Linked Life Data

6304316

Source:http://linkedlifedata.com/resource/pubmed/id/6304316

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1-2
pubmed:dateCreated
1983-7-29
pubmed:abstractText
Calcium ions affect the gating of Ca currents. Surface charge is involved but to what extent is unknown. We have examined this, using isolated nerve cell bodies of Helix aspersa and the combined microelectrode-suction pipette method for voltage-clamp and internal perfusion. We found that Ba and Sr currents produced by substitution of these ions for extracellular Ca ions are activated at less positive potentials than Ca currents. Mg ions do not permeate the Ca channel and changes in [Mg]o produce shifts in the activation-potential curves that are comparable to the effects of changes in [Ba]o or [Sr]o. Inactivation of Ba currents also occurs at less positive potentials. Perfusion intracellularly with EGTA reduced inactivation of Ca currents as a function of potential, but did not shift the inactivation-potential curve. Hence, Ca current-dependent inactivation which is blocked by intracellular EGTA probably does not involve a similar change of intracellular surface potential. The voltage shifts of activation and inactivation produced by extracellular divalent cations used singly or in mixtures can be described by the Gouy-Chapman theory for the diffuse double layer with binding (Gilbert & Ehrenstein, 1969; McLaughlin, Szabo & Eisenman, 1971). From the surface potential values and the Boltzman distribution, we have computed surface concentrations that predict the following experimental observations: 1) saturation of current-concentration relationships when surface potential is changing maximally; 2) the increase in peak current when Ca ions are replaced by Sr or Ba ions; and 3) the greater inhibitory effect of Mg on IBa than ICa. Theory indicates that surface charge cannot be screened completely even at 1 M [Mg]o and thus that Ca channel properties must be evaluated in the light of surface charge effects. For example, after correction for surface charge effects the relative permeabilities of Ca, Ba and Sr ions are equivalent. In the presence of Co ions, however, Ca ions are more permeable than Ba ions suggesting a channel binding site may be involved.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:issn
0022-2631
pubmed:author
pubmed:issnType
Print
pubmed:volume
72
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
117-30
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1983
pubmed:articleTitle
Interaction between calcium ions and surface charge as it relates to calcium currents.
pubmed:publicationType
Journal Article, In Vitro, Research Support, U.S. Gov't, P.H.S.