Summary
Pancreatic islet B cells depolarize and display trains of action potentials in response to stimulatory concentrations of glucose. Based on data from rodent islets these action potentials are considered to be predominantly Ca2+ dependent. Here we describe Na+-dependent action potentials and Na+ currents recorded from canine and human pancreatic islet B cells. Current-clamp recording using the nystatin “perforated-patch” technique demonstrates that B cells from both species display tetrodotoxin-sensitive Na+ action potentials in response to modest glucose-induced depolarization. In companion “whole-cell” voltage-clamp experiments on canine B cells, the underlying Na+ current displays steep voltage-dependent activation and inactivation over the range of −50 to −40 mV. The Na+ current is sensitive to tetrodotoxin block with aK 1=3.2nm and has a reversal potential which changes with [Na+] o as predicted by the Nernst equation. These results suggest that a voltage-dependent Na+ current may contribute significantly to action potential generation in some species outside the rodent family.
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Pressel, D.M., Misler, S. Sodium channels contribute to action potential generation in canine and human pancreatic islet B cells. J. Membrain Biol. 116, 273–280 (1990). https://doi.org/10.1007/BF01868466
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DOI: https://doi.org/10.1007/BF01868466