These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: A single non-L-, non-N-type Ca2+ channel in rat insulin-secreting RINm5F cells.
    Author: Magnelli V, Avaltroni A, Carbone E.
    Journal: Pflugers Arch; 1996 Jan; 431(3):341-52. PubMed ID: 8584427.
    Abstract:
    Single high-voltage-activated (HVA) Ca2+ channel activity was recorded in rat insulinoma RINm5F cells using cell-attached and outside-out configurations. Single-channel recordings revealed three distinct Ca2+ channel subtypes: one sensitive to dihydropyridines (DHPs)-(L-type), another sensitive to omega -conotoxin (CTx)-GVIA (N-type) and a third type insensitive to DHPs and omega -CTx-GVIA (non-L-, non-N-type). The L-type channel was recorded in most patches between -30 and +30 mV. The channel had pharmacological and biophysical features similar to the L-type channels described in other insulin-secreting cells (mean conductance 21 pS in control conditions and 24 pS in the presence of 5 microM Bay K 8644). The non-L-, non-N-type channel was recorded in cells chronically treated with omega -CTx-GVIA in the presence of nifedipine to avoid the contribution of N- and L-type channels. Channel activity was hardly detectable below -10 mV and was recruited by negative holding potentials (< -90 mV). The channel open probability increased steeply from -10 to + 40 mV. Different unitary current sublevels could be detected and the current voltage relationship was calculated from the higher amplitude level with a slope conductance of 21 pS. Channel activity lasted throughout depolarizations of 300-800ms with little sign of inactivation. Above 0 mV the channel showed a persistent flickering kinetics with brief openings (tau o 0.6 ms) and long bursts (tau burst 60 ms) interrupted by short interburst intervals. The third HVA Ca2+ channel subtype, the N-type, had biophysical properties similar to the non-L-, non-N-type and was best identified in outside-out patches by its sensitivity to omega -CTx-GVIA. The channel was detectable only above -10 mV from a -90 mV holding potential, exhibited a fast flickering behaviour, persisted during prolonged depolarizations and had a slope conductance of about 19 pS. The present data provide direct evidence for a slowly inactivating non-L-, non-N-type channel in insulin-secreting RINm5F cells that activates at more positive voltages than the L-type channel and indicate the possibility of identifying unequivocally single HVA Ca2+ channels in cell-attached and excised membrane patches under controlled pharmacological conditions.
    [Abstract] [Full Text] [Related] [New Search]