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4 results on '"I. Findlay"'

1. Quinine inhibits Ca2+ -independent K+ channels whereas tetraethylammonium inhibits Ca2+ -activated K+ channels in insulin-secreting cells

Author

M. J. Dunne, I. Findlay, Ole H. Petersen, Susanne Ullrich, and Claes B. Wollheim

Subjects
medicine.medical_specialty, RINm5F cell, K+ channel, Potassium, Biophysics, chemistry.chemical_element, Calcium, Biochemistry, Ion Channels, Cell Line, chemistry.chemical_compound, Structural Biology, Internal medicine, Genetics, medicine, Animals, Patch clamp, Molecular Biology, Membrane potential, Tetraethylammonium, Quinine, Chemistry, Inward-rectifier potassium ion channel, Cell Membrane, Electric Conductivity, Cell Biology, Tetraethylammonium Compounds, Hyperpolarization (biology), Adenoma, Islet Cell, Pancreatic Neoplasms, Membrane, Endocrinology, Insulinoma
Abstract

The effects of quinine and tetraethylammonium (TEA) on single-channel K + currents recorded from excised membrane patches of the insulin-secreting cell line RINm5F were investigated. When 100 μM quinine was applied to the external membrane surface K + current flow through inward rectifier channels was abolished, while a separate voltage-activated high-conductance K + channel was not significantly affected. On the other hand, 2 mM TEA abolished current flow through voltage-activated high-conductance K + channels without influencing the inward rectifier K + channel. Quinine is therefore not a specific inhibitor of Ca 2+ -activated K + channels, but instead a good blocker of the Ca 2+ -independent K + inward rectifier channel whereas TEA specifically inhibits the high-conductance voltage-activated K + channel which is also Ca 2+ -activated.

Published
1985
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2. Voltage-activated Ca2+ currents in insulin-secreting cells

Author

M. J. Dunne and I. Findlay

Subjects
Nifedipine, RINm5F cell, Biophysics, Biochemistry, Ion Channels, Cell Line, Membrane Potentials, Whole-cell patch clamp, Structural Biology, Insulin Secretion, Genetics, Extracellular, Animals, Insulin, Patch clamp, Molecular Biology, Spike potential, Egtazic Acid, Evoked Potentials, Membrane potential, Chemistry, Electric Conductivity, Depolarization, Cell Biology, Cobalt, Hyperpolarization (biology), Membrane, Verapamil, Secretagogue, Calcium, Ca2+ current
Abstract

Membrane voltage and voltage-clamped membrane currents have been investigated with the whole-cell patch clamp method in the insulin-secreting cell line RINm5F. The mean resting membrane potential of RINm5F cells was found to be −52 mV. Overshooting spike potentials could be evoked by membrane depolarisation in the absence of a secretagogue. Inward membrane currents evoked by depolarising voltage steps were dependent upon extracellular Ca2+ and blocked by Co2+, nifedipine and verapamil. Outward membrane currents which were evoked by depolarising voltage steps to positive membrane potentials were reduced when Ca2+ entry was prevented. It is concluded that the voltage-activated Ca2+ currents underlie the voltage-activated spike potentials recorded from insulin-secreting cells.

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3. Molecular cloning, functional expression and localization of an inward rectifier potassium channel in the mouse brain.

Author

Morishige K, Takahashi N, Findlay I, Koyama H, Zanelli JS, Peterson C, Jenkins NA, Copeland NG, Mori N, and Kurachi Y

Subjects
Animals, Barium pharmacology, Brain cytology, Cesium pharmacology, Chromosome Mapping, Cloning, Molecular, Female, Gene Library, In Situ Hybridization, Membrane Potentials drug effects, Mice, Oocytes drug effects, Oocytes physiology, Potassium Channels genetics, RNA, Messenger analysis, Restriction Mapping, Xenopus, Brain metabolism, Potassium Channels biosynthesis, Potassium Channels physiology, RNA, Messenger biosynthesis
Abstract

We have cloned an inward-rectifier potassium channel from a mouse brain cDNA library, studied its distribution in the brain by in situ hybridization and determined the chromosomal localization of the gene. A mouse brain cDNA library was screened using a fragment of the mouse macrophage IRK1 cDNA as a probe. Two duplicate clones of approximately 5.5 kb were obtained. Xenopus ococytes injected with cRNA derived from the clone expressed a potassium channel with inwardly rectifying channel characteristics. The amino acid sequence of the clone was identical to that of IRK1 recently cloned from a mouse macrophage cell line. In situ hybridization study showed the mouse brain IRK1 to be generally distributed throughout the brain, but in particular subsets of neurons at high levels. The gene was placed in the distal region of mouse chromosome 11, which contains several uncloned neurological mutations. These results provide the first demonstration of the cloning and distribution of an inward rectifier potassium channel from the nervous system.

Published
1993
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4. ATP-sensitive K channels in heart muscle. Spare channels.

Author

Findlay I and Faivre JF

Subjects
Animals, Membrane Potentials, Rats, Adenosine Triphosphate metabolism, Muscle, Smooth metabolism, Potassium Channels metabolism
Abstract

We show that ATP-sensitive K+ channels of excised inside-out membrane patches of rat ventricular myocytes show considerable variation in their sensitivity to ATP. In 102 different membrane patches IC50 values ranged from 9 to 580 microM ATP and Hill coefficients from 1% to 6.41% of patches showed openings of ATP-sensitive K+ channels in the presence of 1 mM ATP. These results considerably widen the range of internal ATP concentrations over which one might expect activation of the ATP-sensitive K+ current in cardiac myocytes.

Published
1991
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