Linked Life Data

1880791

Source:http://linkedlifedata.com/resource/pubmed/id/1880791

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
2
pubmed:dateCreated
1991-9-27
pubmed:abstractText
To investigate the voltage dependence of the Na+/K+ pump, current-voltage relations were determined in prophase-arrested oocytes of Xenopus laevis. All solutions contained 5 mM Ba2+ and 20 mM tetraethylammonium (TEA) to block K+ channels. If, in addition, the Na+/K+ pump is blocked by ouabain, K(+)-sensitive currents no larger than 50 nA/cm2 remain. Reductions in steady-state current (on the order of 700 nA/cm2) produced by 50 microM ouabain or dihydro-ouabain or by K+ removal, therefore, primarily represent current generated by the Na+/K+ pump. In Na(+)-free solution containing 5 mM K+, Na+/K+ pump current is relatively voltage independent over the potential range from -160 to +40 mV. If external [K+] is reduced below 0.5 mM, negative slopes are observed over this entire voltage range. Similar results are seen in Na(+)- and Ca(2+)-free solutions in the presence of 2 mM Ni2+, an experimental condition designed to prevent Na+/Ca2+ exchange. The occurrence of a negative slope can be explained by the voltage dependence of the apparent affinity for activation of the Na+/K+ pump by external K+, consistent with the existence of an external ion well for K+ binding. In 90 mM Na+, 5 mM K+ solution, Na+/K+ pump current-voltage curves at negative membrane potentials have a positive slope and can be described by a monotonically increasing sigmoidal function. At an extracellular [K+] of 1.3 mM, a negative slope was observed at positive potentials. These findings suggest that in addition to a voltage-dependent step associated with Na+ translocation, a second voltage-dependent step that is dependent on external [K+], possibly external K+ binding, participates in the overall reaction mechanism of the Na+/K+ pump.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Apr
pubmed:issn
0022-2631
pubmed:author
pubmed:issnType
Print
pubmed:volume
121
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
177-87
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1991
pubmed:articleTitle
A negative slope in the current-voltage relationship of the Na+/K+ pump in Xenopus oocytes produced by reduction of external [K+].
pubmed:affiliation
Max-Planck-Institut für Biophysik, Frankfurt am Main, Federal Republic of Germany.
pubmed:publicationType
Journal Article, In Vitro, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't