Fig. 2.

Differentiated neuronal cells do not release IDE into their medium. A, B, Differentiated PC12 cells (A) or 21 d primary mixed cortical cultures (B) were conditioned for 12 hr before the CM were collected and incubated for up to 24 hr with 300 pm IAβ.C–E, Undifferentiated PC12 culture medium that had been conditioned for 12 hr was similarly incubated with 300 pmIAβ in the absence (C) or presence (D) of 10 μm insulin or with 1 mm 1,10-phenanthroline (E).F, Whole cultures of undifferentiated PC12 cells were incubated with 300 pm IAβ in the absence of insulin. Aliquots of the CM were removed at the times indicated, and loss of intact IAβ was assayed by TCA precipitation. Curvesrepresent means (± SEM) of n = 4 experiments