CORRELATIONS OF RATES OF INSULIN RELEASE FROM ISLETS AND PLATEAU FRACTIONS FOR BETA-CELLS

Pancreatic beta-cells in intact islets of Langerhans perfused with var ious glucose concentrations exhibit periodic bursting electrical activ ity (BEA) consisting of active and silent phases. The fraction of the time spent in the active phase is called the plateau fraction and appe ars to be strongly correlated with the rate of release of insulin from islets as glucose concentration is varied. Here this correlation is q uantified and a theoretical development is presented in detail. Experi mental rates of insulin release are correlated with ''effective'' plat eau fractions over a range of glucose concentrations. There are a numb er of different models for BEA in pancreatic beta-cells and a method i s developed here to quantify the dependence of a glucose dependent par ameter on glucose concentration. As an example, the plateau fractions computed from the Sherman-Rinzel-Keizer model are matched with experim ental plateau fractions to obtain a relationship between the model's g lucose-dependent parameter, beta, and glucose concentration. Knowledge of the relationships between beta and glucose concentration and betwe en experimental measurements of rates of insulin release and plateau f ractions permits the determination of theoretical rates of insulin rel ease from the model.