Regulation of cation-selective channels in liver cells.
In liver cells, cation-selective channels are permeable to Ca2+ and have been postulated to represent a pathway for receptor-mediated Ca2+ influx. This study examines the mechanisms involved in the regulation of these channels in a model liver cell line. Using patch-clamp recording techniques, it is shown that channel open probability is a saturable function of cytosolic [Ca2+], with half-maximal opening at 660 nm. By contrast, channel opening is not affected by membrane voltage or cytosolic pH. In intact cells, reduction of cytosolic [Cl-], a physiological response to Ca2+-mobilizing hormones and cell swelling, is also associated with an increase in channel opening. Finally, channel opening is inhibited by intracellular ATP through a mechanism that does not involve ATP hydrolysis. These findings suggest that opening of cation-selective channels is coupled to the metabolic state of the cell and provides a positive feedback mechanism for regulation of receptor-mediated Na+ and Ca2+ influx.
Lidofsky
S D
SD
Department of Medicine and the Liver Center, University of California, San Francisco, CA 94143, USA.
Sostman
A
A
Fitz
J G
JG
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D007473:Ion Channels / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D051381:Rats; D014407:Tumor Cells, Cultured
D007473:Ion Channels; D002118:Calcium