Three distinct chloride channels control anion movements in rat parotid acinar cells.
1996; Wiley; Volume: 490; Issue: 2 Linguagem: Inglês
10.1113/jphysiol.1996.sp021149
ISSN1469-7793
AutoresJorge Arreola, Kyoungsook Park, James E. Melvin, Ted Begenisich,
Tópico(s)Ion Transport and Channel Regulation
Resumo1. 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.
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