Electrophysiology of the pancreas.

Petersen, O. H.; Findlay, Ian

doi:10.1152/physrev.1987.67.3.1054

Cited by 268 publications

(152 citation statements)

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“…The resulting massive influx of Ca 2C , mainly through the Ca 2C voltage-dependent L-type channels, increases the cytosolic Ca 2C concentration and stimulates insulin secretion (Petersen and Findlay, 1987;Grodsky, 1989).…”

Section: Discussionmentioning

confidence: 99%

Characterization of the insulinotropic action of a phospholipase A2 isolated from Crotalus durissus collilineatus rattlesnake venom on rat pancreatic islets

Nogueira

Ferreira

Toyama

et al. 2005

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The ability of PLA 2 and crotapotin, isolated from Crotalus durissus collilineatus rattlesnake venom, to stimulate insulin secretion from isolated rat islets was examined. PLA 2 and crotapotin stimulated insulin secretion at 2.8 mmol/L glucose, whereas at a high glucose concentrations (16.7 mmol/L) only PLA 2 stimulated secretion. Nifedipine (10 mmol/L) did not alter the ability of PLA 2 to increase insulin secretion stimulated by a depolarizing concentration of K C (30 mmol/L). PLA 2 did not affect 14 CO 2 production but significantly increased the efflux of arachidonic acid from isolated islets. These results indicate that PLA 2 -stimulated secretion is not dependent on an additional influx of Ca 2C through L-type Ca 2C -channels but rather is associated with arachidonic acid formation in pancreatic islets. q

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Section: Discussionmentioning

confidence: 99%

Characterization of the insulinotropic action of a phospholipase A2 isolated from Crotalus durissus collilineatus rattlesnake venom on rat pancreatic islets

Nogueira

Ferreira

Toyama

et al. 2005

Toxicon

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“…All single channel recordings presented in this paper were derived exclusively from currents passing through K ATP channels in outside-out patches and with the membrane potential clamped at 0 mV. The Ca 2ϩ -activated nonselective cation channels and the Ca 2ϩ -activated K ϩ channels were eliminated by keeping the [Ca 2ϩ ] i low, Ͻ10 Ϫ9 M, and by applying 5 mM tetraethylammonium extracellularly (7). Because the number of operational K ATP channels per membrane patch is often unknown, NP o was introduced to estimate the channel activity (see "Experimental Procedures").…”

Section: Effects Of Ne On the Membrane Potential Of Ins 832/13 Cells-mentioning

confidence: 99%

Both Gi and Go Heterotrimeric G Proteins Are Required to Exert the Full Effect of Norepinephrine on the β-Cell KATP Channel

Zhao

Fang

Straub

et al. 2008

Journal of Biological Chemistry

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The effects of norepinephrine (NE), an inhibitor of insulin secretion, were examined on membrane potential and the ATPsensitive K ؉ channel (K ATP ) in INS 832/13 cells. Membrane potential was monitored under the whole cell current clamp mode. NE hyperpolarized the cell membrane, an effect that was abolished by tolbutamide. The effect of NE on K ATP channels was investigated in parallel using outside-out single channel recording. This revealed that NE enhanced the open activities of the K ATP channels ϳ2-fold without changing the single channel conductance, demonstrating that NE-induced hyperpolarization was mediated by activation of the K ATP channels. The NE effect was abolished in cells preincubated with pertussis toxin, indicating coupling to heterotrimeric G i /G o proteins. To identify the G proteins involved, antisera raised against ␣ and ␤ subunits (anti-G␣ common , anti-G␤, anti-G␣ i1/2/3 , and anti-G␣ o ) were used. Anti-G␣ common totally blocked the effects of NE on membrane potential and K ATP channels. Individually, anti-G␣ i1/2/3 and anti-G␣ o only partially inhibited the action of NE on K ATP channels. However, the combination of both completely eliminated the action. Antibodies against G ␤ had no effects. To confirm these results and to further identify the G protein subunits involved, the blocking effects of peptides containing the sequence of 11 amino acids at the C termini of the ␣ subunits were used. The data obtained were similar to those derived from the antibody work with the additional information that G␣ i3 and G␣ o1 were not involved. In conclusion, both G i and G o proteins are required for the full effect of norepinephrine to activate the K ATP channel.Insulin secretion is inhibited by ␣ 2 -adrenergic receptor activation (1, 2). The ␣ 2 -adrenergic receptors at the plasma membrane are linked to pertussis toxin (PTX) 2 -sensitive G i and G o proteins. Upon interacting with the ␣ 2 -adrenergic receptors, catecholamines (i.e. epinephrine and norepinephrine (NE)), two important physiological inhibitors of insulin secretion, activate G i and/or G o proteins and inhibit the exocytosis of insulin-containing granules (2). Four mechanisms have been suggested to account for their inhibitory effect: 1) activation of ATP-sensitive K ϩ channels (K ATP ) and repolarization of the ␤-cells; 2) inhibition of L-type Ca 2ϩ channels; 3) decreased activity of adenylyl cyclase; and 4) inhibition of exocytosis at a "distal" site in stimulus-secretion coupling, which is beyond the elevation of intracellular Ca 2ϩ and beyond the potentiating actions of cAMP and diacyglycerol (2). Although it is generally accepted that the "distal" inhibitory effect is the most dominant, the relative contribution of each of these four mechanisms to the overall inhibition of insulin release is not clear.Considering the effects of catecholamines on the membrane potential in the insulin-secreting cells, it is clear that catecholamines can repolarize the cell membrane in a PTX-sensitive manner. However, the explanations for this p...

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“…These Ca 2ϩ channels are opened by membrane depolarization, which is mediated by closure of ATP/ADP-sensitive K ϩ channels (1,2). It is well known that insulin secretion in response to glucose and other nutrients (amino acids) is markedly potentiated by the actions of several neurotransmitters and hormones (3).…”

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confidence: 99%