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Submitted on April 4, 2006
Accepted on July 11, 2006
cells: a comparison of islet cell electrical activity in mouse and rat
Departments of Physiologyand Medicine, University of Toronto, Ontario, Canada; and the Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia
* To whom correspondence should be addressed. E-mail: j.manningfox{at}utoronto.ca.
In contrast to mouse, rat islet 
cell membrane potential is reported not to oscillate in response to elevated glucose despite demonstrated oscillations in calcium and insulin secretion. We aim to clarify the electrical activity of rat islet cells and characterize and compare the electrical activity of both 
and cells in rat and mouse islets.
We recorded electrical activity from and cells within intact islets from both mouse and rat using the perforated whole-cell patch clamp technique. Fifty-six percent of both mouse and rat cells exhibited an oscillatory response to 11.1 mmol/liter glucose. Responses to both 11.1 mmol/liter and 2.8 mmol/liter glucose were identical in the two species. Rat cells exhibited incremental depolarization in a glucose concentration-dependent manner. We also demonstrated electrical activity in human islets recorded under the same conditions. In both mouse and rat cells 11 mmol/liter glucose caused hyperpolarization of the membrane potential whereas 2.8 mmol/liter glucose produced action potential firing. No species differences were observed in the response of cells to glucose. This paper is the first to demonstrate and characterize oscillatory membrane potential fluctuations in the presence of elevated glucose in rat islet cells in comparison to mouse. The findings promote the use of rat islets in future electrophysiological studies enabling consistency between electrophysiological and insulin secretion studies. An inverse response of cell membrane potential to glucose furthers our understanding of the mechanisms underlying glucose sensitive glucagon secretion.
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