Polymyxin B has multiple blocking actions on the ATP-sensitive potassium channel in insulin-secreting cells

Harding, E. A. and Jaggar, J. H. and Squires, Paul E. and Dunne, M. J. (1994) Polymyxin B has multiple blocking actions on the ATP-sensitive potassium channel in insulin-secreting cells. Pflugers Archiv European Journal of Physiology, 426 (1-2). pp. 31-39. ISSN 0031-6768

Full content URL: http://link.springer.com/article/10.1007%2FBF00374...

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Item Type:Article
Item Status:Live Archive

Abstract

The action of polymyxin B (0.1 μM) on ATP-sensitive K+ (K+ ATP) channels in RINm5F insulin-secreting cells was investigated by patch-clamp techniques. Using inside-out patches, open-cells and outside-out patches, polymyxin B was found to block K+ ATP channels by, on average, approximately 90-95 of the initial control level of channel activity. The effects were rapid in onset, sustained and readily reversible. Similar effects were found in patches excised from cells pretreated overnight with 1 μM of the phorbol ester phorbol myristate acetate (PMA). External block of channels was associated with a marked decrease in single-channel current amplitude, whereas these effects were not seen when polymyxin B was added to the inside face of the membrane. In patches bathed with internally applied ATP (0.5 mM) and ADP (0.5 mM), polymyxin B inhibited channels but its actions were not reversible upon removal of the compound. However, when the same protocol was undertaken upon cells pre-treated with PMA, the effects of polymyxin B were readily reversed. Our data suggests that polymyxin B is a novel modulator of K+ ATP channels, exhibiting multiple blocking actions that may possibly involve a direct effect upon the channel and indirect effects mediated through the inhibition of endogenous protein kinase(s). © 1994 Springer-Verlag.

Keywords:adenosine diphosphate, adenosine triphosphate, insulin, phorbol ester, polymyxin B, potassium channel, animal cell, article, controlled study, nonhuman, pancreas cell, priority journal, rat, Adenosine Diphosphate, Animal, Cell Line, Islets of Langerhans, Potassium Channel Blockers, Potassium Channels, Rats, Support, Non-U.S. Gov't
Subjects:C Biological Sciences > C130 Cell Biology
Divisions:College of Science > School of Life Sciences
ID Code:14517
Deposited On:16 Jul 2014 14:54

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