Voltage-Activated Ca2+ and K+ Currents in an Insulin-Secreting Cell Line (RINm5F)
A cloned and continuous line of cells of islet derivation is a useful tool for studies which require large quantities of homogenous cellular material. The RINm5F cell line was developed from an insulinoma induced initially in a rat and then transplanted through mice before being established as a continuous cell line7. The secretion of insulin by RINm5F cells can be stimulated by secretagogues such as glyceraldehyde and L-alanine and by exposure to high K+ solutions11,13. Though interestingly insulin secretion is not enhanced by the β-cell secretagogue, glucose11. Although numerous biochemical studies of these cells have been made their electrophysiology is unknown and there is therefore no comparison with the body of literature concerning the electrophysiology of β-cells. Elsewhere in this volume10 we have shown, using patch-clamp electrophysiological techniques, that RINm5F cells maintain a stable negative membrane potential and that upon exposure to a secretagogue RINm5F cells depolarise and fire spike-potentials. In this study we examine in more detail the spike potentials and show them to result from voltage-activation of Ca-channels.
KeywordsMembrane Current Voltage Step Membrane Voltage Islet Cell Tumor RINm5F Cell
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