Quantitation of apo b in human aortic fatty streaks A comparison with grossly normal intima and fibrous plaques

The content of apolipoprotein B (apo B)-containing lipoproteins was measured in aortic fatty streak lesions of 18 male individuals between the ages of 21 and 67 years, and compared to the values found in adjacent grossly normal intima. Extraction of apo B was accomplished by sequential treatment of aortic tissue homogenates with a standard buffer and one containing the detergent Triton X-100. Mean apo B values (μg per mg tissue dry weight) in fatty streaks were: buffer-extracted = 4.67 ± 0.51, Triton-extracted = 1.88 ± 0.39; while in adjacent grossly normal intima: buffer-extracted = 6.51 ± 0.92, Tritonextracted = 0.37 ± 0.15. Using a paired t-test, buffer-extracted apo B was marginally significantly greater in the adjacent normal intima than fatty streaks (P < 0.05), whereas Triton-extracted apo B was highly significantly greater in fatty streaks than adjacent normal intima (P < 0.0005). When the mean apo B values of these 18 fatty streaks and 23 fibrous plaques from separate cases were compared in a non-paired t-test, buffer-extracted apo B was slightly higher in fatty streaks than fibrous plaques (P < 0.025), whereas Triton-extracted apo B was much higher in fibrous plaques than in fatty streaks (P < 0.0005). The intermediate position of fatty streaks between grossly normal and fibrous plaques with respect to buffer- and Triton-extracted apo B content, gives additional support to the contention that this lesion is an intermediate step in the progression of the grossly normal intima to a fibrous plaque. Assuming this sequence of progression to occur, our results demonstrate a marginally significant decrease in buffer-extracted apo B but a highly statistically significant increase in Triton-extracted apo B with lesion development.