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Kinetics and regulation of a Ca2+-activated Cl- conductance in mouse renal inner medullary collecting duct cells

Lookup NU author(s): Dr Stefan Boese, Omar Aziz, Professor Nicholas Simmons, Dr Michael Gray


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Using the whole cell patch-clamp technique, a Ca2+-activated Cl- conductance (CaCC) was transiently activated by extracellular ATP (100 μM) in primary cultures of mouse inner medullary collecting duct (IMCD) cells and in the mouse IMCD-K2 cell line. ATP also transiently increased intracellular Ca2+ concentration ([Ca2+]i) from ∼100 nM to peak values of ∼750 nM in mIMCD-K2 cells, with a time course similar to the ATP-induced activation and decay of the CaCC. Removal of extracellular Ca2+ had no major effect on the peak Cl- conductance or the increase in [Ca2+]i induced by ATP, suggesting that Ca2+ released from intracellular stores directly activates the CaCC. In mIMCD-K2 cells, a rectifying time- and voltage-dependent current was observed when [Ca2+]i was fixed via the patch pipette to between 100 and 500 nM. Maximal activation occurred at ∼1 μM [Ca2+]i, with currents losing any kinetics and displaying a linear current-voltage relationship. From Ca2+-dose-response curves, an EC50 value of ∼650 nM at ∼80 mV was obtained, suggesting that under physiological conditions the CaCC would be near fully activated by mucosal nucleotides. Noise analysis of whole cell currents in mIMCD-K2 cells suggests a single-channel conductance of 6-8 pS and a density of ∼5,000 channels/cell. In conclusion, the CaCC in mouse IMCD cells is a low-conductance, nucleotide-sensitive Cl- channel, whose activity is tightly coupled to changes in [Ca2+]i over the normal physiological range.

Publication metadata

Author(s): Boese SH, Aziz O, Simmons NL, Gray MA

Publication type: Article

Publication status: Published

Journal: American Journal of Physiology - Renal Physiology

Year: 2004

Volume: 286

Issue: 4

Pages: F682-F692

ISSN (print): 0363-6127

ISSN (electronic): 1522-1466

Publisher: American Physiological Society


DOI: 10.1152/ajprenal.00123.2003

PubMed id: 14678946


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