Normal Rat Aorta Research Articles

Viscoelastic properties of the aorta of hypertensive rats.

SummaryThe viscoelastic properties of strips of aorta from normal and hypertensive rats have been determined. The aortas of hypertensive animals are stiffer and more viscous than those of normal rats. The pari passu increase in stiffness and viscosity is evidence that muscle is the chief structural component resulting in increased stiffness. Photomicrographs of the aorta of normal and hypertensive rats support this idea.

Utilization of glucose, octanoate and palmitate by normal rat aorta, and the effect of these acids and of albumin on glucose metabolism.

SummaryInfluence of octanoate and palmitate on the uilization of glucose by rat aortic tissue was examined. Octanoate but not palmitate depressed the oxidation of glucose-U-14C to CO2. No effect was exerted by these fatty acids on glucose uptake, conversion of glucose to lipids, or oxygen uptake. Commercial bovine serum albumin, used as a carrier for these acids, depressed glucose uptake, increased CO2 production from radioactive glucose, and increased oxygen uptake. These effects were abolished with purification of albumin by dialysis and charcoal treatment. The purified albumin did, however, decrease incorporation of glucose radioactivity into tissue lipid. In a short-term experiment (18-min incubation) octanoate was oxidized to water-soluble products and CO2 much more rapidly than was palmitate. These results suggest that oxidation of free fatty acid, at the more rapid rate observed with octanoate, has a sparing effect on the oxidation of glucose to CO2 in aortic tissue.

Changes in phospholipase a, lipase and cholesterol esterase activity in the aorta in experimental atherosclerosis in the rabbit and rat

Summary Esterase activity has been examined in the aorta of rats given hyperchol-esterolaemic, thrombogenic or atherogenic diets, and rabbits given an atherogenic, semi-synthetic diet low in cholesterol. In normal rat aorta, the specific activity values are in the numerical order of phospholipase A > lipase > cholesterol esterase. In the rabbit the activities were in the same order but of much lower magnitude. In the rat, feeding an atherogenic diet containing 40 % peanut oil, 5 % cholesterol and 2 % cholic acid produced an increased phospholipase A and lipase, and a decreased cholesterol esterase activity compared with normal animals. Replacement of peanut oil with butter produced no change in phospholipase A and cholesterol esterase and only a small increase in lipase. Thiouracil depressed the higher lipase and abolished the increased phospholipase A activity of the peanut oil group, and decreased cholesterol esterase in both the butter and peanut oil groups. In rabbits given the semi-synthetic low cholesterol diet for 10 and 32 weeks, a decrease in phospholipase A and cholesterol esterase activity was seen compared with normal animals. An increased lipase activity was seen at 10 weeks but not at 32 weeks. It is concluded that the high lipase and low cholesterol esterase activity in the peanut oil fed rat, and the low cholesterol esterase activity in the semi-synthetic diet fed rabbit may be contributing factors in the dietary production of atherosclerosis in these two species.

The effect of β,β′-iminodipropionitrile treatment and alloxan diabetes on the glycosaminoglycans of the rat retina and aorta

1. 1. The glycosaminoglycans from normal and alloxan-diabetic rat aorta and retina, with and without prior incubation with 35SO 4 2−, the glycosaminoglycans of β,β′-iminodipropionitrile-treated rat aorta and retina and the glycosaminoglycans from isolated human and bovine retinal vascular systems have been quantitatively separated by chromatography on cetylpyridinium chloride/cellulose columns. 2. 2. Significant increases in the chondroitin sulphate content of both tissues were observed in alloxan diabetes, based on hexosamine determinations and 35SO 4 2− uptake. 3. 3. A significant increase in the ‘neutral’ fraction was observed in the retina, but not in the aorta, after β,β′-iminodipropionitrile treatment. 4. 4. The neutral fraction constituted 83 and 86% of the total hexosamine of isolated human and bovine retinal microvascular systems compared with 60% in the rat aorta.

Movement of labeled cholesterol between plasma lipoprotein and normal arterial wall across the intimal surface.

Normal rat aortas were incubated with their intimal surfaces in contact with a lipoprotein solution containing isotopically labeled free cholesterol. Uptake of cholesterol by the tissue increased with increasing concentration toward a plateau level. Maximum uptake of free cholesterol was estimated to be 13 µg/cm 2 per 24 hours, and uptake at physiological cholesterol concentration was 7.9 µg/cm 2 per 24 hours. Aortas containing labeled cholesterol were prepared by intragastric administration of cholesterol-7α- 3 H to normal rats. Experiments in vitro with these aortas demonstrated that efflux across the intimal surface was dependent upon presence of lipoprotein in the medium. This efflux was not retarded by prior boiling of the tissue. These results support suggestions that movement of labeled free cholesterol from plasma into the arterial wall may be largely the result of a physicochemical exchange between lipoprotein and endothelium.

Changes in cellularity of the normal rat aorta during maturation

DNA content of aortas from rats of various ages and weights was determined colorimetrically. Total DNA content increases progressively with aortic growth, while DNA concentration decreases. This presumably reflects decreasing cellularity with maturation which may account for diminished metabolic rates of some biochemical processes. La teneur en DNA des aortas de rats d'âges et de poids différents a été dosee par colorimétrie. Le DNA total augmente progressivement avec la croissance de l'aorte, tandis que la concentration de DNA diminue. Ceci traduit probablement la différenciation cellulaire diminuée lors de la maturation, ce qui expliquerait la diminution des taux métaboliques de quelques processes biochimiques. Der DNA-Gehalt in Aorten von Ratten verschiedenen Alters and Gewichtes wurde kolorimetrisch bestimmt. Der Gesamt-DNA-Gehalt vermehrte progressiv mit dem Wachstum der Aorta, während die DNA-Konzentration verminderte. Dieser Befund deutet wahrscheinlich auf eine Verringerung der Zelldifferenzierung während der Reifung, die auch verantwortlich sein wird für die niedrigeren Stoffwechselraten einer Anzahl biochemischer Prozesse.

Cholesterol kinetics in the normal rat aorta, and the influence of different types of dietary fat

Summary Groups of rats, maintained on cholesterol-free diets containing either 30 % safflower oil or 30 % coconut oil, were given single intragastric doses of (4-14C) -cholesterol. The ensuing rise in radioactivity of aorta cholesterol was substantially higher in the coconut-oil group than in the safflower-oil group. The two groups were nearly identical in regard to plasma-cholesterol concentrations, plasma-cholesterol specific activitytime curves, aorta-cholesterol concentrations, and in vitro synthesis of cholesterol from acetate by the aorta. It was therefore concluded that coconut-oil feeding had resulted in faster transfer of cholesterol from plasma into the wall of the aorta, in comparison with safflower-oil feeding, under conditions of identical plasma-cholesterol concentrations. It was estimated that transfer from plasma accounted for roughly 3/4 of the cholesterol in the wall of the aorta in the safflower-oil group. The data did not permit an estimate of this parameter in the animals on coconut oil. Analysis of the fatty-acid constituents of plasma cholesterol esters and triglycerides revealed a distinct tendency in the direction of the composition of dietary fat. Plasma phosphatide fatty acids were influenced only slightly by diet.

Electron microscope study of the normal rat aorta.

The fine structure of the normal rat aorta is described. The presence of a sub-endothelial layer, the oblique orientation of the smooth muscle cells with respect to the aortic axis, and the occurrence of desmosomes between these cells and adjacent elastic laminae, are emphasized. Lead-stained collagen presented a characteristic signet-ring appearance on cross-section. The rats examined were the pair-fed controls for the lathyritic series described in a separate communication.

Oxygen consumption of the thoracic aorta of normal and hypercholesteremic rats.

The respiratory activity of the thoracic aorta wall of hypercholesteremic rats was shown to be 30 to 40 per cent higher than in normal animals. The addition, in vitro, of serum of different cholesterol content did not affect the oxygen consumption.