A FUNCTIONAL VIEW OF THE ENTRANCES OF L-TYPE CA2+ CHANNELS - ESTIMATES OF THE SIZE AND SURFACE-POTENTIAL AT THE PORE MOUTHS

被引:33
作者
KUO, CC [1 ]
HESS, P [1 ]
机构
[1] HARVARD UNIV,SCH MED,DEPT CELLULAR & MOLEC PHYSIOL,PROGRAM NEUROSCI,BOSTON,MA 02115
关键词
D O I
10.1016/0896-6273(92)90189-K
中图分类号
Q189 [神经科学];
学科分类号
071006 ;
摘要
At extreme membrane potentials, the unitary inward and outward currents through L-type Ca2+ channels become diffusion controlled and saturate. The magnitudes of these currents indicate that the pore entrances are asymmetric, with the external mouth being much larger than the internal one. On the other hand, negative surface potentials at the two ends of the pore are rather similar. Both would be significant only when the ambient ionic strength is 110 mM or less. We conclude that the surface charges will not help much in concentrating the channel's favorite divalent cations in the physiological condition. However, the pore does possess an external mouth large enough to make the important inward Ca2+ flow not limited by diffusion, even with only 1 mM external Ca2+.
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页码:515 / 526
页数:12
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