Linked Life Data

12177187

Source:http://linkedlifedata.com/resource/pubmed/id/12177187

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
16
pubmed:dateCreated
2002-8-14
pubmed:abstractText
Two different families of Na+/Ca2+ exchangers, K+-independent NCX and K+-dependent NCKX, are known. Exploiting the outward K+ gradient, NCKX is able to extrude Ca2+ more efficiently than NCX, even when the Na+ gradient is reduced. The NCKX, which was originally thought to be limited to the retinal photoreceptor, was shown recently to be widely distributed in the brain. We investigated the contribution of Na+/Ca2+ exchange to Ca2+ clearance mechanisms in neurohypophysial (NHP) axon terminals, using patch-clamp and microfluorometry techniques. In the presence of internal K+, Ca2+ decay was significantly slowed by the removal of external Na+, indicative of the role of Na+/Ca2+ exchange. As internal [K+] was decreased, Ca2+ decay rate and its dependence on Na+ were greatly attenuated. In the absence of internal K+, Ca2+ decay rate was little affected by Na+ removal. Quantitative analysis using Ca2+ decay rate constant indicated that >60% of Ca2+ extrusion is mediated by Na+/Ca2+ exchange when peak [Ca2+] level is higher than 500 nm, and approximately 90% of Na+/Ca2+ exchange activity is K+ dependent. In situ hybridization confirmed the expression of NCKX2 transcripts in the supraoptic nucleus in which soma of NHP axon terminals are located. To our knowledge, this is the first report to show the significant role of K+-dependent Na+/Ca2+ exchange in neuronal cells other than photoreceptors. Considering that axon terminals are subject to an invasion by high-frequency Na+ spikes, which may lower Na+ gradients, the presence of NCKX may have a functional significance in intracellular Ca2+ regulation.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Aug
pubmed:issn
1529-2401
pubmed:author
pubmed:issnType
Electronic
pubmed:day
15
pubmed:volume
22
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
6891-9
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
2002
pubmed:articleTitle
K+-dependent Na+/Ca2+ exchange is a major Ca2+ clearance mechanism in axon terminals of rat neurohypophysis.
pubmed:affiliation
Department of Physiology and National Research Laboratory for Cellular Signaling, Seoul National University College of Medicine, Chongno-Ku, Seoul, 110-799, Korea.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't