Referenced in: none

Automatically associated channels: Kir1.1 , Kir4.1

Title: Calcium influx mediated by the inwardly rectifying K+ channel Kir4.1 (KCNJ10) at low external K+ concentration.

Authors: Kai Härtel, Karthika Singaravelu, Melanie Kaiser, Clemens Neusch, Swen Hülsmann, Joachim W Deitmer

Journal, date & volume: Cell Calcium, 2007 Sep , 42, 271-80

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/17284334

Abstract
COS-1 cells with heterologeous expression of the Kir4.1 (KCNJ10) channel subunit, possess functional Kir4.1 channels and become capable to generating cytosolic Ca2+ transients, upon lowering of the extracellular K+ concentration to 2 mM or below. These Ca2+ transients are blocked by external Ba2+ (100 microM). Acute brain stem slices from wild-type mice (second post-natal week), which were loaded with the fluorescent Ca2+ indicator Oregon Green BAPTA-1-AM, were exposed to 0.2 mM K+. Under these conditions astrocytes, but not neurons, responded with cytosolic Ca2+ elevations in wild-type mice. This astrocyte-specific response has previously been used to identify astroglial cells type [R. Dallwig, H. Vitten, J.W. Deitmer, A novel barium-sensitive calcium influx into rat astrocytes at low external potassium. Cell Calcium 28 (2000) 247-259]. In Kir4.1 knock-out (Kir4.1-/-) mice, the number of responding cells was dramatically reduced and the Ca2+ transients in responding cells were significantly smaller than in wild-type mice. Our results indicate that Kir4.1 channels are the molecular substrate for the observed Ca2+ influx in astrocytes under conditions of low external K+-concentration.