Electrophysiological evidence for the autoregulation of beta-cell secretion by insulin

Electrophysiological studies of cultured rat pancreatic beta-cells using intracellular microelectrodes show that exogenous insulin over the range of 0.1 -- 10.0 microng/ml inhibits the electrical activity due to 27.8 mM glucose in a dose-related manner. This inhibitory effect is manifested by a mean increase of the membrane potential from about --20 to --30 mV and inhibition of the number of cells impaled showing spike activity from 60 to less than 10%. The inhibitory influence of insulin is rapid occurring within 5 min for the highest level used. The results provide evidence for a negative feedback role of insulin in regulating its own release.