Year-end Sale % OFF 
Abstract
The turnover of free cholesterol in atheromatous plaque lipid phases was studied in a patient undergoing peripheral vascular surgery. [14C]Cholesterol was injected intravenously 139 days prior to surgery, and [3H]cholesterol was injected 12 days pre-op. The plasma cholesterol specific radioactivity decay curves were determined from the times of isotope injection until surgery. At surgery, atheroma, skin, muscle, and tendon were obtained. Lipid phases of plaque homogenate were isolated by density gradient centrifugation. The top layer of the gradient, layer 1, contained the cholesteryl ester oil droplet phase, layer 2 was enriched in phospholipid bilayer phase, layer 3 contained cholesterol monohydrate crystals and the pellet, layer 4 had more dense plaque components such as collagen and elastin. The tissue:plasma specific radioactivity ratios on days 12 and 139 respectively were muscle, 0.86, 2.47; skin, 0.74, 1.20; tendon, 0.18, 1.45; total plaque, 0.22, 1.39; plaque layer 1, 0.31, 1.50; layer 2, 0.22, 1.53; layer 3, 0.08, 0.61; and layer 4, 0.20, 0.88. Thus, plaque atheroma, which contains physically distinct forms of cholesterol, had correspondingly different rates of cholesterol turnover. Cholesterol solubilized in liquid oil droplets (layer 1) and liquid crystalline phospholipid bilayers (layer 2) had specific radioactivity values similar to those of tendon cholesterol, and represented tissue cholesterol that was undergoing slow equilibration with the plasma cholesterol pool. Pellet cholesterol (layer 4), which is probably connective tissue-associated, had lower specific radioactivity values, well below those of plasma cholesterol even after 5 months. Crystalline cholesterol (layer 3) had the lowest specific radioactivity values of all tissues and plaque fractions. Therefore, cholesterol in the crystalline state is relatively inert. Since crystalline cholesterol can account for over 40% of plaque free cholesterol, resistance to mobilization of this lipid may be an important obstacle to plaque regression.
Highlights
The turnover of free cholesterol in atheromatous plaque lipid phases was studied in a patient undergoing peripheral vascular surgery. [''C]Cholesterol was injected intravenously 139 days prior to surgery, and [3H]cholesterol was injected 12 days pre-op
From these data the parameters of the three-pool model of body cholesterol turnover were determined as follows: production rate (PR) = 1.17 g/day; the size of the rapidly turning over pool 1 (MI) = 21.4 g; the rate constants for transfer between pool 2 or 3 and pool 1, in days-': k12 = 0.129, k21 = 0.033, k13 = 0.027, and k31 = 0.049
As discussed previously (8, lo), pool 2 consists of cholesterol that equilibrates at an intermediate rate
Summary
The turnover of free cholesterol in atheromatous plaque lipid phases was studied in a patient undergoing peripheral vascular surgery. [''C]Cholesterol was injected intravenously 139 days prior to surgery, and [3H]cholesterol was injected 12 days pre-op. Cholesterol solubilized in liquid oil droplets (layer 1) and liquid crystalline phospholipid bilayers (layer 2) had specific radioactivity values similar to those of tendon cholesterol, and represented tissue cholesterol that was undergoing slow equilibration with the plasma cholesterol pool. Human atheroma contains free cholesterol in at least four lipid phases [7]: z) solubilized in cholesteryl ester oil droplets; z z ) solubilized in phospholipid bilayers; 2;;) crystallized as cholesterol monohydrate; and iu) associated with non-lipid tissue components such as elastin or collagen. In order to explore this question, we have used density gradient centrifugation of plaque homogenate to isolate the different lipid phases of surgically resected human atheroma [7] in a patient previously injected with radioactive cholesterol. By injecting two different isotopes at different times, information was obtained about the relative turnover rates of plaque and tissue free cholesterol compared to that of cholesterol in plasma
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
