Apolipoprotein B (apoB) retention in atherosclerotic intracranial arteries.

Low (LDL) and very low (VLDL) density lipoproteins retained in grossly normal and atherosclerotic human intracranial arteries have been quantitated using an electro-immunoassay directed against apolipoprotein B (apoB), the major protein of these two lipoprotein fractions. Buffer-homogenates of grossly normal arteries contained apoB amounts ranging from less than 0.04 to 1.58 microng/mg tissue dry weight, while those of atherosclerotic plaques gave values ranging from 0.80 to 3.9 microng per mg tissue dry weight. These results were consistent with immunofluorescence studies localizing apoB in these arteries. Plaques also contained a remaining fraction of tightly-bound apoB as evidenced by positive immunofluorescence in sections of pellets from buffer homogenates. This was in contrast to the negative results from grossly normal arteries. These results would suggest that retention of apoB by intracranial arteries correlates positively with vessel lesions. Arterial apoB is present in both grossly normal regions and plaques in a loosely-bound form, possibly representing intact lipoprotein. ApoB is also present in a tightly-bound form in plaques.