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A Ca(2+)-activated Cl- current in sheep parotid secretory cells
1Department of Physiology, University of Sydney, N.S.W., Australia.
The Journal of Membrane Biology
|September 1, 1993
Summary
This study identifies a calcium-activated chloride (Cl-) channel in sheep parotid cells. This channel exhibits outward rectification and is permeable to various anions, offering new insights into salivary gland ion transport.
Area of Science:
- Cellular Physiology
- Ion Transport Mechanisms
- Salivary Gland Function
Background:
- Sheep parotid cells possess dominant K+ conductances affecting their electrical properties.
- Understanding alternative ion conductances is crucial for comprehending cell function.
Purpose of the Study:
- To characterize a residual ion conductance in sheep parotid cells after blocking K+ channels.
- To determine the ion selectivity, activation properties, and blockers of this conductance.
Main Methods:
- Whole-cell patch-clamp electrophysiology was used to record currents.
- Ion substitution experiments in the pipette and bath solutions identified Cl- selectivity.
- Calcium concentration in the pipette solution was manipulated to assess activation.
- Anion substitution and blocker application were employed to study permeability and inhibition.
Main Results:
- A Ca2+-activated, outwardly rectifying Cl- conductance was identified.
- The channel demonstrated significant permeability to SCN-, I-, and Cl-.
- Current activation was dependent on membrane depolarization and intracellular Ca2+ levels.
- Specific blockers like NPPB, DIDS, and furosemide inhibited the Cl- current.
Conclusions:
- Sheep parotid cells possess a distinct Ca2+-activated Cl- channel.
- This channel plays a role in regulating cell excitability and fluid secretion.
- The channel's properties provide a target for pharmacological modulation.