Potassium-induced insulin release and voltage noise measurements in single mouse islets of Langerhans

Summary Insulin release and membrane potential fluctuations in response to increased extracellular potassium [K⁺]_o have been measured in single perifused islets of Langerhans from normal mice. An increase in [K⁺]_o from 5mm to 50mm induced a transient insulin release with a peak at about 1 min. The peak value was [K⁺]_o-dependent but the half-timet_1/2 for the decline was constant at nearly 1 min. 2.5mm cobalt completely inhibited the potassium-induced stimulation of insulin release. The insulin release elicited by 28 and 50mm [K⁺]_o was similar in terms of peak, total release and half-time from maximum release. Stepwise increase in [K⁺]_o from 10 to 28 to 50mm resulted in a normal response to 28mm but no peak of release after the 28 to 50mm increase. The results indicate good correlation between excess voltage noise, thought to reflect calcium channel activity, and insulin release evoked by changing extracellular potassium.