Accumulation of HIF2α protein in the kidneys of IRP1^−/− mice is age dependent. (A) (Left) Western blots of IRP1, HIF2α, and β-actin in kidneys of 6-week-old WT and IRP1^−/− mice (n = 4). (Right) Densitometric quantification of HIF2α expression. (B) (Left) Comparative western blot and (right) densitometric quantification of HIF2α expression in kidneys of 6-week- and 6-month-old IRP1^−/− mice (n = 4). *P < .05; ***P < .001.