Inhibition of PRL gene expression and release by insulin from differentiated primary sc adipocytes (A and C) and LS14 cells (B and D). Primary preadipocytes (pooled from several patients) and LS14 cells were induced to differentiated as detailed in Subjects and Methods. On d 10–12 of differentiation, cells were first incubated for 24 h in DMEM/F10 medium containing 1% CSS, and then incubated for an additional 24 h with various doses of insulin or IGF-I. CM were analyzed for PRL by the Nb2 bioassay (A and B), and isolated RNA was analyzed for PRL expression by real-time PCR (C and D). Each value is the mean ± sem of four to six replicates. *, P < 0.05 change with respect to controls. Shown are representative experiments, each repeated three times.