Thiopental inhibits K+ permeability of rat and mouse pancreatic β-cells

doi:10.1016/0014-2999(86)90090-7

European Journal of Pharmacology

Volume 125, Issue 1, 5 June 1986, Pages 119-125

https://doi.org/10.1016/0014-2999(86)90090-7 Get rights and content

Abstract

The effects of thiopental on the insulin release and ⁸⁶Rb efflux from isolated rat islets and on parameters of the electrical activity of single β-cells of mice were studied. Thiopental 0.2 and 1.0 mM increased by 16.6 and 33.3%, respectively, the insulin release induced by 6.0 mM glucose. Thiopental reduced the ⁸⁶Rb efflux rate in both 0 and 6.0 mM glucose, but had only a slight effect in 16.7 mM glucose. Menadione (20 μM) did not block the inhibitory effect of thiopental on ⁸⁶Rb efflux. Thiopental induced a reversible membrane depolarization in a dose-dependent manner (0.2-1.0 mM). It also induced electrical activity at a subthreshold glucose concentration and continuous spiking in presence of 11.1 mM glucose. In the presence of 2,4-dinitrophenol (20 μM) this continuous spiking was changed to an oscillatory activity similar to that induced by 11.1 mM glucose. Thiopental (0.5 mM) induced an increase in input resistance of 12.7, 17.9 and 16.0% in 0, 5.6 and 11.1 mM glucose, respectively . The thiopental-induced changes in insulin secretion, ⁸⁶Rb efflux and electrical parameters indicate that K⁺ permeability was affected in both rat and mouse β-cells. Our results suggest that thiopental is a direct inhibitor of the glucose-sensitive K⁺ permeability in the β-cell.

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Highly purified Tityustoxin V (TsTX-V), an a-toxin isolated from the venom of the Brazilian scorpion Tityus serrulatus, was obtained by ion exchange chromatography on carboxymethylcellulose-52. It was shown to be homogeneous by reverse phase high performance liquid chromatography, N-terminal sequencing (first 39 residues) of the reduced and alkylated protein and by polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate and tricine. Following enzymatic digestion, the complete amino acid sequence (64 residues) was determined. The sequence showed higher homology with the toxins from the venoms of the North African than with those of the North and South American scorpions. Using the rate of ⁸⁶Rb⁺ release from depolarized rat pancreatic /gb-cells as a measure of K⁺ permeability changes, TsTX-V (5.6 μg/ml) was found to increase by 2.0–2.4-fold the rate of marker outflow in the presence of 8.3 mM glucose. This effect was persistent and slowly reversible, showing similarity to that induced by 100 μM veratridine, an agent that increases the open period of Na⁺ channels, delaying their inactivation. It is suggested that, by extending the depolarized period, TsTX-V indirectly affects β-cell voltage-dependent K⁺ channels, thus increasing K⁺ permeability.
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Thiopental inhibits K+ permeability of rat and mouse pancreatic β-cells

Abstract

Cell Calsium

FEBS Lett.

FEBS Lett.

Brain Res.

Biochem. Pharmacol.

A barbiturate-induced potassium permeability increase in the myelinated nerve membrane

Acta Physiol. Scand.

Glucose induces closure of single potassium channels in isolated rat pancreatic β-cells

nature

Control mechanisms for glucose-induced changes in the membrane potential of mouse pancreatic β-cell

Ciênc. Biol. (Portugal)

Electrophysiological measurement of an oscillating potassium permeability during the glucose-stimulated burst activity in mouse pancreatic β-cell

Biomed. Res.

Cyclic changes in potential and resistance of the β-cell membrane induced by glucose in islets of Langerhans from mouse

J. Physiol.

Barbiturates block sodium and potassium conductance increases in voltage clamped lobster axons

J. Gen. Physiol.

Effect of menadione on bioelectrical activity in the pancreatic B-cell

IRCS Med. Sci.

Valinomycin inhibition of the electrical activity of mouse pancreatic β-cells

Braz. J. Med. Biol. Res.

Thiopental induces K+-permeability alterations in beta cells: effects on membrane potential and input resistance

Braz. J. Med. Biol. Res.

Intracellular ATP directly blocks K+ channels in pancreatic β-cells

Nature

Decreasing pHi inhibits Ca++ activated K+ channels in pancreatic β-cells

Nature

Thiopental inhibits K⁺ permeability of rat and mouse pancreatic β-cells

Thiopental induces K⁺-permeability alterations in beta cells: effects on membrane potential and input resistance

Intracellular ATP directly blocks K⁺ channels in pancreatic β-cells

Decreasing pH_i inhibits Ca⁺⁺ activated K⁺ channels in pancreatic β-cells