Tissue inhibitor of metalloproteases (TIMP) is matrix associated in aortic tissue: report of a radioimmunoassay

Tissue inhibitor of metalloproteinases (TIMP) is the major inhibitor of collagenase, gelatinase, proteoglycanase, stromelysin, and metalloelastases. An imbalance between proteases and inhibitors has been implicated in numerous disease processes including tumor invasion, rheumatoid arthritis, emphysema, and aortic aneurysm disease. The purpose of this investigation was to develop a polyclonal antibody to recombinant TIMP and establish an immunoassay to measure immunoreactive protein in normal and diseased tissues. A polyclonal antibody was produced in rabbit against recombinant human TIMP which was characterized and used to establish a radioimmunoassay. The assay was used to measure immunoreactive protein in fibroblast conditioned medium, human serum, and aortic extracts. There was more immunoreactive TIMP in matrix associated urea extracts than soluble salt extracts from human aorta, suggesting that TIMP is matrix associated. The sensitivity of the assay enables the specific measurement of this inhibitor in serum, fibroblast culture medium, and tissue extracts.

LDL accumulation in the grossly normal human iliac bifurcation and common iliac arteries

We had previously used an electrophoretic transfer procedure to determine the topographic distribution of low density lipoprotein (LDL) accumulation in the aortic intima of normolipemic swine. In this present study we have employed a similar procedure to assess whether LDL-rich sites consistently demonstrate increased intimal thickening at the iliac bifurcation and common iliac arteries. The topographic distribution of LDL-rich sites was determined in the aortas of six subjects ranging in age from 16 to 36 years, by transferring LDL by electrophoresis from the tissue into an agarose gel containing anti-LDL, and then staining the immunofixed LDL in the gel for lipid. LDL-rich sites were found in all but two of these cases. On the basis of control studies establishing the level of nonspecific staining, we determined that the cutoff between LDL-rich and LDL-poor zones was 37 mg apoB protein/mm2 intimal surface area. Intimal thickening was found to be threefold greater in LDL-rich than in LDL-poor regions. These results confirm and extend earlier immunohistochemical studies suggesting a preferential accumulation of LDL at sites of intimal thickening in human arteries.

Chemical shift magnetic resonance imaging of human atheroma

Fifteen necropsy specimens of human descending aorta and from eight patients with atheromatous vascular disease were studied by magnetic resonance imaging at 0.5 T. Images were acquired in coronal and transverse planes to localised protruding lesions and then chemical shift imaging was performed by techniques described by Dixon and by Hinks. These techniques produce images in which signal strength is proportional to lipid content. The signal was expressed as a percentage of that from extravascular fat. The total lipid content and its distribution within the plaques were noted. After imaging, the postmortem specimens were examined histologically and the lipid content of the plaque was assessed on a semiquantitative scale. The distribution of lipid within the plaque and between intima and media was also noted. The findings of chemical shift imaging agreed well with histological examination both for total lipid content and for distribution within each plaque. Chemical shift imaging also provided an assessment of the lipid content of the plaques measured in living patients, but validation was more difficult. The usefulness of the technique in routine clinical practice remains to be established.

Limitations of the lipid state hypothesis for atherosclerosis are revealed by X-ray diffraction measurements

The lipid state hypothesis proposes that liquid crystalline states of cholesteryl esters play a role in the development and persistence of the fatty streak lesions characteristic of atherosclerosis. We have tested several corollaries suggested by this hypothesis and find that the ensemble of droplets in atherosclerotic tissue are predominantly in the isotropic (fluid) state at 37.0 degrees C. Furthermore, the liquid-crystalline state transition behavior of these droplets is not influenced significantly by the distribution of component cholesteryl ester species. There are no significant correlations between the transition behavior of the droplets and the age, sex, or race of the subjects from which tissue samples were taken. These results show that the lipid state hypothesis is weak, and that the origin and persistence of fatty streak lesions in humans is probably dominated by other factors.

Calcitonin gene-related peptide (CGRP) in normotensive and spontaneously hypertensive rats

With the techniques of specific radioimmunoassay and gel filtration it was found that CGRP was distributed in various tissues of normotensive (WKY) and spontaneously hypertensive rats (SHR) with the highest concentration in the lumbar spinal cord (1197 +/- 94.8 pg/mg tissue) and the lowest in the auricle (15.0 +/- 2.1 pg/mg tissue). In comparison with WKY, CGRP concentration in the plasma was decreased and in the abdominal aorta and hypothalamus was increased in SHR. Gel filtration revealed only one major CGRP molecular form in the tissues. In addition, CGRP reduced the mean arterial pressure (MAP) in SHR in a dose-dependent manner. These data suggest that CGRP may play an important role in the pathogenesis of hypertension and its possible therapy.

Cellular, enzymatic, and genetic factors in the pathogenesis of abdominal aortic aneurysms

Aneurysms of the abdominal aorta occur with atherosclerosis or connective tissue disorders. Changes of three components of aortic media, smooth muscle cells, elastin, and collagen, which could contribute to medial weakening, are discussed. Smooth muscle cells cultured from the aging abdominal aorta (normal, atherosclerotic, or aneurysmal) have limited replicative potential at five to six cell doublings, whereas cells from aneurysmal thoracic aorta undergo more than 20 cell doublings in culture. The elastin content is much reduced in aneurysms and this is associated with an increase in elastase activity of medial homogenates to 17.8 U/ng of deoxyribonucleic acid (DNA) compared with 8.3 and 4.4 U/ng of DNA in atherosclerotic and normal aorta, respectively. An elastinolytic enzyme has been purified from aneurysmal aorta and appears to have different properties from human leukocyte elastase. Ruptured aneurysms are associated with an increased total collagenase activity but the increase could be stimulated by, or result from, an influx of inflammatory cells and does not necessarily have a causal significance. In patients with a family history of aneurysm there appears to be a decreased content of type III collagen in aortic media: 24% +/- 4% compared with 32% +/- 5% in most aneurysms. Familial aneurysms are most common in women, and preliminary results suggest that a polymorphic variant of the type III collagen gene, defined by restriction enzyme digest, may be associated with aneurysmal disease in women. The genetic approach may define causal mechanisms predisposing patients to aneurysmal dilatation.

Large lipoproteins are excluded from the arterial wall in diabetic cholesterol-fed rabbits

In diabetic hypercholesterolemic rabbits at plasma triglyceride concentrations of approximately 5000 mg/dl, 55% of plasma cholesterol (1400 mg/dl) was in lipoproteins with diameters larger than 75 nm (Sf greater than 400), 40% in smaller very low density and intermediate density lipoproteins, 4% in low density lipoproteins, and 1% in high density lipoproteins. Specific intimal clearance (nl/h.mg aortic cholesterol) of the giant Sf greater than 400 lipoproteins was about 4% of that of the low density lipoproteins. The data suggest that even very low density lipoproteins with diameters smaller than 75 nm were practically excluded from entering the arterial wall. Specific intimal clearance of low density lipoproteins in hypertriglyceridemic, diabetic cholesterol-fed rabbits was similar to that in normal cholesterol-fed rabbits, but low density lipoprotein concentrations in diabetic rabbits were low. Thus, at plasma triglyceride concentrations of approximately 5000 mg/dl, only 5% of plasma cholesterol may be readily available for infiltration of arteries. These results add further support to the hypothesis that hypertriglyceridemic, diabetic cholesterol-fed rabbits are protected against atherogenesis because the major part of plasma cholesterol is carried in large lipoproteins to which the artery is not very permeable.

Characterization of the phenotype of smooth muscle cells in human fetal aorta on the basis of ultrastructure, immunofluorescence, and the composition of cytoskeletal and cytocontractile proteins

The phenotype of smooth muscle cells (SMCs) in the aortic media of 7 human fetuses (14-20 weeks of gestation) was examined with transmission electron microscopy, immunofluorescence microscopy, and gel electrophoresis of the cytoskeletal and cytocontractile proteins. Ultrastructurally, virtually all medial cells were identified as SMCs having a poorly differentiated phenotype with a cytoplasm rich in rough endoplasmic reticulum and organelles, and with only a few myofilaments. All medial cells stained intensely with antibodies to vimentin, but only in a 20-week-old fetus could we find a few SMCs staining with antibodies to desmin. Nor was desmin detectable with SDS gel electrophoresis followed by immunoblotting, while clear bands corresponding to vimentin, myosin, and actin were present. In isoelectric focusing and two-dimensional gel electrophoresis beta-actin was the most prominent of the 3 actin isoforms in all cases. The present results show that SMCs in the media of fetal human aorta have a poorly differentiated phenotype, which morphologically and biochemically resembles that previously described in the aorta of fetal and newborn rat, in the arterial intima after endothelial injury, in atherosclerotic lesions, and after spontaneous modulation of medial SMCs in culture.

Proteoglycan distribution in the intima and media of the aortas of young and aging rabbits: an ultrastructural study

Aortas from normal healthy rabbits, approx. 3 months old, were examined by light and transmission electron microscopy. The proteoglycan of the extracellular matrix, which was stained by ruthenium red and appeared as granules by transmission electron microscopy, was quantitated morphometrically in the intima and the superficial media. The intima included areas which were thickened and which contained connective tissue, including proteoglycan, and some smooth muscle cells. In the thickened intima there was a greater proportion of extracellular space which was occupied by proteoglycan, and the proteoglycan was present in higher concentration than in the media. In the aortas of rabbits, approx. 2 years old, the extent of intimal thickening and the concentration of proteoglycan increased in the thickened intima but there was no evidence of extracellular lipid deposition. The endothelial basement membrane contained small proteoglycan granules (heparan sulphate) which decreased in concentration in older animals. It is possible that the accumulation of proteoglycan in the thickened intima increases the susceptibility of the intima to accumulate lipid following an additional stimulus, such as hyperlipaemia, in the initial stages of atherosclerosis.

Renal vein immunoreactive renin in patients with renal artery stenosis and essential hypertension

In 36 patients with unilateral renal artery stenosis and in 24 with essential hypertension the plasma levels of total immunoreactive renin, and enzymatically active renin were measured in both renal veins (V) and in the aorta (A) by direct RIA by using monoclonal renin antibodies. Active renin and trypsin-activatable inactive renin were also measured by indirect RIA with angiotensin-I antibodies. The V/A ratio for the different forms of renin calculated from the results of direct and indirect RIA were not different. The V/A ratio of active renin for the kidney with the stenotic artery was 3.04 +/- 0.28 (mean +/- sem) with direct and 3.02 +/- 0.25 with indirect RIA. The contralateral ratio was 1.04 +/- 0.02 with the direct and 1.05 +/- 0.02 with the indirect RIA. In essential hypertension it was 1.28 +/- 0.04 with direct RIA and 1.28 +/- 0.04 with indirect RIA. Chronic treatment with captopril had no influence on this ratio in both patients groups. The V/A ratio of total immunoreactive renin was lower than that of active renin and this ratio had lost discriminative power for lateralization. This ratio was significantly greater than one on the affected side in renal artery stenosis but not contralaterally and in essential hypertension. This study shows that renin activity after trypsin-activation of plasma is an accurate measure of the total renin concentration, i.e. active renin plus prorenin. It also shows that a kidney with a stenotic artery secretes inactive renin, which is immunologically related to active renin and is likely to be prorenin. Direct RIA for measuring active renin is technically more simple than indirect RIA. Direct RIA however is somewhat less sensitive. For measuring the V/A ratio for active renin in patients with renal artery stenosis this can be overcome by stimulating the renin-angiotensin system for instance by captopril.

Cellular changes during hypertension: a quantitative study of the rat aorta

Using rats made hypertensive by aortic ligation or by the one kidney--one clip method, we searched the aorta for morphologic clues that could explain why hypertension aggravates atherosclerosis. Both atherosclerosis and hypertension are characterized by an increased migration of mononuclear cells into the aortic intima; we therefore quantitated this phenomenon and studied its time course. In the thoracic aorta of hypertensive rats intimal cells (emigrated mononuclear cells) increased up to 15 times 2 weeks after surgery and remained stationary thereafter. In both control and experimental rats, leukocyte emigration was heavier in the thoracic aorta than in the abdominal region. A two- to threefold increase in medial smooth muscle herniae into the intima (myointimal herniae) was also found at 8 weeks, indicating a smooth muscle cell dysfunction. Electron microscopic study of the intima showed that its thickening was due to blood-borne material and also to extracellular matrix synthesized by the endothelium. Heightened secretion reflects cell activation, a condition that (in the endothelium) leads also to leukocyte adhesion. These data suggest that, in renovascular hypertension, the aortic endothelium is in an activated state, possibly through a hormonal stimulus.

Basic proteins in the human aortic intima: nonequilibrium two-dimensional electrophoretic analysis of tissue extracts

The protein composition of atheroma-free human thoracic intima was compared with that containing fatty streaks or fibro-fatty lesions utilizing two-dimensional gel electrophoresis (2-DE) and silver staining. Intimal proteins extracted with 9 M urea were separated by nonequilibrium pH gradient electrophoresis (NEPHGE) followed by polyacrylamide gel electrophoresis (PAGE) in the second dimension. NEPHGE-PAGE of proteins extracted from atheroma-free intima revealed several major proteins: actin, tropomyosin-like proteins, proteins with relative molecular weight (Mr) of 250,000 (P250), two proteins with Mr about 15,000 (P15a, P15b), and many medium proteins such as a myosin heavy chain, two myosin light chains, and proteins P47, P44, P32, P27, P20a, P20b, P19a, P19b. Several additional proteins were observed in intimas with fatty streaks and fibro-fatty lesions. Most of them, such as albumin, transferrin, Apo A-I, alpha 1-antitrypsin, fibrinogen beta-chain, IgG, appear to originate from plasma. Differences in protein composition of intima with fibro-fatty streaks compared with adjacent lesion-free intima varied from case to case and need further study. NEPHGE-PAGE in combination with isoelectric focusing (ISO)-PAGE revealed more intimal proteins in atheroma-free and diseased aortas than either method alone, proteins which might be quantitated, isolated for binding studies, and further evaluated for their potential role in atherogenesis.

Spatial distribution and accumulation of low density lipoproteins in the abdominal aorta of swine: determination by a novel electrotransfer procedure

An immunotransfer procedure has been developed which can determine both the spatial distribution of low density lipoproteins (LDL) along the intima-media of large blood vessels such as the aorta, and can quantify LDL accumulation along its length. Aortas which were opened longitudinally along their ventral aspect were positioned so that their intimal side abutted against a gel containing glyoxyl agarose to which anti-LDL had been covalently coupled. LDL was electrophoresed out of the agarose gel where it was immunofixed. This distribution was then visualized first by incubating the gel with 125I-anti-LDL which bound to free epitopes on the immunofixed LDL, and second by subjecting the washed and dried gel to autoradiography. Plasma LDL was applied to wells of different shapes and sizes in an agarose gel substituting for aortic tissue, and the transfer procedure was performed as described. The resultant patterns matched those of the original wells, suggesting that the spatial distribution of LDL in the autoradiogram probably mimicked that in the aortic tissue. The transfer procedure appeared to be specific for the antigen under study since minimal silver grains were observed in autoradiograms when an IgG fraction of nonimmune serum was used in place of anti-LDL. Application of increasing concentrations of LDL to wells in a gel substituting for tissue, resulted in a dose-dependent increase in autoradiographic grain density. If such standards were applied to gels adjacent to tissue samples, the amounts of LDL in the tissue could be quantified from the standard curve of grain density versus LDL concentration. The distribution of LDL along the abdominal aortas of 10- and 31-week-old swine was determined by converting autoradiographic grain densities to isopleths of LDL concentrations by computer assisted image analysis. These distributions were focal and were found to range between 10 and 225 ng of apoB/mm2 of intimal surface area. This procedure lends itself not only to studies relating lipoprotein accumulation to atherogenesis, but also to any studies dealing with tissue accumulation of macromolecules.

Intermediate filament heterogeneity in normal and hypercholesterolemic rabbit vascular smooth muscle cells

We have examined the intermediate filament (IF) protein content of vascular smooth muscle (SM) cells from several arteries and veins in rabbits and quantitated the changes which occur in SM cell expression of these proteins in response to cholesterol feeding. Cells from control rabbit arteries expressed 30% of their IF protein as desmin, while veins expressed 50% as desmin. During development of diet-induced atherosclerosis, morphological changes in arterial SM cells in the intima correlate with changes in IF expression. There is a significant increase in total IF protein content, vimentin increased differentially in thoracic aorta and desmin in pulmonary artery. In abdominal aorta both increase equally. Cholesterol feeding also resulted in changes in the expression of subspecies of desmin, vimentin, and actin in the thoracic arch. Although cholesterol feeding did not produce obvious morphological changes in the veins examined, venous SM IF protein expression was also altered. In the vena cava of cholesterol-fed rabbits there was an increase in vimentin expression without the parallel increase in desmin that occurred in the arterial system. These studies show that cholesterol feeding of rabbits induces measurable changes in the amounts of IF proteins in both arterial atherosclerotic lesions and venous SM cells.

The static elastic properties and chemical composition of the rat aorta in spontaneously occurring and experimentally induced hypertension: the effect of an anti-hypertensive drug

The static elasticity and scleroprotein content of the aorta have been measured in 24 Okamoto spontaneously hypertensive rats aged 22-25 weeks, and 24 Wistars of the same age in which hypertension had been induced by nephrectomy and treated with a steroid. From the age of 4 weeks half the animals in each group were treated with a diuretic drug. By the age of 15 weeks caudal artery systolic blood pressure was significantly lower than control values in both drug-treated groups and remained so until death. Both types of hypertension were associated with larger diameter, thicker-walled and heavier aortas than those in the drug-treated animals. Vessels from Okamoto animals contained more collagen than those from the Wistars, although the collagen content was unchanged by drug treatment. Neither drug nor strain had any clear-cut affect on elastin content. In spite of these differences in wall thickness and chemical composition, values of the functional stiffness of the aorta measured over a wide range of pressure were similar in all four groups of animals. Using a simple model of the aorta in which elastin and collagen bear stress in parallel we find that the relationship between vessel composition and static incremental elastic modulus (structural stiffness) is similar in both models of hypertension and is not changed by drug treatment in spite of the consequent reduction in blood pressure.

An enzyme-linked immunosorbent assay to quantitate the elastin crosslink desmosine in tissue and urine samples

An enzyme-linked immunosorbent assay method has been developed for the determination of desmosine. The method is based on an inhibition immunoassay (under nonequilibrium conditions) and uses rabbit antisera directed against a desmosine-bovine serum albumin conjugate and microtiter plates coated with desmosine-gelatin conjugate. The assay quantitates desmosine in the range 2.5-50 pmol in tissue and urine samples. Important applications of this rapid and sensitive assay are in studying elastin metabolism and in screening for monoclonal antibodies against desmosine. Methods are described for obtaining a constant level of substitution of desmosine per molecule of bovine serum albumin and for preparing a desmosine-gelatin coating antigen. Five different antibody preparations directed against desmosine exhibit 15-20% cross-reactivity toward pyridinoline (3-hydroxypyridinium), a nonreducible collagen crosslinking compound also present in urine and many tissue samples.

The influence of age on fluid and sodium chloride distribution in rat aortic wall

Fluid, Na+ and Cl- content and distribution have been examined in incubated segments of thoracic and abdominal aorta from male Wistar rats aged 1, 3 and 18 months. Na+ and Cl- were determined under conditions of total metabolic blockade (cyanide + iodoacetate). The total aortic mural fluid content, relative to solute-free dry weight, fell from 1 to 3 months, due mainly to relative contraction of the extracellular (e.c.) (inulin) space. It increased from 3 to 18 months due mainly to an increased intracellular (i.c.) (non-inulin) space. Total mural free and bound Na+ content, as well as i.c. Na+ content and concentration, fell from 1 to 3 months and increased from 3 to 18 months. No bound Na+ was detectable in segments which had been incubated in the presence of chondroitinase ABC. I.c. Cl- content and concentration fell from 1 to 3 months, but thereafter did not alter significantly. Bound Cl- in the aortic wall of 3-month-old rats was markedly reduced by incubation in the presence of a non-specific protease preceded by treatment with glycerol. The results are discussed in relation to previously established age-related characteristics of aortic and arterial walls.

Apoprotein B quantification in rhesus and cynomolgus monkey atherosclerotic lesions

The concept that much of the cholesterol deposition in atherosclerotic plaque development is provided by ingress of blood-derived apo B-rich lipoproteins into the arterial intima is given support by the study of arterial apo B accumulation. To compare the arterial wall level of immunoreactive apo B during the progression of diet-induced atherosclerosis in two widely used animal models of atherosclerosis, rhesus and cynomolgus monkeys were fed an atherogenic diet for 4, 8, and 12 months and their abdominal aortas quantitated for apo B. Apo B was extracted from aortic intima-media homogenates in two forms: Tris-buffer extractable or 'loosely bounds' and detergent (Triton X-100) extractable or 'tightly bound'. The aortic extracts were quantitated for apo B by radial immunodiffusion, using goat anti-rhesus apo B along with serum LDL standards of the appropriate species diluted in the two extract solutions. The control monkeys' aortas contained only buffer-extractable apo B. The atherosclerotic aortas of both species of monkeys progressively increased their levels of loosely bound and tightly bound apo B through 4, 8, and 12 months of atherogenic diet feeding, with the 8- and 12-month cynomolgus aortas containing much larger amounts of apo B than the rhesus aortas. These differences in aortic apo B content could be accounted for by the greater rate at which the cynomolgus atherosclerotic lesions developed at the later time points. When the total lesion apo B levels were correlated with representative morphometrically-quantitated histopathologic sections of the homogenized aortas, a highly significant correlation was seen between the total aortic apo B values and both the absolute area of the intimal lesions and the total area of oil red O stainable lipid in the lesions (P less than 0.001). These data indicate that as atherosclerotic lesions become larger and richer in lipid with progression of the disease, the amount of apo B-associated lipoproteins which are deposited unmetabolized in the lesions increases. These lipoproteins are increased in both the tightly bound and loosely bound forms.

[Evidence for the existence of inactive arterial renin in the rat]

Inactive renin in rat arterial walls was investigated according to the following experiments. Dialysis at pH 7.4 following dialysis at pH 3.3 of the arterial tissue resulted in a significant rise of renin activity, from a control value of 0.41 +/- 0.07 to 0.62 +/- 0.06 ng/ml/h (p less than 0.01). Treatment with trypsin of the arterial tissue caused a rapid and apparent increase in the renin activity at either 0 or 27 degrees C. The molecular weight of the active renin was estimated to be 32,000 or 39,000, while that of the inactive renin was found to be 36,000 or 44,000 on Sephadex G-100 gel filtration. The contents of the inactive renin varied with different segments of arterial wall. The ratio of inactive renin to total renin was the lowest in renal artery wall (0.32), while there was no significant difference in the ratio in other arterial walls (abdominal aorta, 0.87; thoracic aorta, 0.93; carotid artery, 0.96; mesenteric artery, 0.89; pulmonary artery, 0.92). These findings suggest that conversion of inactive renin into active renin can occur in arterial tissue, which, in turn, plays an important role in the local control of vascular tone. It seems that inactive renin found in the arterial wall is of local origin.

Atherosclerosis and lipid composition of the abdominal aorta. Comparison of autopsied New Orleans and Guatemalan men

Abdominal aortas from 78 Guatemalan men and 79 New Orleans white men were examined for lipid composition and for the extent of grossly visible atherosclerotic lesions. In the specimens examined, atherosclerotic lesions were more extensive in New Orleans than in Guatemala, confirming findings of studies performed 10 and 20 years earlier. Lipid accumulation differed greatly between the geographic locations with new Orleans specimens having more chemically determined lipids. Differences in lipid accumulation between New Orleans and Guatemala are more striking when expressed in terms of content (milligrams per 100 square centimeters than when expressed as concentration (milligrams per gram of dry defatted weight). Chemical analyses indicate that lipid accumulation in the aorta results principally from the atherosclerotic process rather than from aging. In the 15- to 24-year age group, the gross extent of fatty streaks was similar in both populations, but content and concentration of free cholesterol was significantly higher in New Orleans specimens than in Guatemalan specimens. This finding might be related to the more extensive development of raised lesions at later ages in New Orleans subjects.

Uneven distribution of sialic acids on the luminal surface of aortic endothelium

Lectins which bind sialic acid (aprotinin, wheat germ) were used to measure sialic acid density on the luminal surface of aortic endothelium of rabbit. The bound fluorescein-labelled lectin was released from the sialic acids by the competing ligand N-acetyl-D-glucosamine and measured fluorimetrically. The specificity of the technique was shown by an 80% decrease of bound fluorescence after neuraminidase treatment of the endothelium. Endothelial sialic acid density was the same in the thoracic and abdominal parts of the aorta but significantly less in the arch. Around the orifices of the branches of the intercostal arteries, less surface fluorescence was observed. Ultrastructural studies have shown much less staining of the surface membranes with peroxidase-conjugated wheat germ lectin at these places than elsewhere. These areas, where less sialic acid density was found, coincide with the sites where the atherosclerotic process is known to develop.

Lipid peroxidation and experimental disseminated intravascular coagulation in rats induced by endotoxin

The experimental model of disseminated intravascular coagulation (DIC) in rats induced by a 4 hr sustained infusion of 100 mg/kg endotoxin was used to study the relationship between lipid peroxidation and DIC. Serum thiobarbituric acid (TBA) reactive substances, important and damaging products of lipid peroxidation, increased gradually during the infusion of endotoxin. The levels of TBA reactants in serum, abdominal aortic wall and ileum mucosa were significantly increased in rats infused with 100 mg/kg of endotoxin for 4 hr, as compared with the control rats continuously given 11.4 ml of physiological saline for 4 hr. However, the levels in liver and kidney tissues, and in gastric, jejunum and colon mucosa did not increase significantly.

Increased Ca2+ in the sarcoplasm of aortic smooth muscle cells from rats made hypertensive with DOC. A quantitative ultrastructural and cytochemical study

Uninephrectomized rats were made hypertensive by subcutaneous implantation of pellets of deoxycorticosterone (DOC) and intake of 1% NaCl as drinking solution. Smooth muscle cells from the media of the abdominal aorta of the hypertensive animals and of normotensive rats were studied after fixation in osmium tetroxide containing a calcium precipitating agent (potassium pyroantimonate), a cytochemical method that identifies calcium ions. Specificity of the reaction product was demonstrated by examining samples of the same tissue fixed by a similar solution containing a calcium chelating agent (EGTA). Calcium precipitates were especially numerous in the area of sarcoplasm bordering the nucleus of muscle cells in both groups; in filament rich areas, precipitates were also frequently seen, usually distributed in a linear pattern oriented in the direction of the filaments. Electron opaque reaction product in hypertensive and normotensive rats was quantitated by stereological techniques. Smooth muscle cells from hypertensive animals showed a significant increase in calcium ions within the sarcoplasm (volume density = 0.037 +/- 0.001 SEM) when compared with normotensive controls (volume density = 0.028 +/- 0.002 SEM) (p less than 0.02). The increase in calcium ion in vascular myocytes of hypertensive rats suggest at least in part that intrasarcoplasmic calcium is involved in the pathogenesis of increased arterial tone observed in hypertension.

Medial elastin in the thoracic and abdominal aorta of sheep and lambs

Aortas were removed from six mature lambs and four sheep and pressure fixed at 100 and 120 mmHg pressure (1 mmHg = 133.322 Pa), respectively, in 10% buffered formalin. The numbers of elastin layers were counted from cross sections at different distances down the aorta, from the distal arch to the iliac bifurcation, and showed a linear decrease in the thoracic aorta. In the abdominal aorta there was no difference in values from the diaphragm to the aortoiliac bifurcation in the lamb, but a slight decrease in the sheep. If y = mx + b, where y is the number of medial lamellar units (MLU), b the intercept, x the distance from the last brachiocephalic branch in centimetres, and m the slope, we obtained the following equations (with standard deviations): lamb thoracic aorta; y = -6.29 (+/- 0.71)x + 106 (+/- 12); sheep thoracic aorta; y = -3.46 (+/- 0.40)x + 140 (+/- 21.4); lamb abdominal aorta; y = 0.51 (+/- 1.48)x + 37 (+/- 7.7); sheep abdominal aorta; y = -0.85 (+/- 0.28)x + 66 (+/- 5.9). Tension per lamellar unit was calculated and plotted versus distance yielding a linear increase in the entire lamb aorta but an abrupt increase between thoracic and abdominal aortas in the sheep. This causes the pulse wave to move uniformly with increasing speed along the length of the lamb aorta but would cause an abrupt change in the wave at or about the diaphragm in the sheep. Distortions in the pulse wave could produce local stress concentrations in the abdominal aorta which might render it more susceptible to atherosclerosis than the thoracic aorta.

Experimental atherosclerosis in hypercholesterolemic mini-pigs. Regression of cholesterol ester accumulation in aorta and coronary arteries after treatment with clofibrate, beta-pyridylcarbinol or a normo-lipidemic diet

Studies have been performed on groups of mini-pigs 21-23 months of age, which after 18 months of hypercholesterolemia (approximately 10 mmol) had developed raised atherosclerotic lesions with high levels of cholesterol esters, especially in the abdominal aorta and the coronary arteries. If the hypercholesterolemia was continued for 18 months, no significant change in the cholesterol ester content in the aorta occurred; in the coronary arteries there was a significant decrease in these older pigs. If the hypercholesterolemic pigs also were treated with beta-pyridylcarbinol the findings were very similar to the first. When hypercholesterolemic pigs were treated with clofibrate, or when the hypercholesterolemic diet was replaced with the basal food for 18 months, the plasma cholesterol level was normalized (approximately 2 mmol) within 1-2 months. The cholesterol ester content in the thoracic aorta was reduced in both groups but not that in the abdominal aorta. Clofibrate decreased the cholesterol ester level in the coronary arteries when compared to the hypercholesterolemic group; the drug also reduced the free cholesterol level when compared to the basal group. We suggest that an increased plasma cholesterol level initiated the development of the atherosclerotic lesions; their later development was only partly dependent on the plasma cholesterol level.

Use of 3H-cholesteryl linoleyl ether for the quantitation of plasma cholesteryl ester influx into the aortic wall in hypercholesterolemic rabbits

In this study use was made of 3H-cholesteryl linoleyl ether CLE), a nondegradable analogue of cholesteryl ester (CE) to measure plasma lipoprotein CE influx into rabbit aorta. Autologous serum labeled with 3H-CLE was injected into seven hypercholesterolemic rabbits, and more than 90% of the label was recovered in the plasma compartment 10 minutes after injection. Between 4 hours and 3 days the label was cleared from the circulation with a t1/2 of about 24 hours. Between 4 and 24 hours the lipoproteins isolated at d less than 1.006, d less than 1.019, and d less than 1.063 approached similar specific activity, assuming that 3H-CLE had mixed with the lipoprotein CE pool. The rabbits were killed 7 to 14 days after injection when plasma radioactivity decreased to less than 0.03% of injected dose/ml. Total recovery of the CLE ranged from 70% to 95% and 48% to 72% were found in the liver. The minimum influx of plasma CE into the aortic intima was determined by dividing the label found in the artery by the mean specific activity of the labeled compound in the plasma. The minimum influx into regions with atheromatous involvement ranged from 0.8 to 3.4 micrograms CE/cm2/hr. The rate of influx was highly correlated with the amount of CE mass in the intima and media indicating that the bulk of aortic CE is derived from plasma lipoprotein CE. The method described might be useful in distinguishing between possible effects of "antiatherogenic" drugs on plasma CE influx into the aortic wall from an effect on intracellular CE hydrolysis and subsequent efflux of free cholesterol from the artery.

Additive statistical effects of cadmium and lead on heart-related disease in a North Carolina autopsy series

The association of heart-related mortality with tissue cadmium and lead in a study of autopsies performed on persons who resided in a soft-water, leached-soil area of North Carolina was examined. Liver cadmium concentrations and aortic lead level were indices of these elements. Both cadmium and lead levels had statistically significant correlations with cause of death (heart-related disease vs. non-heart-related disease, excluding cancer). Although cause of death was significantly associated with age, the association with cadmium and lead persisted after statistical adjustment for the effect of age. The combined effects of cadmium and lead provided sufficient information in an additive model to predict cause of death correctly for 80% of the cases, with age contributing insignificantly. These findings indicate the intimate relation of these two trace metals with increased risk of heart-related mortality, even in light of known conventional causes of such deaths.

The expression of results of lipid determinations in arterial tissues: mass per unit weight vs mass per unit area

The interrelations among four methods of expressing the results of lipid determinations in the intima of the abdominal aorta were examined using rank order and product moment correlation methods. The rank order correlations among the four methods were all uniformly high (0.90 or better), indicating that the method of expressing results of lipid analyses is not important when ranking by amount of lipid is the object. The product moment correlations showed a pattern of strong association when the methods paired are expressions of either "content" (mg lipid per 1/2 abdominal aorta vs mg lipid per unit area of aorta, r = 0.980) or "concentration" (mg lipid per dry weight of tissue vs mg lipid per dry defatted weight of tissue, r = 0.980). Correlations of paired methods that express "content" and "concentration" were lower and share only about 50% of common variability. This result can be interpreted as evidence that it is worthwhile to consider reporting chemical findings in reference to units of intimal (or artery) area as well as to unit of weight. If both methods are used some of the problems in interpreting chemical findings in the arterial wall may be clarified.

Isolation and preliminary characterization of proteoglycans dissociatively extracted from human aorta

Aortic proteoglycans (PG) were isolated from human aorta intima-media preparations with 4 M guanidine hydrochloride in the presence of protease inhibitors. The extracted PG mixture comprised 67% of the total aortic PG and was composed of 65% chondroitin sulfate, 22% dermatan sulfate, 8% heparan sulfate, and 4% hyaluronate. Attempts at isolation and purification of PG monomers using isopycnic CsCl gradient centrifugation under associative and dissociative conditions resulted in appreciable loss of PG through associations with co-extracted aortic proteins. The addition of a gel chromatographic step on Sepharose CL-4B under dissociative conditions resulted in separation of PG from the majority of co-extracted proteins. In addition, the procedure resulted in a separation of the PG into a population (PG-I) eluting near the column V0 and one (PG-II) included with a Kav of 0.38. Hyaluronic acid co-eluted with PG-I. The major glycosaminoglycan in PG-I was chondroitin sulfate, (85 to 95%). No dermatan sulfate was detected in PG-I, but this glycosaminoglycan was the predominant glycosaminoglycan in PG-II (50 to 70%). Heparan sulfate was present in small amounts in both PG-I and PG-II. Data presented support the proposal of at least three species of PG monomers in the aortic wall. Chromatographic studies under dissociative and associative conditions indicated that PG comprising PG-I but not PG-II were capable of associations with hyaluronic acid.

Evans blue dye. Accumulation in swine aortic intimal cell collections and atherosclerotic lesions

A two-part study concerned the accumulation of intravenously injected Evans blue dye in the abdominal aorta of swine. In normolipidemic swine weighing up to 90 kg each, Evans blue accumulated predominantly in areas of the aorta that were the site of intimal smooth muscle cell collections. The second part of the study dealt with Evans blue accumulation in swine with advanced atherosclerosis. The extent of blue staining in these animals was not significantly different than in normolipidemic, nonatherosclerotic swine of the same size. The dye showed a predilection for raised atherosclerotic lesions, but only one quarter of the surface of these lesions was stained. Histologic studies of the uppermost portion of blue and nonblue lesion areas showed that the dye preferentially accumulated in regions with lower concentrations of foam cells. Injected isotopic cholesterol tended to accumulate in the blue rather than the nonblue areas.

Possible relationship of cholesterol accumulation and collagen synthesis in rabbit aortic tissues

Male adult New Zealand rabbits were fed a 2% cholesterol diet for 60 days followed by 10, 20, or 30 days of normal low cholesterol diet. Collagen synthesis was estimated by measuring aortic prolyl hydroxylase activity. Tissue cholesterol accumulation rates were estimated by dividing total tissue cholesterol by the number of experimental days. It was found there was a high degree of correlation between aortic collagen synthetic activity and the rate of aortic cholesterol accumulation. These data were interpreted as suggesting that increased collagen synthesis may be associated with the accumulation and/or retention of increased aortic cholesterol.

Copper salts for growth stimulation and alleviation of aortic rupture losses in turkeys

Approximately 4000 Large White, day-old turkey poults were used in a series of eight experiments to study the effects of dietary copper supplementation. The hens were grown to 15 or 16 weeks and toms to 24 weeks of age. Either copper as the oxide or sulfate (hydrate) at 120 ppm stimulated growth up to 10% with a concurrent reduction in feed requirement. Levels of 60 ppm were not adequate, whereas 240 ppm were not toxic. There was a greater response to copper in the presence of 4-nitrophenylarsonic acid (4-nitro) or with low protein diets. In two of the eight studies copper enhanced aortic elastin content. Incidence of aortic rupture was greater in the presence of 4-nitro and was reduced by one-half through copper supplementation. Liver copper was not altered by 60 or 120 ppm Cu; 240 ppm caused a significant increase.

The plasminogen activator of the arterial wall

The plasminogen activator in 645 specimens of various human arteries--thoracic, abdominal aorta, carotic, pulmonary, renal, basilar, coronary - was studied using Todd's histochemical method. 92 cadavers were used, 1--18 hours post mortem from subjects aged from 272 days to 83 years. 45 specimens of pulmonary, renal and splenic arteries were obtained during surgery. The greatest fibrinolytic activity was within the adventitia. Intima occasionally showed very little fibrinolytic activity, or none at all. No statistically significant differences in plasminogen activator activity were found between the various arteries examined. A statistically significant increase in fibrinolysis in adventitia of atherosclerotic arteries was established. No correlation was found between the fibrinolytic activity of the arteries and their alkaline phosphatase content. Some properties of the plasminogen activator of the arterial vessel wall were evaluated. Influence of storage, inactivation with epsilonaminocaproic acid and extracted with potassium thiocyanate was studied.

Abnormal ion and water composition of veins and normotensive arteries in coarctation hypertension in rats

We examined the water, sodium, and potassium composition of the thoracic aorta, abdominal aorta (plus iliac arteries), and veins (vena cava and portal vein) from rats with aortic coarctation. The aortas of 10 rats (group A) were coarcted above the renal arteries to produce hypertension. Control groups consisted of 10 rats sham-coarcted above and 10 rats coarcted below the renal arteries. In group A rats heart weights and carotid artery pressures were elevated over controls (P less than 0.01), whereas there were no significant differences in femoral arterial pressures. In group A rats both the hypertensive thoracic aorta and the normotensive abdominal aorta contained about 20% more water per unit of wet weight, and about 35% and 60% more sodium and potassium, respectively, per unit of dry weight than did the corresponding portions of aorta from control rats (P less than 0.01). In group A rats water (P less than 0.01), sodium (P less than 0.02), and potassium (P less than 0.05) contents of veins also were increased. There were no significant correlations between level of carotid arterial pressure and magnitude of changes in arterial and venous composition, nor were there significant differences between the magnitude of changes in the normotensive and hypertensive portions of the aorta. These results indicate that in rats abnormalities in vascular wall salt and water content are not necessarily a direct effect of the elevated pressure in hypertension.

Renin secretion at the individual nephron level

Blood was collected from the descending aorta, from a renal efferent arteriole and from the renal vein of a rat. The renin concentrations of the blood samples were measured. The renal vein renin concentration was 673 +/- 81 (SE) ng ml-1h-1 which was significantly higher than the concentration in the aorta of 456 +/- 50 (SE) ng ml-1h-1. The concentration of renin in the renal efferent arteriole was significantly lower than that in the aorta. These observations imply that net renin secretion is a combination of two processes; removal between artery and efferent arteriole and entry between efferent arteriole and renal vein. It appears that renin is released into the interstitium and enters the circulation at the capillary level rather than being released into the afferent or efferent arterioles. This mode of secretion supports the suggestion that the renin angiotensin system may primarily work intra-renally rather than through the systemic circulation.

Oxygen tensions in healing anastomosis of rabbit aorta

Tissue oxygen tensions in healing anastomoses of rabbit abdominal aortas were measured with ultramicro-oxygen cathodes with 1 to 3 mum tips. Two days after constructing the anastomosis, the over-all profile of intramural oxygen tension was different markedly from that of normal aortic wall, showing a progressive fall of Po2 from adventitia to media and no increasing gradient from media to intima. One week after operation to intimal Po2 increased and the oxygen gradient due to diffusion from the lumen was re-established. By the end of the second week adventitial and medial oxygen tensions reached their minimum. Six weeks after operation the oxygen tensions in the anastomosis resembled those of an intact aortic wall, suggesting that the availability of oxygen to the injured area had been re-established fully.

Lipid profile in the evolution of experimental atherosclerotic plaques from thrombus

Nonocclusive white mural thrombosis was induced in the abdominal aortae of normolipidemic rabbits by insertion of a polyethylene catheter into the abdominal aortae. The thrombus subsequently organized into intimal thickenings which resembled fibrofatty type atherosclerosis seen in man, showing large numbers of foam cells containing stainable lipid, fatty necrotic centers, cholesterol clefts, calcification, and fibrous caps. The lipid composition of the thrombus and lesions was followed at serial time intervals from 4 hours to 60 weeks. Lipid analysis showed significant concentrations of lipid in the early lesions and with time these lipid concentrations increased and later decreased. These studies demonstrate that the fibrofatty lesions derived from a white thrombus have significant amounts of the same lipids that characterize the atherosclerotic lesions of man, however, there is a lower proportion of cholesterol to the other constituents and a higher proportion of phospholipids. The free cholesterol and cholesteryl ester of the 4-day lesions were much greater than that of platelets alone indicating that significant amounts of plasma are trapped in a thrombus when it forms.

Chemical composition of the rabbit aorta during development

Changes in both the relative and the absolute amounts of collagen and elastin in segments of the aortic wall of New Zealand white rabbits (1-130 weeks old) were determined by chemical analysis. As in other mammals, elastin was the major component of the wall of the thoracic aorta although the proportion of collagen increased along the abdominal aorta and into the more distant arteries. Data on the absolute amounts of collagen and elastin per aorta showed that collagen and elastin deposition was most rapid during the early postnatal weeks. Although this deposition slowed in later weeks, it continued in both segments of the aorta throughout the period of this study. The proportion of the wall mass attributable to collagen and to elastin increased very rapidly during the first postnatal weeks and then, after 20 weeks, declined. The results of the present study indicate that there is a significant increase in some unidentified nonscleroprotein component within the aortic wall of older rabbits.

Action of growth hormone and thyroxine on aortas of hypophysectomized dogs

Young dogs were surgically hypophysectomized and maintained for eleven weeks postoperatively with age-matched normal controls. For three weeks prior to sacrifice, four hypophysectomized dogs were given daily injections of bovine growth hormone (GH, 0.2 mg./kg.) and another four were given daily injections of thyroxine (T4, 5 μg./ kg.). Aortas were removed, cleaned of adventitia and divided into three segments: arch, thoracic and abdominal. Each portion was analyzed for collagen, elastin, deoxyribonucleic acid (DNA), calcium, total mucopolysaccharides (MPS), hyaluronic acid (HA), heparan sulfate (HS), dermatan sulfate (DS) and chondroitin sulfate (GS). The arch and thoracic aortas of normal animals were found to contain more DNA, CS and elastin but less collagen than the abdominal aorta. Removal of the hypophysis resulted in an overall increase in elastin and DNA content and caused a decrease in all sulfated MPS. Administration of either CH or T4 to hypophysectomized dogs had a profound effect on the majority of constituents in all segments of aorta. GH returned the content of elastin, DS and CS toward normal in at least two of the three aortic segments. T4 returned the content of DNA, DS and CS toward normal in all segments. Moreover, T4 treatment caused significant reductions in collagen and HA contents of thoracic and abdominal segments. These results indicate that: (1) the composition of normal aorta varies with the segment studied; (2) the composition of the aorta is markedly affected by hypophysectomy, CH and T4 treatment; and (3) individual aortic segments show differential sensitivity to a given hormone.