A method for the simultaneous measurement of insulin release and B cell membrane potential in single mouse islets of Langerhans.

A method has been developed for the simultaneous measurement of insulin release and electrical activity in single micro-dissected mouse islets of Langerhans. The effects of D-glucose have been studied in individual islets. Each islet was exposed to 0, 5.6, 11.1, 16.7, 22.2, 27.8, and 33.3 mmol/l glucose in a stepwise fashion. The minimum glucose concentration required to elicit spike activity is lower than that required to stimulate insulin release above basal levels and the maximum spike frequency occurs at a lower glucose concentration than does maximum insulin release. Following a reduction in glucose from 27,8 (or 33.3) to 5.6 mmol/l, membrane potentials returned to resting values within 2 min whereas insulin returned to basal values after 20 min. Increasing glucose from 5.6 to 27.8 mmol/l induced spike activity within 10 s; the insulin response was detected within 40 s. Thus, it is possible to use the single mouse islet for simultaneous measurements of insulin release and electrical activity.