Effects of voltage-gated sodium channel inhibition on islet [Ca²⁺]<i>_i</i> and hormone secretion.

<p>Gray and black traces represent α- and β-cells, respectively. A, representative intracellular calcium responses to tetrodotoxin (TTX) in an intact mouse islet perifused at 1 mM glucose. Increasing concentrations of TTX were perifused at times indicated by the arrows. TTX stimulates calcium activity in α-cells while having no noticeable effects on β-cells. Fluo-4 intensity is expressed in arbitrary units. The figure is representative of 18 α-cells analyzed from 6 islets harvested from 3 mice. B, effects of TTX on glucagon and insulin secretion from intact perifused islets. Isolated islets were exposed to 1 mM glucose for 30 minutes (from −30 to 0 min). Glucagon and insulin responses were measured for 9 minutes at 1 mM glucose (G1), and then TTX was perifused. Experiment was repeated 6 times, 900 islets from 12 mice were used. Error bars represent the standard error of the mean.