Voltage-dependent Na+ and Ca2+ currents in human pancreatic islet ?-cells: evidence for roles in the generation of action potentials and insulin secretion

TTX reduces insulin secretion in human β-cells, with its effect particularly strong at 6 mM glucose and weaker at 10-20 mM glucose.

“Furthermore, TTX reduces insulin secretion: its effect is particularly strong at glucose concentrations just above the threshold for GIIS (6 mM) but is weaker at higher (10-20 mM) concentrations (52, 90) (see Figure 13C-D).”

Human β-cells (unlike mouse β-cells) are equipped with T-type Ca2+-channels that activate at membrane potentials as negative as -60 mV.

“Second, human β-cells (unlike mouse β-cells) are equipped with T-type Ca2+-channels that activate at membrane potentials as negative as -60 mV (52, 90).”

Na+ channels play a particularly important role at glucose concentrations just above the threshold for triggering electrical activity in human β-cells.

“Na+ channels play a particularly important role at glucose concentrations just above the threshold for triggering electrical activity (52, 90).”

The membrane potential during interspike intervals in human β-cells may be as negative as -60 mV at 6 mM glucose, but is between -50 and -40 mV at 10 mM glucose or above.

“This may be seen from the fact that the membrane potential during the interspike intervals may be as negative as -60 mV at 6 mM glucose, (89), but is between -50 and -40 mV at 10 mM glucose or above (52) (Figure 6 and schematic in Figure 13C-D).”