Electrophysiological properties of human β-cell lines EndoC-βH1 and -βH2 conform with human β-cells
Hastoy B., Godazgar M., Clark A., Nylander V., Spiliotis I., van de Bunt M., Chibalina M., Barrett A., Burrows C., Tarasov A., Scharfmann R., Gloyn A., Rorsman P.
The electrophysiological and secretory properties of the human β-cell lines EndoC-βH1 and EndoC-βH2 were investigated. Both cell lines respond to glucose (6-20mM) with 2-to 3-fold stimulation of insulin secretion, an effect that was mimicked by tolbutamide (0.2mM) and reversed by diazoxide (0.5mM). Glucose-induced insulin release correlated with an elevation of [Ca 2+ ] i , membrane depolarization and increased action potential firing. K ATP channel activity at 1mM glucose is low and increasing glucose to 6 or 20mM reduced K ATP channel activity to the same extent as application of the K ATP channel blocker tolbutamide (0.2mM). The upstroke of the action potentials in EndoC-βH1 and −βH2 cells observed at high glucose principally reflects activation of L- and P/Q-type Ca 2+ channels with some small contribution of TTX-sensitive Na + channels. Action potential repolarization involves activation of voltage-gated Kv2.2 channels and large-conductance Ca 2+ -activated K + channels. Exocytosis (measured by measurements of membrane capacitance) was triggered by membrane depolarizations >10ms to membrane potentials above -30mV. Both cell lines were well-granulated (6,000-15,000 granules/cell) and granules consisted of a central insulin core surrounded by a clear halo. We conclude that the EndoC-βH1 and -βH2 cells share many features of primary human β-cells and that they represent a useful experimental model.