Sensitivity to dihydropyridines, ?-conotoxin and noradrenaline reveals multiple high-voltage-activated Ca2+ channels in rat insulinoma and human pancreatic ?-cells

Pollo, Antonella; Lovallo, Michele; Biancardi, E.; Sher, Emanuele; Socci, C.; Carbone, Emilio

doi:10.1007/bf00374942

Cited by 60 publications

(61 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…4). This Ca-id was sensitive to relatively high NDP concentrations (25 HM) that block L-type [32] or even T-type Ca 2+ channels [33], consistent with the presence of voltage-dependent Ca 2+ channels in mammalian sperm [9]. T-type Ca 2+ channels have been described in spermatogenic cells [34].…”

Section: Discussionsupporting

confidence: 60%

Mouse sperm membrane potential: changes induced by Ca²⁺

Espinosa

Darszon

1995

FEBS Letters

View full text Add to dashboard Cite

Section: Discussionsupporting

confidence: 60%

Mouse sperm membrane potential: changes induced by Ca²⁺

Espinosa

Darszon

1995

FEBS Letters

View full text Add to dashboard Cite

“…As expected from previous whole-cell recordings [18,25], RINm5F cells express two pharmacologically distinct DHP-resistant channels: one sensitive toCTx-GVIA (N-type) and one insensitive to the toxin (non-L-, non-N-type, namely Q-like). Evidence for the existence of two non-L-type channels is mainly based on the irreversible block of Ca 2+ channels by -CTx-GVIA in isolated patches.…”

Section: Discussionsupporting

confidence: 80%

“…1A 1 ) nor in the current recordings during step depolarizations above 930 mV (Fig. 1A [25], the L-type current activates at slightly more negative potentials with respect to the non-L-, non-N-type current (¡ and solid line). Halfmaximal activation (V ½ ) of the L-type current was around 92 mV compared to the + 6 mV of the non-L-, non-N-type component.…”

Section: Discussionmentioning

confidence: 86%

“…The activity of the Q-like channel is strongly depressed at low holding potentials ( 950 mV) while the L-type persists at these values [28]. The channel inactivates little and very slowly irrespective of whether it is recorded in the cell-attached or outside-out configuration, suggesting a marked insensitivity to intracellular Ca 2+ buffers and a marginal role of Ca 2+ in the regulation of the channel inactivation gate [20,25]. In contrast, L-type channels of insulin-secreting cells exhibit marked Ca 2+ -dependent inactivation properties [20,22,25].…”

Section: Discussionmentioning

confidence: 99%

“…The latter contributes to most of the Ca 2+ current and is ubiquitous in all insulin-secreting cells [2]. Recent reports, however, have provided increasing evidence for the existence, in -cells and -cell lines, of a significant DHP-resistant HVA current component [13,25] that is partially blocked by -CTx-GVIA [31] and modulated by noradrenaline [25]. Electrophysiological [18] and molecular biology studies [15] have also provided evidence for the existence in rat islets and RINm5F cells of a class A Ca 2+ channel (Q-, or P-type) that is resistant to DHP, -CTx-GVIA and high doses of -agatoxin-IVA ( -Aga-IVA), but is sensitive to micromolar concentrations of -CTx-MVIIC.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A single non-L-, non-N-type Ca2+ channel in rat insulin-secreting RINm5F cells

Magnelli¹,

Avaltroni²,

Carbone³

1996

Pflugers Arch.

Self Cite

View full text Add to dashboard Cite

Single high-voltage-activated (HVA) Ca 2+ channel activity was recorded in rat insulinoma RINm5F cells using cell-attached and outside-out configurations. Single-channel recordings revealed three distinct Ca 2+ channel subtypes : one sensitive to dihydropyridines (DHPs)-(L-type), another sensitive to -conotoxin (CTx)-GVIA (N-type) and a third type insensitive to DHPs and -CTx-GVIA (non-L-, non-N-type). The L-type channel was recorded in most patches between 930 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 µM Bay K 8644). The non-L-, non-N-type channel was recorded in cells chronically treated with -CTx-GVIA in the presence of nifedipine to avoid the contribution of N-and L-type channels. Channel activity was hardly detectable below 910 mV and was recruited by negative holding potentials (< 990 mV). The channel open probability increased steeply from 910 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 300-800 ms with little sign of inactivation. Above 0 mV the channel showed a persistent flickering kinetics with brief openings ( o 0.6 ms) and long bursts ( burst 60 ms) interrupted by short interburst intervals. The third HVA Ca 2+ 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 -CTx-GVIA. The channel was detectable only above 910 mV from a 990 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 Ca 2+ channels in cellattached and excised membrane patches under controlled pharmacological conditions.

show abstract