Figure 4.

Milrinone prevents the inhibitory effect of IGF-1 on insulin secretion. The newborn rat pancreatic monolayer cells were cultured in low-glucose medium before transfer to high-glucose medium (see the legend of Fig. 2.). Different pharmacological conditions are represented by patterns or stippling. Milrinone, a highly selective inhibitor of PDE3B (IC₅₀ = 0.3 μM), potentiates insulin secretion at low concentration (1 μM), suggesting the presence of PDE3 activity. Although IGF-1 significantly suppressed insulin secretion in the absence of milrinone, it could not inhibit insulin secretion in its presence.