MX1Cre-mediated recombination of the conditional alleles. MX1Cre-mediated recombination was determined 12 weeks after pI:pC induction: (1) by detecting β-galactosidase activity on cryosections of liver (A), spleen (B), and aorta (C) of MX1Cre transgenic mice that had been combined with Cre-reporter mice; (2) by immunoblotting membrane proteins isolated from livers of LRP^flox/floxLDLR^–/–APOE^–/– (D, left 2 lanes) and MX1Cre⁺LRP^flox/floxLDLR^–/–APOE^–/– (D, right 2 lanes) mice and subsequent staining with a polyclonal rabbit anti-LRP; and (3) by immunofluorescent detection of LRP and PDGF receptor in the descending aorta of LRP^flox/floxLDLR^–/–APOE^–/– (E,G) and MX1Cre⁺LRP^flox/floxLDLR^–/–APOE^–/– (F,H) mice.