KMID : 0358619940280020215
|
|
Korean Journal of Physiology
1994 Volume.28 No. 2 p.215 ~ p.224
|
|
|
Calcium Current in the Unfertilized Egg of the Hamster
|
|
Haan Jae-Hee
Cho Soo-Wan
Yang Young-Sun
Park Young-Geun
Park Hong-Gi
Chang Gyeong-Jae
Kim Yang-Mi
Park Choon-Ok
Hong Seong-Geun
|
|
|
Abstract
|
|
|
|
The presence of a calcium current passed via a specific channel was examined in the unfertilized hamster egg using the whole-cell voltage clamp technique. Pure inward current was isolated using a pipette solution containing 10 mM TEA. This current was independent of external and was highly sensitive to the concentration in the bathing solution, indicating that the inward current is carried by . The maximal amplitude was with 10mM at -3OmV from a holding potential of -8OmV. This current reached its maximum within 20ms beyond -3OmV and decayed rapidly with an inactivation time constant of 15ms. Activation and inactivation of this was steeply dependent on the membrane potential. The began to activate at the lower voltage of -55 mV and reached its peak at -35 mV, being completely inactivated at potentials more positive than -40 mV. These result suggest that in hamster eggs passes through channels with electrical properties similar to low voltage-activated T-type channels. Other results from the present study support this suggestion; First, the inhibitory effect of was more potent than . Second, conductance was equal to or below that of . Third, in hamster eggs was relatively insensitive to nifedipine , known to be a specific t-type blocker. The physiological role of in the unfertilized hamster eggs remains unclear. Analysis from steady-state inactivation activation curves reveals that only a small amount of this current will pass in the voltage range which partially overlaps with the resting membrane potential. This current has the property that it can be easily activated by a weak depolarization, thus it may trigger a certain kind of a intracellular event following fertilization which may cause oscillations in the membrane potential.
|
|
|
KEYWORD
|
|
|
Calcium current, T-type channel, Unfertilized hamster egg, Whole-cell voltage clamp technique
|
|
|
FullTexts / Linksout information
|
|
|
|
|
|
Listed journal information
|
|
|