Properties of diazoxide and cromakalim‐induced activation of potassium channels in cultured rat and RINm5F insulin‐secreting cells; effects of GTP

EA Harding, Jonathan Jaggar, BJ Ayton, MJ Dunne

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Experiments have been carried out to examine the effects of GTP on the opening of K+ channels in insulin‐secreting cells by diazoxide (0.2 mM) and cromakalim (0.5 mM). Using rat pancreatic beta‐cells and RINm5F insulinoma cells, patch‐clamp recordings of unitary ATP‐sensitive potassium (K+ATP) channel currents were made in either the open cell or outside‐out patch recording configurations. Adding diazoxide or cromakalim to either the inside or the outside face of the membrane was found regularly to cause the activation of K+ATP channels in the presence of 0.5 mM ATP. We now demonstrate that in the absence of ATP but in the presence of GTP (0.5–1 mM), both diazoxide and cromakalim activate channels. Effects are rapid in onset, sustained and readily reversible. Both the diazoxide‐ and cromakalim‐induced activation of K+ATP channels were mediated by increases in channel open‐state probability, and were not associated with any significant change in either channel amplitude or by an increase in the number of channels in the patch. The actions of both diazoxide and cromakalim were not affected by overnight pretreatment of cells with pertussis toxin, suggesting that PTX‐sensitive GTP‐binding proteins are not involved in mediating the actions of either compound. These data indicate that diazoxide and cromakalim open K+ATP channels in a manner not solely dependent upon intracellular ATP, but by mechanisms involving other cytosolic nucleotides, including GTP.

Original languageEnglish (US)
Pages (from-to)25-34
Number of pages10
JournalExperimental Physiology
Volume78
Issue number1
DOIs
StatePublished - Jan 1 1993

Fingerprint

Diazoxide
Potassium Channels
Guanosine Triphosphate
Cromakalim
Adenosine Triphosphate
Insulinoma
Pertussis Toxin
Potassium
Nucleotides
Membranes

All Science Journal Classification (ASJC) codes

  • Physiology

Cite this

Properties of diazoxide and cromakalim‐induced activation of potassium channels in cultured rat and RINm5F insulin‐secreting cells; effects of GTP. / Harding, EA; Jaggar, Jonathan; Ayton, BJ; Dunne, MJ.

In: Experimental Physiology, Vol. 78, No. 1, 01.01.1993, p. 25-34.

Research output: Contribution to journalArticle

@article{34db2be9416942cd82736f6efd38c112,
title = "Properties of diazoxide and cromakalim‐induced activation of potassium channels in cultured rat and RINm5F insulin‐secreting cells; effects of GTP",
abstract = "Experiments have been carried out to examine the effects of GTP on the opening of K+ channels in insulin‐secreting cells by diazoxide (0.2 mM) and cromakalim (0.5 mM). Using rat pancreatic beta‐cells and RINm5F insulinoma cells, patch‐clamp recordings of unitary ATP‐sensitive potassium (K+ATP) channel currents were made in either the open cell or outside‐out patch recording configurations. Adding diazoxide or cromakalim to either the inside or the outside face of the membrane was found regularly to cause the activation of K+ATP channels in the presence of 0.5 mM ATP. We now demonstrate that in the absence of ATP but in the presence of GTP (0.5–1 mM), both diazoxide and cromakalim activate channels. Effects are rapid in onset, sustained and readily reversible. Both the diazoxide‐ and cromakalim‐induced activation of K+ATP channels were mediated by increases in channel open‐state probability, and were not associated with any significant change in either channel amplitude or by an increase in the number of channels in the patch. The actions of both diazoxide and cromakalim were not affected by overnight pretreatment of cells with pertussis toxin, suggesting that PTX‐sensitive GTP‐binding proteins are not involved in mediating the actions of either compound. These data indicate that diazoxide and cromakalim open K+ATP channels in a manner not solely dependent upon intracellular ATP, but by mechanisms involving other cytosolic nucleotides, including GTP.",
author = "EA Harding and Jonathan Jaggar and BJ Ayton and MJ Dunne",
year = "1993",
month = "1",
day = "1",
doi = "10.1113/expphysiol.1993.sp003668",
language = "English (US)",
volume = "78",
pages = "25--34",
journal = "Experimental Physiology",
issn = "0958-0670",
publisher = "Wiley-Blackwell",
number = "1",

}

TY - JOUR

T1 - Properties of diazoxide and cromakalim‐induced activation of potassium channels in cultured rat and RINm5F insulin‐secreting cells; effects of GTP

AU - Harding, EA

AU - Jaggar, Jonathan

AU - Ayton, BJ

AU - Dunne, MJ

PY - 1993/1/1

Y1 - 1993/1/1

N2 - Experiments have been carried out to examine the effects of GTP on the opening of K+ channels in insulin‐secreting cells by diazoxide (0.2 mM) and cromakalim (0.5 mM). Using rat pancreatic beta‐cells and RINm5F insulinoma cells, patch‐clamp recordings of unitary ATP‐sensitive potassium (K+ATP) channel currents were made in either the open cell or outside‐out patch recording configurations. Adding diazoxide or cromakalim to either the inside or the outside face of the membrane was found regularly to cause the activation of K+ATP channels in the presence of 0.5 mM ATP. We now demonstrate that in the absence of ATP but in the presence of GTP (0.5–1 mM), both diazoxide and cromakalim activate channels. Effects are rapid in onset, sustained and readily reversible. Both the diazoxide‐ and cromakalim‐induced activation of K+ATP channels were mediated by increases in channel open‐state probability, and were not associated with any significant change in either channel amplitude or by an increase in the number of channels in the patch. The actions of both diazoxide and cromakalim were not affected by overnight pretreatment of cells with pertussis toxin, suggesting that PTX‐sensitive GTP‐binding proteins are not involved in mediating the actions of either compound. These data indicate that diazoxide and cromakalim open K+ATP channels in a manner not solely dependent upon intracellular ATP, but by mechanisms involving other cytosolic nucleotides, including GTP.

AB - Experiments have been carried out to examine the effects of GTP on the opening of K+ channels in insulin‐secreting cells by diazoxide (0.2 mM) and cromakalim (0.5 mM). Using rat pancreatic beta‐cells and RINm5F insulinoma cells, patch‐clamp recordings of unitary ATP‐sensitive potassium (K+ATP) channel currents were made in either the open cell or outside‐out patch recording configurations. Adding diazoxide or cromakalim to either the inside or the outside face of the membrane was found regularly to cause the activation of K+ATP channels in the presence of 0.5 mM ATP. We now demonstrate that in the absence of ATP but in the presence of GTP (0.5–1 mM), both diazoxide and cromakalim activate channels. Effects are rapid in onset, sustained and readily reversible. Both the diazoxide‐ and cromakalim‐induced activation of K+ATP channels were mediated by increases in channel open‐state probability, and were not associated with any significant change in either channel amplitude or by an increase in the number of channels in the patch. The actions of both diazoxide and cromakalim were not affected by overnight pretreatment of cells with pertussis toxin, suggesting that PTX‐sensitive GTP‐binding proteins are not involved in mediating the actions of either compound. These data indicate that diazoxide and cromakalim open K+ATP channels in a manner not solely dependent upon intracellular ATP, but by mechanisms involving other cytosolic nucleotides, including GTP.

UR - http://www.scopus.com/inward/record.url?scp=0027473793&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0027473793&partnerID=8YFLogxK

U2 - 10.1113/expphysiol.1993.sp003668

DO - 10.1113/expphysiol.1993.sp003668

M3 - Article

VL - 78

SP - 25

EP - 34

JO - Experimental Physiology

JF - Experimental Physiology

SN - 0958-0670

IS - 1

ER -