Voltage-Activated Ca²⁺ and K⁺ Currents in an Insulin-Secreting Cell Line (RINm5F)

Abstract

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⁺ solutions^11,13. 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.