Ma. Wahl et al., OXIDATIVE STRESS CAUSES DEPOLARIZATION AND CALCIUM-UPTAKE IN THE RAT INSULINOMA CELL RINM5F, EXPERIMENTAL AND CLINICAL ENDOCRINOLOGY & DIABETES, 106(3), 1998, pp. 173-177
Generation of free radicals and oxidative stress play a role in the de
velopment of islet dysfunction in diabetes. These mechanisms are known
to affect membrane potential and cytosolic calcium in other cell type
s. The effect of oxidative stress, caused by tert-butyl-hydroperoxide
(BuOOH), was therefore studied with respect to the redox ratio of glut
athione, membrane potential, cytosolic calcium and insulin release in
the insulin-secreting RINm5F cell. In RINm5F cells BuOOH decreased the
redox ratio of glutathione and caused depolarization. This was associ
ated with an increase in cytosolic calcium and insulin secretion. The
effects of BuOOH on cytosolic calcium and insulin release were abolish
ed in the absence of extracellular calcium and decreased by the calciu
m channel blocker verapamil. Our data suggest that in RINm5F cells oxi
dative stress causes insulin release by depolarization and subsequent
calcium entry through voltage-dependent calcium channels.