Figure 5.

IGF-1 suppresses insulin secretion from HIT-T15 cells. HIT-T15 cells were perifused by Krebs–Ringer buffer containing 0.1% BSA and no glucose until the basal insulin level became stable. The perifused cells were then switched to the same buffer containing high glucose with or without the other agents. The starting point of exposure to high-glucose medium is indicated by the arrow. The results shown here are the average of fractions from duplicate columns. IGF-1 consistently suppressed insulin secretion both with and without 8-Br-cAMP potentiation.