APOE and atherosclerosis: To test this hypothesis and to avoid the possibility that impaired acidification could be secondary to the reduced atherosclerosis or diminished lesion macrophage accumulation in Apoe–/–Nhe1+/– mice (Fig. 2a, b), we chose aortic segments with comparable lesion sizes and macrophage content between the Apoe–/–Nhe1+/+ and Apoe–/–Nhe1+/– mice that had been fed an atherogenic diet for 3 months.