Sodium channels contribute to action potential generation in canine and human pancreatic islet B cells.
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 a KI = 3.2 nM 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.
Pressel
D M
DM
Department of Medicine (Jewish Hospital), Washington University, St. Louis, Missouri 63110.
Misler
S
S
D000200:Action Potentials; D000818:Animals; D004285:Dogs; D004553:Electric Conductivity; D005947:Glucose / Q000494:pharmacology; D006801:Humans; D007515:Islets of Langerhans / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D015222:Sodium Channels / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology
D015222:Sodium Channels; D013779:Tetrodotoxin; D012964:Sodium; D005947:Glucose