No abstract

The purpose of this research was to study the effect of pressure on arterial hydration in vitro and the effect of pressure and flow (stirred reagent) on the in vitro transport of 125I-albumin and 125I-LDL into deendothelialized minipig aortas over a 24-hour period. It was found that the arterial hydration (fractional mass of water) was 0.740 +/- 0.0043 SEM for control tissue; after 24 hours this rose to 0.745 +/- 0.0038 for 0 mm Hg, 0.752 +/- 0.0046 for 100 mm Hg, and 0.755 +/- 0.0065 for 200 mm Hg. In the transport studies, the following effects were found. The reagent radioactivity concentration and composition did not change with pressure or stirring over the 24-hour period. For unpressurized tissue, the 24-hour normalized uptake [uptake (M mg cm-2) divided by reagent concentration (co mg cm-3)] of albumin was (4.86 +/- 0.43 cm) X 10(-3) from stirred and (5.46 +/- 0.36 cm) X 10(-3) from nonstirred reagent; that of LDL was (0.31 +/- 0.02 cm) X 10(-3) from stirred and (0.37 +/- 0.02 cm) X 10(-3) from nonstirred reagent. Pressurization (100 mm Hg) of the tissue increased albumin uptake by 52% from stirred and by 125% from nonstirred reagent and the LDL uptake by 52% from stirred and 241% from nonstirred reagent. Pressure increased the intimal surface concentration of albumin and LDL at the nonstirred, but not at stirred, interfaces. The electrophoretic properties of the intimal surface fluid showed only minor differences from those of the bulk reagent. These data demonstrate that pressure causes a slight, but significant, increase in arterial hydration and that radiolabeled albumin and LDL appear to be sieved by the superficial intimal layers of the deendothelialized porcine aorta under the in vitro conditions of this study.

The effects on porcine arterial structure and permeability of a 4-hour in vitro incubation at 37°C in eight different blood-derived and synthetic nutrient media were examined. Changes in arterial permeability were inferred from the normalized, 1-hour, pressurized, transendothelial uptake (M/c t cm) of porcine l25 I-albumin in 60 porcine aortic tissue preparations using an organ-support system. The organ-support system provided experimental control of ambient gas composition, temperature, transmural pressure, flow (stirring), and nutrient media at a number of sites along the vessel. Light and electron microscopic (scanning and transmission) structural correlations with the observed permeability changes were examined. The M/c 0 from the autogenous serum (AS) medium was used as the "control" measurement in each vessel preparation. (Grand mean M/c 0 for AS from all studies was 0J12±0.011 [xlO~3] [mean±SEM] cm, n=60.) For brevity, M/c 0 values from the other media are expressed below as a percentage of the corresponding paired Af/c, from the AS. Uptake from heparinized autogenous blood was 113±9% of that from AS (p=0.119); from heparinized autogenous plasma was 135± 10% (p=0.048); from AS+heparin was 97±5% (p=0.498); from pooled porcine serum was 113±9% (p=0.037); from a synthetic medium was 131 ±8% (p=0.004); and from a physiological hetastarch solution was 532±8% (p=0.0002). Associated light microscopic structural changes and ultrastructural changes were not found. We conclude that 1) incubation with AS and heparinized blood (both of which are autogenous blood substances containing platelet products or platelets) provided the best support for the endothelial barrier function, whereas heparin plasma, pooled serum, a synthetic medium, and particularly hetastarch provided poorer support; 2) arterial permeability can increase significantly without discernible endothelial ultrastructural changes; and 3) AS and to a lesser extent heparin blood should provide a suitable nutrient medium for short-term (<4-hour) metabolic support of the endothelial surface and subjacent tissues. A understanding of the essential factors required for optimum metabolic support of excised blood vessels in vitro is of considerable interest in many areas of vascular biology. In studies of basic vascular biology, the development of an appropriate, metabolically supported, in vitro arterial preparation would provide an important experimental bridge between tissue-culture methodology and in vivo experimentation. For example, unlike those in a tissue-culture system, the cells in such an organ-support system (OSS) would continue to communicate with their normal matrix milieu and cellular cohorts. Unlike the in vivo state,

The location and progression of changes in arterial permeability and structure were studied in nine dogs over a 13-week period following left coronary catheterization with standard coronary catheters. Changes in arterial permeability were analyzed by quantitating Evans blue dye (EBD) uptake over the aortic luminal surface (blue areas). Structural changes were assessed by light and electron microscopy. In the catheterized animals, compared to uncatheterized controls, we observed a significant increase in aortic luminal EBD uptake that was maximal 4 hours after the procedure but still present up to 13 weeks later. Microscopic analysis of "blue areas" shortly after the procedure revealed widespread endothelial denudation, platelet and leukocyte adherence, with occasional intimal avulsions, disruption of the internal elastica, and thrombi. The EBD uptake patterns in association with the electron microscopic findings in these animals suggested that 67-89% of the aortic endothelium was removed by the catheter during the procedure. The proliferative response that occurred following this catheter-induced injury produced fibrocellular intimal thickening in the aortas and left main coronary arteries of animals studied 10 to 92 days after the procedure. In the aortic root, such thickening was associated with incomplete re-endothelialization, thrombogenicity, and grossly abnormal permeability patterns. We conclude that significant catheter-induced intimal injury can occur during coronary angiography. In the canine model, such injury is associated with widespread fibrocellular intimal thickening and abnormal permeability that persists for at least 13 weeks after the procedure.

The purpose of this study was to characterize the nucleotide profiles of a normal porcine elastic and muscular artery. Tissue samples (50 to 150 mg) were excised from the descending thoracic aorta and from the femoral artery of 14 normocholesterolemlc, anesthetized mlnlplgs. In three animals, transmural myocardlal samples were also obtained. Nucleotide and nucleoslde concentrations were analyzed by using a recently developed ion-palrlng, reverse-phase, high-performance liquid chromatographlc method. The arterial samples contained relatively low concentrations of adenoslne triphosphate, approximately one-eighth that of the myocardlal counterpart. Relative to the femoral artery, the aortic samples had significantly lower adenylate energy charges and higher levels of adenoslne dlphosphate, adenosine monophosphate, adenoslne, and inoslne. These baseline aortic levels did not change after In vitro exposure to 95% oxygen. The different energy states observed In the two arteries may reflect functional or metabolic differences in their medial smooth muscle cell populations. Alternatively, the lower energy state observed in the thicker walled aorta may be a manifestation of Inadequate medial oxygen delivery that persists despite oxygen enrichment In vitro. We conclude that arterial energy states exhibit regional variation. This Information will serve as a point of departure for the Investigation of the role energy states may play In the atherosclerotic process. (Arteriosclerosis 10:745-750, September/October 1990) E nergy-requiring processes in the arterial wall, as in all tissues, require adequate levels of high-energy compounds, generally adenosine triphosphate (ATP). A significant proportion of the required high energy compounds is generated by the oxidative catabolism of various substrates.1 •^ Since oxygen is required for such reactions, the ability to maintain adequate levels of high-energy compounds would appear to depend on oxygen delivery to the metabolizing arterial cells, of which the medial smooth muscle cells are quantitatively most important. Studies done in rabbits have suggested that oxygen delivery in many arteries is insufficient to maintain an aerobic environment in the mid-media] regions. 45 It is plausible that such tissue hypoxia may be associated with alterations of highenergy phosphates and their metabolites. The purpose of this study was to characterize the nucleotide and nuclecside profiles of a normal porcine muscular artery (femoral artery) and elastic artery (descending thoracic aorta) to assess whether such profiles suggest the presence of medial hypoxia and to assess whether such profiles vary in these two types of arteries. Methods Experimental AnimalsFourteen 2-to 3-year-old normocholesterolemic minipigs (Sinclair Research Farm, Columbia, MO) with an average weight of 75 kg were used in this study. All procedures were approved by the Institutional Laboratory Animal Care and Use Committee at the Ohio State University. The animals were anesthetized with ketamine (40 mg/kg) plus acepromazi...