Na+ channels in pancreatic islet cells.

Experiments are reviewed which show that Na+ channels which are pharmacologically identical with those found in spiking neurones are present in the outer membrane of pancreatic beta-cells. In both nerve and beta-cells the neurotoxins veratridine, scorpion toxin, and tetrodotoxin bind to three distinctly separate sites on the sodium channel, the affinity of each of these sites for its respective toxin being similar in the two tissues. The binding sites for veratridine and scorpion toxin exhibit reciprocal, positive, heterotropic cooperativity. The role of these Na+ channels in the physiological regulation of insulin release is discussed.