In vivo influx of free and esterified plasma cholesterol into human aortic tissue without atherosclerotic lesions.

Abstract

A s bstract. In order to determine the in vivo influx of plasma cholesterol into human aortic intimamedia tissue, specimens of the ascending aortic wall without visible atherosclerosis were obtained from patients undergoing aortic valve replacement. Before the operation the patients were intravenously injected with autologous plasma in which the lipoproteins were labeled with radioactive cholesterol. The influence ofthe duration of the exposure time (0.3-114 h) and of the distribution of radioactivity between free and esterified cholesterol in plasma on the amount of radioactivity found in the arterial wall was studied by the simultaneous use of 3H-and '4C-cholesterol. It was shown that the influx of free and esterified cholesterol into the intima-media layer of the tissue could be calculated from a set of linear equations that relate the labeled sterols in the tissue to the average specific activities in plasma. In nine patients between 50 and 70 yr of age with 4.2-5.9 mM total cholesterol in plasma, the influx of free cholesterol and of esterified cholesterol was 1.2-8.8 and 1.0-12.5 nmol X cm-2 X d-', respectively. Both hydrolysis and esterification of the sterol fractions in the aortic tissue and exchange of free cholesterol between the plasma lipoproteins and the tissue were demonstrated. The cholesterol content of the intima-media layer was 0.6-2.3 Mumol X cm-2. This corresponds to the influx of esterified cholesterol during a period of only 0.1-3.5 yr, which is short compared with the lifespan of the patient. Our data thus suggest that removal of esterified cholesterol from aortic tissue without visible atherosclerosis repre-

Fate of fibrinogen in human arterial intima.

“…In patients undergoing aortic valve replacement, studies of ascending aorta suggest that a high proportion of the cholesterol that enters the wall effluxes again. 30 In rabbits, Carew et al 31 estimated that 70% to 75% of the aortic LDL flux must be bi-directional.…”

Triglyceride-Rich Lipoproteins and Atherosclerotic Cardiovascular Disease

“…[86][87][88][89][90][91] LDL can also leave the intima again, 88,[92][93][94] but only through the lumen against the pressure gradient generated from blood pressure, whereas LDL particles are too large to penetrate the elastic laminas of the media. 94,95 In other words, LDL gets trapped in the arterial intima and attachment to proteoglycans, or other components of the arterial intima may further facilitate LDL trapping within the intima.…”

Different efflux pathways for high and low density lipoproteins from porcine aortic intima.

“…4 The cholesterol content in arterial intima without atherosclerotic lesions of 50-to 70-year-old humans is equivalent to less than 4 years of cholesterol influx. 5 Thus, since the cholesterol molecule cannot be degraded by arterial tissue, the major part of cholesterol that enters arterial intima has to leave the arterial wall again.…”