Fig 1. Glucose-stimulated insulin secretion in isolated islets assessed in a dynamic perifusion system.

Twenty handpicked islets were sequentially perifused with low (1.67 mM) glucose during minutes 1–48, high (20 mM) glucose during minutes 48–90, and then low glucose again during minutes 90–120. Fractions were collected at 6-min intervals, and the secreted insulin was measured by ELISA. The stimulation index (ratio mean secretion at high glucose vs. mean secretion at low glucose) for each donor is shown in (A). In (B) the concentration of insulin in the collected fractions is shown, and the dynamic stimulation index at each time point is displayed in (C). The dynamic stimulation index at each time point was calculated by normalizing the insulin concentration in each fraction to the mean basal insulin secretion at low glucose from the same islet sample. Data available from 1/8 adolescents, 4/6 young adults, 6/8 middle-aged. 4/6 elderly.