Interaction of diazoxide and cromakalim with ATP-regulated K+ channels in rodent and clonal insulin-secreting cells

Jonathan Jaggar, E. A. Harding, B. J. Ayton, M. J. Dunne

Research output: Contribution to journalArticle

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Abstract

The hyperglycaemia-inducing sulphonamide diazoxide has been previously shown to mediate its effects upon insulin secretion by opening K+ channels and hyperpolarizing the β-cell membrane. The target site has been characterized as the ATP-regulated K+ (K+ (ATP)) channel protein. In the present study, a detailed investigation of interactions of diazoxide and another K+ channel opener, cromakalin, with K+ (ATP) channels has been performed in individual insulin-secreting cells using patch-clamp techniques. In agreement with previous studies, diazoxide and cromakalin were found to be effective only when ATP was present upon the inside face of the plasma membrane. The ability of both diazoxide and cromakalim to open channels was, however, found to diminish with time following isolation of inside-out patches. Within seconds of forming the recording configuration, the actions of both compounds were potent, and were found to decline steadily as the number of operational channels decreased ('run-down'). In open cells, where the plasma membrane remains partially intact, the rate of run-down was significantly reduced, and effects of channel openers were recorded up to 80 min following cell permeabilization. We also demonstrated that in the absence of ATP, but in the presence of ADP, both diazoxide and cromakalin were able to open K+ (ATP) channels. Interestingly, once the effects of diazoxide and cromakalim on K+ (ATP) channels in the presence of ATP were lost, both compounds opened channels in the presence of ADP. One implication of these data is that the actions of diazoxide and cromakalim involve regulatory proteins associated with the ion channel; this molecule is able to bind ATP, ADP and possibly other cytosolic nucleotides.

Original languageEnglish (US)
Pages (from-to)59-70
Number of pages12
JournalJournal of Molecular Endocrinology
Volume10
Issue number1
DOIs
StatePublished - Jan 1 1993
Externally publishedYes

Fingerprint

Cromakalim
Diazoxide
Insulin-Secreting Cells
Rodentia
Adenosine Triphosphate
Cell Membrane
Adenosine Diphosphate
Sulfonamides
Patch-Clamp Techniques
Ion Channels
Hyperglycemia
Proteins
Nucleotides
Insulin

All Science Journal Classification (ASJC) codes

  • Molecular Biology
  • Endocrinology

Cite this

Interaction of diazoxide and cromakalim with ATP-regulated K+ channels in rodent and clonal insulin-secreting cells. / Jaggar, Jonathan; Harding, E. A.; Ayton, B. J.; Dunne, M. J.

In: Journal of Molecular Endocrinology, Vol. 10, No. 1, 01.01.1993, p. 59-70.

Research output: Contribution to journalArticle

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