Three distinct chloride channels control anion movements in rat parotid acinar cells.
1. We used the whole-cell configuration of the patch clamp technique to examine the different macroscopic Cl- currents present in single rat parotid acinar cells. 2. Cell swelling produced by negative osmotic pressure (hypotonic bath solutions) induced a large outwardly rectifying Cl- current with little or no time and voltage dependence. In contrast, an increase in intracellular [Ca2+] induced by ionomycin activated Cl- currents with very different properties. Ca(2+)-activated Cl- currents showed outward rectification, relatively slow activation kinetics and marked voltage dependence. These results are consistent with the existence of two different outwardly rectifying Cl- channels in rat parotid cells. 3. In conditions designed to eliminate the activation of these two Cl- currents, a third type of current was observed. This third current was activated in a time-dependent manner by hyperpolarized potentials and was about equally permeant to Cl-, I- and Br-. 4. The properties of the hyperpolarization-activated current were similar to those of the cloned ClC-2 channel. Polymerase chain reaction-based methods and ribonuclease protection analyses indicated the presence in parotid gland of mRNA homologous to ClC-2. 5. Individual parotid acinar cells expressed all three types of Cl- channels. Each type of channel may contribute to Cl- efflux in distinct stages of the secretion process depending on the intracellular [Ca2+], cell volume and membrane potential.
Arreola
J
J
Department of Dental Research, University of Rochester Medical Center, NY 14642, USA.
Park
K
K
Melvin
J E
JE
Begenisich
T
T
D000818:Animals; D000838:Anions / Q000378:metabolism*; D001483:Base Sequence; D002118:Calcium / Q000494:pharmacology; D018118:Chloride Channels / Q000378:metabolism*; D017931:DNA Primers / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D004594:Electrophysiology; D066298:In Vitro Techniques; D008297:Male; D008969:Molecular Sequence Data; D009997:Osmotic Pressure; D010306:Parotid Gland / Q000166:cytology / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D016133:Polymerase Chain Reaction; D016372:RNA, Antisense; D051381:Rats; D017208:Rats, Wistar; D012260:Ribonucleases / Q000378:metabolism
D000838:Anions; D018118:Chloride Channels; D017931:DNA Primers; D016372:RNA, Antisense; D012260:Ribonucleases; D002118:Calcium