Figure 4. Interactions between E2 and IGF-I. (A) Uptake of biotinylated IGF-I (bIGF-I) by brain endothelial cells obtained from young female mice (2 months-old) is increased by estradiol (E2) acting through E2Rα. Note that only the ERα agonist PPT, but not the ERβ agonist DPN, mimics the actions of E2. Representative blots are shown at the right. β-actin was measured as a loading control (n=6). (B) Estradiol does not stimulate uptake of bIGF-I in brain endothelial cells obtained from middle-aged female mice (n= 4). (C) Levels of ERα mRNA were reduced in brain endothelia from middle-aged female mice (n=4). (D) Levels of IGF-IR mRNA remain unaltered in brain endothelia in middle-aged female mice compared to young mice (n=9-10). (E) Co-immunoprecipitation of ERα with IGF-IR showed a significantly decreased interaction in response to E2 in brain endothelial cells obtained from middle-aged female mice (n=4). Representative blot of an immunoprecipitation using anti-ERα is shown. NIS: non-immune serum. *p<0.05 vs respective control.