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  • RINm5F cell  (6)
  • Membrane potential  (5)
  • 1
    Digitale Medien
    Digitale Medien
    ATP-sensitive K+ channels in an insulin-secreting cell line are inhibited byd-glyceraldehyde and activated by membrane permeabilization (1986)
    Springer
    The journal of membrane biology 93 (1986), S. 271-279 
    Details
    ISSN: 1432-1424
    Schlagwort(e): K+ channel ; ATP ; glyceraldehyde ; RINm5F cell
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary The control of K+ channels in the insulin-secreting cell line RINm5F has been investigated by patch-clamp singlechannel current recording experiments. The unitary current events recorded from cell-attached patches are due to large and small inwardly rectifying ATP-sensitive K+ channels with conductance properties similar to the two channels previously identified in primary cultured rat islet cells (Findlay, I., Dunne, M.J., & Petersen, O. H.J. Membrane Biol. 88:165–172, 1985). Cell permeabilization through brief exposure to 10 μm digitonin or 0.05% saponin (outside the isolated membrane patch area) results in a dramatic increase in current through the cell-attached patch due to opening of many large and small K+-selective channels. These channels are inhibited in a dose-dependent manner by ATP applied to the bath (near-complete inhibition by 5mm ATP). During prolonged ATP exposure (1–5 min) the initial inhibition is followed by partial recovery of channel activity, although further activation does occur when ATP is subsequently removed. From the maximal number of coincident channel openings in the permeabilized cells (in the absence of ATP), it is estimated that there are on average 12 large ATP-sensitive K+ channels per membrane patch, but in the intact cells less than 5% of the membrane patches exhibited three or more coincident K+ channel openings, indicating the degree to which the channels are inhibited in the resting condition by endogenous ATP. Stimulation of RINm5F cells to secrete insulin was carried out by challenging intact cells with 10mm d-glyceraldehyde.d-glyceraldehyde induced depolarization of the membrane from about −70 to −20 mV and evoked a marked reduction in the open-state probability of both the large and small ATP-sensitive channels.d-glyceraldehyde also induced action potentials in a number of cases. All effects of stimulation were largely transient, lasting about 100 sec. The two ATP-sensitive K+ channels are probably responsible for the resting potential and play a crucial role in coupling metabolism to membrane depolarization.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01871181
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  • 2
    Digitale Medien
    Digitale Medien
    Effects of intracellular EGTA injection on stimulant-evoked membrane potential and resistance changes in pancreatic acinar cells (1980)
    Springer
    Pflügers Archiv 386 (1980), S. 147-152 
    Details
    ISSN: 1432-2013
    Schlagwort(e): Pancreatic acinus ; Calcium ; Membrane potential ; Membrane resistance ; EGTA ; Stimulus-permeability coupling
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Membrane potential and resistance were measured from two neighbouring electrically coupled cells within the same mouse pancreatic acinus, using one electrode filled with KCl and another filled with K-EGTA [ethylene glycol-bis-(β-amino ethyl ether) N,N′-tetra acetic acid] or K-acetate. EGTA was injected into one cell by passing pulses of hyperpolarizing current through the EGTA microelectrode. In order to ensure constant membrane potential, pulses of depolarizing current of the same intensity were simultaneously passed through the other electrode. Intracellular injection of EGTA, but not acetate, decreased significantly the membrane response (depolarization, resistance reduction) of both coupled cells to small microionophoretic pulses of ACh stimulation. Responses to larger doses were decreased to a smaller extent. Intracellular injection of EGTA also decreased significantly the membrane response of both coupled cells to microionophoretic pulses of pentagastrin stimulation. In contrast intracellular injection of EGTA did not inhibit membrane response tol-alanine stimulation.l-Alanine-evoked membrane depolarization was independent of external Ca. This is in contrast to what has previously been shown for secretagogue effects. It is concluded that EGTA-induced sequestration of cytosolic Ca2+ decreases membrane responses to both ACh and pentagastrin, providing new evidence of the crucial role played by internal Ca2+ in mediating stimulus-permeability coupling. In contrast,l-alanine action does not appear to be mediated by internal Ca2+.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00584202
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  • 3
    Digitale Medien
    Digitale Medien
    Amino acid-evoked membrane potential and resistance changes in pancreatic acinar cells (1980)
    Springer
    Pflügers Archiv 386 (1980), S. 153-159 
    Details
    ISSN: 1432-2013
    Schlagwort(e): l-Amino acids ; Membrane potential ; Membrane resistance ; Pancreatic acinar cell ; Na-conductance ; l-Alanine-amino acid interactions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The effect of some neutrall-amino acids, alanine, valine and proline, on the pancreatic acinar cell membrane potential and resistance was investigated. Simultaneous recordings were made with two intracellular microelectrodes on isolated superfused segments of mouse pancreas. Amino acids were applied by inclusion at known concentrations in the superfusion fluid or by microionophoresis from extracellular micropipettes. l-Alanine (10 mmol·l−1) evoked a maximal membrane depolarization of about 18 mV. A just detectable depolarization was observed at 0.1 mmol·l−1 (3 mV). Halfmaximal depolarization was observed at 1.6 mmol·l−1.d-Alanine had virtually no effect. Microionophoretic applications ofl-alanine,l-valine orl-proline evoked depolarization and resistance reduction with a very short delay (〈50 ms). The dose response curves for depolarization and resistance reduction were similar. The amplitude of the depolarization evoked byl-alanine,l-valine andl-proline depended linearly on the level of the pre-set membrane potential (membrane potential could be changed by direct current injection). With decreasing intracellular negativity there was a decrease in the size of the amino acid-evoked depolarization. When the membrane potential was inside positive the amplitude became very small. Extrapolation of the linear relations between membrane potential and size of depolarization revealed a null potential of +20 to +45 mV. Thel-alanine-evoked depolarization was acutely reduced but not abolished by replacing extracellular Na by Tris or Li. l-Alanine,l-proline andl-valine exhibited mutual inhibition of evoked depolarization even when the depolarizing effect of the first applied amino acid was balanced by direct current injection. It is concluded that severall-amino acids act on the pancreatic acinar plasma membrane by opening conductance pathways mainly permeable to Na.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00584203
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  • 4
    Digitale Medien
    Digitale Medien
    Nervous control of membrane conductance in mouse lacrimal acinar cells (1984)
    Springer
    Pflügers Archiv 400 (1984), S. 51-59 
    Details
    ISSN: 1432-2013
    Schlagwort(e): Lacrimal acinar cell ; Membrane potential ; Membrane resistance ; Nerve stimulation ; Electrical field stimulation ; Acetylcholine ; Adrenaline
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Intracellular microelectrode recordings were made from superfused in vitro preparations of mouse lacrimal giand. The lacrimal acinar cell had a mean resting membrane potential of −44.1±0.5 mV and a mean input resistance of 3.5±0.15 MΩ. Electrical field stimulation (FS) had similar effects to ACh applied by microionophoresis, both evoking a biphasic membrane hyperpolarization (up to 15 mV) accompanied by a reduction in input resistance. The equilibrium potential values (EFS and EACh) for the responses to brief duration FS and ACh ionophoresis ranged between −45 and −75 mV and depended on the time at which measurements were made following the onset of stimulation. Superfusion of ACh or adrenaline also caused membrane hyperpolarization and increased membrane conductance. Estimations of EFS and EACh made during prolonged periods of FS and ACh superfusion yielded mean values of −53.9±1.9 mV and −53.4±1.5 mV respectively. FS evoked a response in all preparations tested with maximal effects seen at 40 Hz frequency. The mean latency of the FS-evoked hyperpolarization (40 Hz) was 270±21 ms and that for the ACh ionophoretic response was 400±65 ms. Low frequency FS (0.5–5 Hz) also induced membrane hyperpolarization and responses to single shock stimuli were occasionally observed. The FS-evoked hyperpolarization was abolished following the blockade of nerve conduction by superfusion of either Na-free or tetrodotoxin-containing media. Effects of FS were not seen in the presence of atropine. Neostigmine potentiated the FS- and ACh-evoked hyperpolarizations. Spontaneous miniature hyperpolarizations were unaffected by tetrodotoxin but abolished by atropine. It is concluded that FS excites a well developed cholinergic innervation of the mouse lacrimal gland resulting in ACh release and acinar cell hyperpolarization. ACh, which appears to be the only neurotransmitter released, mediates its effects by increasing plasma membrane permeability to mainly K ions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00670536
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  • 5
    Digitale Medien
    Digitale Medien
    Thyroid follicular cells: the resting membrane potential and the communication network (1981)
    Springer
    Pflügers Archiv 391 (1981), S. 119-124 
    Details
    ISSN: 1432-2013
    Schlagwort(e): Thyroid gland ; Follicular cell ; Membrane potential ; Membrane resistance ; Cell to cell coupling ; Specific membrane resistance ; Electrogenic pump
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Intracellular recordings of membrane potential, input resistance and time constant have been made in vitro from the follicular cells of the rat, rabbit and guinea-pig thyroid glands using glass microelectrodes. The passive permeability properties of these cells have been investigated by altering the concentration of one or more ions in the superfusing fluid. Investigations into the intercellular coupling characteristics of the thyroid gland were made by inserting two microelectrodes into neighbouring communicating cells. The mean transmembrane potentials were between −60 and −70 mV in all three species studied. The magnitude of the membrane potential in the rat was found to be dependent mainly upon the gradient for potassium (K+) across the membrane. Current-voltage relationships were investigated in all three species by injecting rectangular de- or hyperpolarizing current pulses through the recording microelectrode. Within a relatively wide range (−20 to −80 mV), there was an approximately linear relationship between injected current and change in membrane potential. The input resistance was about 11 MΩ in all three species, while the time constant (τ) varied from 5–35 ms. Readmitting K to K-deprived rat thyroids during intracellular microelectrode recording caused a transient hyperpolarization which was unaccomapanied by any change in input resistance. The transient hyperpolarization was abolished by ouabain. Addition of 10−3 M ouabain to the resting cell caused an immediate depolarization of approximately 2 mV. Electrical coupling between neighbouring cells could only be observed if the distance between the tips of the two exploring microelectrodes was less than 15 μm. The coupling coefficient (V 2/V 1) was close to 1. Assuming uniform current spread within one follicle and electrical isolation of individual follicles from each other the specific membrane resistance of the rat thyroid follicular cells was calculated to be 4.9 kΩcm2.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00657001
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  • 6
    Digitale Medien
    Digitale Medien
    Separate activation sites for cholecystokinin and bombesin on pancreatic acini (1979)
    Springer
    Pflügers Archiv 382 (1979), S. 263-267 
    Details
    ISSN: 1432-2013
    Schlagwort(e): Pancreatic acinar cells ; N2, O2′ dibutyryl guanosine 3′:5′-Monophosphate ; Cholecystokinin antagonist ; Bombesin ; Membrane potential
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The effects of dibutyryl cyclic guanosine 3′:5′ monophosphate (dbcGMP) on the electrical responses of in vitro mouse pancreatic acinar cells to caerulein, bombesin and acetylcholine, applied by microionophoresis, were investigated using intracellular microelectrode recordings. Exposure to dbcGMP (10−3 mol ·l−1) quickly abolished the depolarization response to caerulein ionophoresis, while the bombesin-nonapeptide and acetylcholine-induced depolarizations were retained. Exposing acinar cells to 2×10−4 mol·l−1 dbcGMP reduced their sensitivity such that a 10-fold increase in the applied caerulein ionophoresis current was required to restore the responses to the same magnitude as those obtained in a dbcGMP-free environment. The response to topical applications of pentagastrin and CCK-33 were also abolished by dbcGMP. The results provide direct evidence that functional ACh, bombesin and CCK receptors are all present within the same acinar cell unit. The dbcGMP-induced inhibition of responses evoked by CCK-like peptides is immediate, specific and easily reversible. DbcGMP acts as a competitive antagonist of the CCK receptor on pancreatic acinar cells.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00583711
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  • 7
    Digitale Medien
    Digitale Medien
    Effects of pyridine nucleotides on the gating of ATP-sensitive potassium channels in insulin-secreting cells (1988)
    Springer
    The journal of membrane biology 102 (1988), S. 205-216 
    Details
    ISSN: 1432-1424
    Schlagwort(e): K+ channel ; ATP ; NAD(P) ; NAD(P)H ; RINm5F cell
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary The single-channel current recording technique has been used to study the influences that the pyridine nucleotides NAD, NADH, NADP and NADPH have on the gating of ATP-sensitive K+ channels in an insulin-secreting cell line (RINm5F). The effects of the nucleotides were studied at the intracellular surface using either excised inside-out membrane patches or permeabilized cells. All four pyridine nucleotides were found to evoke similar effects. At low concentrations, 100 μm and less, each promoted channel opening whereas high concentrations, 500 μm and above, evoked channel closure. The degree of K+ channel activation by pyridine nucleotides (low conc.) was found to be similar to that evoked by the same concentrations of ADP or GTP, whereas the degree of K+ channel inhibition (high conc.) was less marked than that evoked by the same concentrations of ATP, and never resulted in refreshment of K+ channels following removal. The effects of NAD, NADH, NADP and NADPH seemed to interact with those of ATP and ADP. In the presence of 1mm ADP and 4mm ATP, 10 to 100 μm concentrations of the pyridine nucleotides could not evoke channel opening, whereas concentrations of 500 μm and above were found to evoke channel closure. In the presence of 2mm ATP and 0.5mm ADP, however, 10 to 100 μm concentrations of the pyridine nucleotides were able to activate K+ channels.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01925714
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  • 8
    Digitale Medien
    Digitale Medien
    Interaction of diazoxide, tolbutamide and ATP4− on nucleotide-dependent K+ channels in an insulin-secreting cell line (1987)
    Springer
    The journal of membrane biology 99 (1987), S. 215-224 
    Details
    ISSN: 1432-1424
    Schlagwort(e): K+ channel ; ATP ; diazoxide ; tolbutamide ; RINm5F cell
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary The single-channel current recording technique has been used to study the effects of diazoxide, tolbutamide and ATP, separately and combined, on the gating of nucleotide-regulated K+ channels in the insulin-secreting cell line RINm5F. The effects of diazoxide, tolbutamide and ATP4− were studied at the intracellular membrane surface, using, the open-cell membrane patch configuration. Alone diazoxide was found only inconsistently to evoke channel stimulation, 57% of all applications of the drug (72 times in 48 separate patches) having no effect at concentrations between 0.02 and 0.4mm. In the presence of ATP, however, diazoxide consistently evoked channel activation (seen 87 times in 49 patches, 95% of all applications). The interactions of diazoxide and ATP seemed competitive. Stimulation of channels by diazoxide in the presence of 1mm ATP was suppressed if the concentration of ATP was elevated to 2 or 5mm. In solutions in which Mg2+ had been chelated with EDTA, diazoxide failed to activate channels closed by 1mm ATP; however, this was not due to a direct effect on the channels caused by the absence of Mg2+, but could be explained by the enhanced ATP4− concentration after Mg2+ removal. When the total ATP concentration was lowered to give the same [ATP4−] in the absence of Mg2+ to that present in the control experiments, diazoxide was able to evoke full activation. Channel inhibition evoked by tolbutamide, 0.01 to 1.0mm, did not require the presence of either ATP or Mg2+. In the presence of ATP tolbutamide further reduced the number of channel openings. Diazoxide was able to compete with tolbutamide for control of channel activity, an effect that was augmented by the presence of ATP. In the presence of 0.1mm tolbutamide, diazoxide was unable to stimulate channel openings; however, if the dose of tolbutamide was lowered or ATP made available to the inside of the membrane, channel stimulation occurred.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01995702
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  • 9
    Digitale Medien
    Digitale Medien
    Stimulant-evoked depolarization and increase in [Ca2+] i in insulin-secreting cells is dependent on external Na+ (1990)
    Springer
    The journal of membrane biology 113 (1990), S. 131-138 
    Details
    ISSN: 1432-1424
    Schlagwort(e): patch clamp ; [Ca2+] i ; Na+ dependency ; RINm5F cell ; fura-2 ; whole cell
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary The patch-clamp technique and measurements of single cell [Ca2+] i have been used to investigate the importance of extracellular Na+ for carbohydrate-induced stimulation of RINm5F insulin-secreting cells. Using patch-clamp whole-cell (current-clamp) recordings the average cellular transmembrane potential was estimated to be −60±1 mV (n=83) and the average basal [Ca2+] i 102±6nm (n=37). When challenged with either glucose (2.5–10mm) ord-glyceraldehyde (10mm) the cells depolarized, which led to the initiation of Ca2+ spike potentials and a sharp rise in [Ca2+] i . Similar effects were also observed with the sulphonylurea compound tolbutamide (0.01–0.1mm). Both the generation of the spike potentials and the increase in [Ca2+] i were abolished when Ca2+ was removed from the bathing media. When all external Na+ was replaced with N-methyl-d-glucamine, in the continued presence of either glucose,d-glyceraldehyde or tolbutamide, a membrane repolarization resulted, which terminated Ca2+ spike potentials and attenuated the rise in [Ca2+] i . Tetrodotoxin (TTX) (1–2 μm) was also found to both repolarize the membrane and abolish secretagogue-induced rises in [Ca2+] i .
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01872887
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  • 10
    Digitale Medien
    Digitale Medien
    Comparative study of the effects of cromakalim (BRL 34915) and diazoxide on membrane potential, [Ca2+] i and ATP-sensitive potassium currents in insulin-secreting cells (1990)
    Springer
    The journal of membrane biology 114 (1990), S. 53-60 
    Details
    ISSN: 1432-1424
    Schlagwort(e): patch-clamp ; fura-2 ; KATP channels ; [Ca2+] i ; insulin-secreting cell ; RINm5F cell ; diazoxide ; cromakalim (BRL 34915) ; tolbutamide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary Patch-clamp and single cell [Ca2+] i measurements have been used to investigate the effects of the potassium channel modulators cromakalim, diazoxide and tolbutamide on the insulin-secreting cell line RINm5F. In intact cells, with an average cellular transmembrane potential of −62±2 mV (n=42) and an average basal [Ca2+] i of 102±6nm (n=37), glucose (2.5–10mm): (i) depolarized the membrane, through a decrease in the outward KATP current, (ii) evoked Ca2+ spike potentials, and (iii) caused a sharp rise in [Ca2+] i . In the continued presence of glucose both cromakalim (100–200 μm) and diazoxide (100 μm) repolarized the membrane, terminated Ca2+ spike potentials and attenuated the secretagogue-induced rise in [Ca2+] i . In whole cells (voltage-clamp records) and excised outside-out membrane patches, both cromakalim and diazoxide enhanced the current by opening ATP-sensitive K+ channels. Diazoxide was consistently found to be more potent than cromakalim. Tolbutamide, a specific inhibitor of ATP-sensitive K+ channels, reversed the effects of cromakalim on membrane potential and KATP currents.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01869384
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