Dual effects of glucose on the cytosolic Ca2+ activity of mouse pancreatic β‐cells

Abstract

The cytosolic Ca²⁺ activity of mouse pancreatic β-cells was studied with the intracellular fluorescent indicator quin2. When the extracellular Ca²⁺ concentration was 1.20 mM, the basal cytosolic Ca²⁺ activity was 162 ± 9 nM. Stimulation with 20 mM glucose increased this Ca²⁺ activity by 40%. In the presence of only 0.20 mM Ca²⁺ or after the addition of the voltage-dependent Ca²⁺-channel blocker D-600, glucose had an opposite and more prompt effect in reducing cytosolic Ca²⁺ by about 15%. It is concluded that an early result of glucose exposure is a lowering of the cytosolic Ca²⁺ activity and that this effect tends to be masked by a subsequent increase of the Ca²⁺ activity due to influx of Ca²⁺ through the voltage-dependent Ca²⁺ channels.