Abstract
A calcium-activated non-selective cation channel was observed in isolated plasma membrane patches from an insulin-secreting cell line (CRI-Gl). The conductance of the channel was approximately 25 pS with identical (140 mM KCl) solutions on either side of the membrane. However, some rectification was observed (smaller outward current) when sodium ions were present extracellularly. The channel was inactive on exposure to an intracellular calcium concentration of 10(-6) M and required high (greater than 10(-4) M) concentrations for a significant degree of activation. The open-state probability of the channel was voltage dependent, increasing with membrane depolarization. Analysis of single channel kinetics indicated that there were at least two open and two closed states. Application of ATP to the cytoplasmic membrane surface reduced the open state probability in a dose-dependent manner. The channel activity was blocked by quinine and 4-AP but was insensitive to TEA, TTX and amiloride. It is not clear what role this channel might play in the complex electrical activity of ß-cells.
Original language | English |
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Pages (from-to) | 607-615 |
Number of pages | 9 |
Journal | Pflugers Archiv-European Journal of Physiology |
Volume | 409 |
Issue number | 6 |
Publication status | Published - Aug 1987 |
Keywords
- Animals
- Calcium
- Quinine
- Insulinoma
- Ion Channels
- Adenoma, Islet Cell
- Aminopyridines
- Rats
- Cations
- Kinetics
- Membrane Potentials
- 4-Aminopyridine
- Adenosine Triphosphate
- Cell Line