Morphology and metabolism of an aortic intima-media preparation in which an intact endothelium is preserved

The effect of end-ischaemic normothermic machine perfusion on donor hepatic artery endothelial integrity

BACKGROUND

Ex vivo normothermic machine liver perfusion (NMLP) involves artificial cannulation of vessels and generation of flow pressures. This could lead to shear stress-induced endothelial damage, predisposing to vascular complications, or improved preservation of donor artery quality. This study aims to assess the spatial donor hepatic artery (HA) endothelial quality downstream of the cannulation site after end-ischaemic NMLP.

METHODS

Remnant HA segments from the coeliac trunk up to the gastroduodenal artery branching were obtained after NMLP (n = 15) and after static cold storage (SCS) preservation (n = 15). Specimens were fixed in 10% neutral buffered formalin and sectioned at pre-determined anatomical sites downstream of the coeliac trunk. CD31 immunohistostaining was used to assess endothelial integrity by a 5-point ordinal scale (grade 0: intact endothelial lining, grade 5: complete denudation). Endothelial integrity after SCS was used as a control for the state of the endothelium at commencement of NMP.

RESULTS

In the SCS specimens, regardless of the anatomical site, near complete endothelial denudation was present throughout the HA (median scores 4.5-5). After NMLP, significantly less endothelial loss in the distal HA was present compared to SCS grafts (NMLP vs. SCS: median grade 3 vs. 4.5; p = 0.042). In NMLP specimens, near complete endothelial denudation was present at the cannulation site in all cases (median grade: 5), with significantly less loss of the endothelial lining the further from the cannulation site (proximal vs. distal, median grade 5 vs. 3; p = 0.005).

CONCLUSION

Loss of endothelial lining throughout the HA after SCS and at the cannulation site after NMLP suggests extensive damage related to surgical handling and preservation injury. Gradual improved endothelial lining along more distal sites of the HA after NMLP indicates potential for re-endothelialisation. The regenerative effect of NMLP on artery quality seems to occur to a greater extent further from the cannulation site. Therefore, arterial cannulation for machine perfusion of liver grafts should ideally be as proximal as possible on the coeliac trunk or aortic patch, while the site of anastomosis should preferentially be attempted distal on the common HA.

Effects of factor Xa on the expression of proteins in femoral arteries from type 2 diabetic patients

AIM

Further to its pivotal role in haemostasis, factor Xa (FXa) promotes effects on the vascular wall. The purpose of the study was to evaluate if FXa modifies the expression level of energy metabolism and oxidative stress-related proteins in femoral arteries obtained from type 2 diabetic patients with end-stage vasculopathy.

METHODS

Femoral arteries were obtained from 12 type 2 diabetic patients who underwent leg amputation. Segments from the femoral arteries were incubated in vitro alone and in the presence of 25 nmol l(-1) FXa and 25 nmol l(-1) FXa + 50 nmol l(-1) rivaroxaban.

RESULTS

In the femoral arteries, FXa increased triosephosphate isomerase and glyceraldehyde-3-phosphate dehydrogenase isotype 1 expression but decreased pyruvate dehydrogenase expression. These facts were accompanied by an increased content of acetyl-CoA. Aconitase activity was reduced in FXa-incubated femoral arteries as compared with control. Moreover, FXa increased the protein expression level of oxidative stress-related proteins which was accompanied by an increased malonyldialdehyde arterial content. The FXa inhibitor, rivaroxaban, failed to prevent the reduced expression of pyruvate dehydrogenase induced by FXa but reduced acetyl-CoA content and reverted the decreased aconitase activity observed with FXa alone. Rivaroxaban + FXa but not FXa alone increased the expression level of carnitine palmitoyltransferase I and II, two mitochondrial long chain fatty acid transporters. Rivaroxaban also prevented the increased expression of oxidative stress-related proteins induced by FXa alone.

CONCLUSIONS

In femoral isolated arteries from type 2 diabetic patients with end-stage vasculopathy, FXa promoted disruption of the aerobic mitochondrial metabolism. Rivaroxaban prevented such effects and even seemed to favour long chain fatty acid transport into mitochondria.

Expression of cytoskeleton and energetic metabolism-related proteins at human abdominal aortic aneurysm sites

OBJECTIVE

The purpose of this study was to evaluate the expression of proteins related to cytoskeleton and energetic metabolism at abdominal aortic aneurysm (AAA) sites using proteomics. Several remodeling-related mechanisms have been associated with AAA formation but less is known about the expression of proteins associated with cytoskeleton and energetic metabolism in AAAs.

METHODS

AAA samples (6.73 ± 0.40 cm size) were obtained from 13 patients during elective aneurysm repair. Control abdominal aortic samples were obtained from 12 organ donors. Proteins were analyzed using two-dimensional electrophoresis and mass spectrometry.

RESULTS

The expression of filamin was increased in the AAA site compared to control abdominal aortic samples while microfibril-associated glycoprotein-4 isotype 1, annexin A5 isotype 1, and annexin A2 were reduced compared with control abdominal aortic samples. Reduction in expression level of energetic metabolism-associated proteins such as triosephosphate isomerase, glyceraldehyde 3-phosphate dehydrogenase, and cytosolic aldehyde dehydrogenase was also observed in AAAs compared to controls. Reduction of triosephosphate isomerase expression was also observed by Western blot, which was accompanied by diminished triosephosphate isomerase activity. At the AAA site, pyruvate dehydrogenase expression was reduced and the content of both lactate and pyruvate was increased with respect to controls without changes in lactate dehydrogenase activity.

CONCLUSIONS

The present results suggest that an anaerobic metabolic state may be favored further to reduce the expression of cytoskeleton-related proteins. The better knowledge of molecular mechanism involved in AAAs may favor development of new clinical strategies.

Endothelial- and nitric oxide-dependent effects on oxidative metabolism of intact artery

Oxidative metabolism and its possible modulation by nitric oxide (NO) was examined in endothelial-intact and endothelial-denuded segments of porcine carotid arteries. Endothelial-intact arteries displayed appropriate NO-mediated vasorelaxation to acetylcholine (ACh). Endothelial-denuded arteries demonstrated absent vasorelaxation to ACh stimulation and depressed contractile responsiveness to K(+) depolarization, which was normalized by inhibition of NO synthesis by N(omega)-nitro-L-arginine methylester (L-NAME). Confirmation that carotid arteries continued to produce NO despite removal of the endothelium was indicated by detection of NO metabolites in the incubation medium bathing the arteries. O(2) consumption and the oxidation of glucose and fatty acid were depressed in endothelial-denuded arteries. Depression of O(2) consumption and glucose oxidation was completely reversed by treatment with L-NAME. We conclude that endogenous NO produced by non-endothelial vascular cells depresses contractility, O(2) consumption, and oxidation of energy substrates in vascular smooth muscle. The endothelium may play a role in oxidative metabolism of vascular smooth muscle possibly by modulating the effects of NO produced by other cells of the vessel wall, or by other factors.

Estimating oxygen transport resistance of the microvascular wall

The problem of diffusion of O(2) across the endothelial surface in precapillary vessels and its utilization in the vascular wall remains unresolved. To establish a relationship between precapillary release of O(2) and vascular wall consumption, we estimated the intravascular flux of O(2) on the basis of published in vivo measurements. To interpret the data, we utilized a diffusion model of the vascular wall and computed possible physiological ranges for O(2) consumption. We found that many flux values were not consistent with the diffusion model. We estimated the mitochondrial-based maximum O(2) consumption of the vascular wall (M(mt)) and a possible contribution to O(2) consumption of nitric oxide production by endothelial cells (M(NO)). Many values of O(2) consumption predicted from the diffusion model exceeded M(mt) + M(NO). In contrast, reported values of O(2) consumption for endothelial and smooth muscle cell suspensions and vascular strips in vitro do not exceed M(mt). We conjecture that most of the reported values of intravascular O(2) flux are overestimated, and the likely source is in the experimental estimates of convective O(2) transport at upstream and downstream points of unbranched vascular segments.

Endothelium during microarterial graft procurement and transplantation

Microarterial grafts are prone to mechanical endothelial injury that can have profound effects on the transplanted vessel, a factor neglected in studies on vascular changes post-transplantation. The aim of this study was to document the integrity of the endothelial lining after both procurement and transplantation of rat aortic grafts, using a minimal touch technique with and without the use of topical papaverine. It was found that procurement using a simple minimal touch technique preserved the endothelium and transplantation could be performed without endothelial injury. The appearance of "normal" endothelium varied with the degree of distension of the artery, suggesting a dynamic endothelial architecture to accommodate changes in the surface area of the artery during pulsation. These findings indicate that transplantation of an arterial segment without injury to the intima is possible and stress the importance of technical controls after both procurement and transplantation to prevent the use of injured grafts and misleading results.

Endothelin mediates renal vasodilation and hyperfiltration during pregnancy in chronically instrumented conscious rats

Profound vasodilation of the kidneys and other nonreproductive organs transpires during early pregnancy. Because nitric oxide (NO) was found to mediate renal vasodilation and hyperfiltration in conscious pregnant rats, and endogenous endothelin (ET) was suggested to be vasodilatory in the renal circulation of nonpregnant rats, we tested whether endothelin mediates the NO-dependent changes in the renal circulation during pregnancy. Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured in conscious pregnant and virgin rats before and during infusion of 30 micrograms/min RES-701-1 (a selective ETB receptor subtype antagonist). Baseline GFR and ERPF were significantly increased by 35% in gravid rats relative to virgin controls. During infusion of RES-701-1, the pregnant rats responded more robustly, showing a greater decline in both GFR and ERPF such that renal function converged in the two groups of rats. ERPF also converged in pregnant and virgin rats during infusion of SB-209760, a nonselective ETA/B receptor subtype antagonist. Combined infusion of Nomega-nitro-L-arginine methyl ester [L-NAME, an NO synthase (NOS) inhibitor] and RES-701-1 reduced GFR and ERPF to levels comparable to those reached with either agent given alone, suggesting inhibition of a common vasodilatory pathway. RES-701-1 and SB-209670 significantly lowered the cGMP content of small renal arteries from gravid and virgin rats in vitro, strengthening the link between the renal endothelial ETB receptor subtype and NO. Importantly, we showed that RES-701-1 is not a direct inhibitor of NOS. We conclude that endothelin mediates the NO-dependent changes in the renal circulation of conscious rats during pregnancy.

Effect of palmitate on carbohydrate utilization and Na/K-ATPase activity in aortic vascular smooth muscle from diabetic rats

Several investigators have reported that carbohydrate metabolism is suppressed in blood vessels from diabetic (Db) rats. However, it is not known if metabolites from the reciprocal increase in oxidation of long-chain fatty acids that accompanies insulin-deficiency exacerbates the suppression of this pathway in the Db blood vessels. Such inhibition may have particularly deleterious consequences in vascular smooth muscle since aerobic glycolysis is believed to preferentially fuel the sarcolemmal Na/K ATPase in this tissue. Therefore, this study evaluated the effect of physiological (0.4 mM) and elevated (1.2 mM) concentrations of the long-chain fatty acid palmitate on both carbohydrate utilization and Na/K-ATPase activity in aorta from insulin-deficient Db rat. Thoracic aorta were removed from 10 week Db (streptozotocin 60 mg/Kg , i.v.) or control (C) rats and intima-media aortic preparations were incubated in the absence or presence of palmitate. Glycolysis (microM/g dry wt/h) and glucose oxidation (microM/g dry wt/h) were quantified using 3H-glucose and 14C-glucose, respectively. Na/K-ATPase activity was estimated by the measurement of 86rubidium uptake in the absence and presence of 2 mM ouabain. In the absence of exogenous palmitate, glycolysis (p < 0.05), glucose oxidation (p < 0.01) and the estimated ATP production from exogenous glucose were decreased in aorta from Db rat. However, despite this diminished rate of glycolysis, Na/K ATPase activity was similar in Db and C aorta. Palmitate (0.4 mM) inhibited Na/K ATPase activity and glucose oxidation to a similar extent in both Db and C but had no effect on glycolysis in either group. Elevation of palmitate to 1.2 mM had no additional inhibitory effect on glucose oxidation, Na/K ATPase activity or glycolysis in either the Db or C aorta. The metabolism of exogenous palmitate restored the ATP production in Db to control values. These data demonstrate that, despite the diminished glycolysis and glucose oxidation demonstrated in the Db tissue, Na/K ATPase activity was comparable in the C and Db aorta, in the absence or presence of exogenous long-chain fatty acid. Therefore, the accelerated oxidation of palmitate in diabetic vascular smooth muscle had no additional inhibitory effect on glycolysis or Na/K ATPase activity. These data suggest that Na/K ATPase activity in vascular smooth muscle is not impaired by the altered pattern of substrate utilization that occurs in insulin-deficient Db rats.

Biaxial mechanical properties of carotid arteries from normotensive and hypertensive rats

Hypertension is known to decrease arterial distensibility and volumetric compliance, as reported from pressure-volume experiments and ring and strip studies of human and animal large arteries. However, recent data using noninvasive in vivo recording of vessel diameter suggest that the cross-sectional compliance of large arteries can be unchanged or even increased in hypertensive subjects. The present study was performed to test the hypothesis that differences between volumetric and cross-sectional compliance could be related to differences in biaxial mechanical properties in normotensive and hypertensive rats. In normotensive (Wistar-Kyoto [WKY]) rats and spontaneously hypertensive rats (SHR) we measured the simultaneous changes in length and diameter of in situ isolated carotid arteries submitted to static pressures (50 to 200 mm Hg by steps of 25 mm Hg each). Carotid artery diameters and lengths were determined by video microscopy and computer-assisted image analysis. At low transmural pressure (50 mm Hg), carotid artery diameter was 710 +/- 41 microns in WKY rats and 980 +/- 31 microns in SHR (P < .01). In response to pressure increases, the carotid diameter increased by 91 +/- 6% in WKY rats and by 41 +/- 4% in SHR (P < .01). In parallel, the percent increase in carotid length was much larger in WKY rats than in SHR (31 +/- 2% versus 7 +/- 1%, respectively; P < .01). In WKY rats, longitudinal distensibility causes significantly larger volumetric values than cross-sectional compliance values; in contrast, because of the very small longitudinal distensibility, volumetric and cross-sectional compliances are almost identical in SHR.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanical and contractile properties of in situ localized mesenteric arteries in normotensive and spontaneously hypertensive rats

An in situ model was developed for studying mechanical properties of mesenteric arteries in rats. A branch of the mesenteric artery was exposed and dissected in normotensive (WKY) and spontaneously hypertensive rats (SHR). A catheter was introduced into the larger branch of the mesenteric artery and connected to a pressure chamber. The artery was submitted to transmural pressures ranging from 0 to 200 mmHg per steps of 25 mmHg and observed using a microscope-video-camera system. The diameter-pressure relations were established under basal conditions, under contraction (phenylephrine 10(-6) M), and after abolition of the smooth muscle tone by potassium cyanide (KCN, 0.1 mg/mL). The arterial segment was then fixed (glutaraldehyde 2.5%), and the wall cross-sectional areas were measured in transverse sections. Compliances, distensibility, wall tensions, and wall stresses were calculated from diameter, pressure, and media thickness values under three conditions. Active tension and active stress were defined as differences in wall stresses and wall tensions calculated under passive and active conditions. Comparison of WKY and SHR when arteries were studied at the respective operating pressure indicates (1) thicker and stiffer mesenteric arteries in SHRs than in WKY rats, (2) similar wall stresses in mesenteric arteries from WKY and SHRs despite larger wall tensions in the hypertensive group, and (3) larger contractility to phenylephrine in SHRs than in WKY mesenteric arteries.

Aminoguanidine treatment increases elasticity and decreases fluid filtration of large arteries from diabetic rats

The accumulation of advanced glycosylation end-products (AGEs) on collagen and the subsequent stiffening of this matrix protein in diabetes has been described many years ago. Structural modification of collagen in the arterial wall might have important effects on arterial elasticity. Aminoguanidine is known to decrease the formation of AGEs. In this study we evaluated the effects of aminoguanidine treatment on different parameters reflecting arterial wall elasticity in diabetic rats. We demonstrated that treatment of diabetic rats with aminoguanidine resulted in a significant increase in carotid static compliance (+39%, P < 0.01 under control conditions, and +27%, P < 0.01 after abolition of vascular tone by KCN), and a decrease in characteristic aortic input impedance (-40%, P < 0.01). The arterial pulse pressure in aminoguanidine-treated rats was decreased (-15%, P < 0.05) and the pulsatile component of left ventricular power output was relatively diminished (-35%, P < 0.05). In addition, we observed a lower fluid filtration across the carotid wall. These results indicate an increased vascular elasticity, an improved left ventricular-arterial coupling, and a decreased vascular permeability in diabetic rats after aminoguanidine treatment, suggesting that AGE-accumulation on collagen negatively affects arterial wall properties in experimental diabetes.

Long-term effects of angiotensin-converting enzyme inhibition on the arterial wall of adult spontaneously hypertensive rats

The effects of long-term angiotensin-converting enzyme (ACE) inhibitor treatment with perindopril 2 mg/kg/day, by gavage, for 3 months on the mechanical function and structure of large arteries were studied in adult spontaneously hypertensive rats with established hypertension. Hemodynamic parameters, including instantaneous aortic blood flow and pressure, were recorded under anesthesia at the end of the treatment period. Systemic arterial compliance was calculated from aortic pressure and flow recordings; passive mechanical properties of the in situ localized carotid artery were measured. Histologic and morphologic parameters of the aortic media, including cross-sectional area and thickness, size, and density of smooth muscle nuclei and of elastin and collagen fibers, were measured using an automated image analysis system. ACE inhibitor treatment significantly decreased mean arterial pressure (-27%, p < 0.001) and total peripheral resistance (-30%, p < 0.05) while cardiac output was increased (29%, p < 0.05). Systemic arterial compliance and carotid compliance were both increased by treatment (63%, p < 0.05, and 83%, p < 0.05, respectively). Morphometric assessment of vascular structure showed that ACE inhibitor treatment significantly decreased medial cross-sectional area (-36%, p < 0.001) and thickness (-16%, p < 0.001) by affecting smooth muscle cell hypertrophy (nucleus size decreased by 26%, p < 0.05) without changes in smooth cell number. Collagen density was decreased by treatment (-42%, p < 0.05), whereas elastin density was not affected by treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin does not regulate vascular smooth muscle Na+, K(+)-ATPase activity in rabbit aorta

To determine whether insulin regulates vascular smooth muscle Na+, K(+)-ATPase activity and if impaired insulin stimulation of vascular smooth muscle Na+, K(+)-ATPase activity could be a cause of increased vascular reactivity to norepinephrine and angiotensin II in diabetic states, the effects of insulin on Na+, K(+)-ATPase activity were examined in normal rabbit aortic intima-media incubated with normal plasma glucose and myo-inositol levels for 30 min. Insulin at 100 microU/ml (600 pmol/l) had no effect on Na+, K(+)-ATPase activity. At 250 microU/ml it caused a 4.2 +/- 0.8% increase, and at 500 microU/ml insulin caused a 17.7 +/- 1.4% increase in Na+, K(+)-ATPase activity that was completely inhibited by amiloride (1 mmol/l). Human insulin-like growth factor I (600 pmol/l) caused an 18.0 +/- 1.0% increase in Na+, K(+)-ATPase activity that was inhibited by amiloride. Insulin does not regulate (stimulate) aortic vascular smooth muscle Na+, K(+)-ATPase activity. Supraphysiological insulin concentrations, probably acting through an insulin-like growth factor I receptor, stimulate Na+/H+ exchange in aortic vascular smooth muscle and cause small secondary increases in Na+, K(+)-ATPase activity. In aortic intima-media incubated with normal plasma glucose and myo-inositol levels, endogenously released adenosine stimulates and maintains a component of resting Na+, K(+)-ATPase activity and stimulates acute increases in activity when norepinephrine (1 mumol/l) or angiotensin II (100 nmol/l) is added. These adenosine-stimulated components of Na+, K(+)-ATPase activity are selectively inhibited when the medium glucose is raised to 30 mmol/l during a 30-min equilibration and 30-min incubation.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanisms in rabbit aorta for hyperglycaemia-induced alterations in angiotensin II and norepinephrine effects

The (Na+,K+)-ATPase activity operative in rabbit aortic intima-media incubated with normal plasma levels of glucose and myo-inositol (70 mumol/l) is decreased when the glucose content of the medium is raised from 5 to 10 mmol/l or higher; this effect is prevented by aldose reductase inhibitors and by raising the myo-inositol content of the medium to 500 mumol/l. The decrease in (Na+,K+)-ATPase activity results from the loss of a component normally regulated (stimulated) by endogenously released adenosine through a receptor that stimulates phosphatidylinositol turnover in a discrete pool. The replenishment of this phosphatidylinositol pool selectively requires myo-inositol transport and is inhibited when increased polyol pathway activity impairs myo-inositol transport at a normal plasma level. Adenosine is a vasodilator, some endothelium-released vasodilators modulate the responses to vasoconstrictors by stimulating an increase in (Na+,K+)-ATPase activity in vascular smooth muscle. Whether adenosine mediates this effect in angiotensin II or norepinephrine-stimulated aorta was examined. Angiotensin II (100 nmol/l) and norepinephrine (1 mumol/l) evoked marked increases in (Na+,K+)-ATPase activity in aortic intima-media incubated with 5 mmol/l glucose and 70 mumol/l myo-inositol, which were inhibited when adenosine deaminase was added or the medium myo-inositol omitted to inhibit myo-inositol transport. Raising the medium glucose to 30 mmol/l inhibited the angiotensin II and norepinephrine-evoked increases in (Na+,K+)-ATPase activity, and this was prevented when tolrestat (10 mumol/l) was added or the myo-inositol content of the medium was raised from 70 to 500 mumol/l.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of various blood-derived and semisynthetic nutrient media on in vitro uptake of 125I-albumin across the intact porcine aortic endothelial surface in an organ-support system

The effects on porcine arterial structure and permeability of a 4-hour in vitro incubation at 37 degrees 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/c0 cm) of porcine 125I-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/c0 from the autogenous serum (AS) medium was used as the "control" measurement in each vessel preparation. (Grand mean M/c0 for AS from all studies was 0.312 +/- 0.011 [x10(-3)] [mean +/- SEM] cm, n = 60.) For brevity, M/c0 values from the other media are expressed below as a percentage of the corresponding paired M/c0 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 (less than 4-hour) metabolic support of the endothelial surface and subjacent tissues.

Preservation of endothelial cells in excised rat carotid arteries. Effects of transmural pressure and segment length

When arteries are excised, they collapse and shorten spontaneously, which can result in damage to the endothelium. To determine if an intact endothelial cell layer could be preserved in excised vessels, we isolated and cannulated rat carotid artery segments (in situ length, Lis, 10-20 mm) at both ends while maintaining both transmural pressure (70 mm Hg) and Lis, while either transmural pressure or Lis, or after allowing vessel collapse and shortening (n = 4 vessels per treatment). After each treatment, vessel segments were perfused with fixative and stained with AgNO3 to visualize endothelial cells. The amount of endothelial cell loss was quantified using stereological analysis of video microscopic images of the luminal surface. Results demonstrated that maintenance of both Lis and transmural pressure minimized endothelial cell denudation (1.6 +/- 0.9%); permitting the vessel to collapse and shorten resulted in the greatest loss of endothelial cells (59.4 +/- 13.2%); and maintenance of either pressure or Lis resulted in intermediate endothelial cell loss (13-30%). We conclude that the spontaneous collapse and shortening that normally accompany the excision of arterial segments result in substantial endothelial cell loss, which can be virtually eliminated with the maintenance of transmural pressure and vessel segment length. These findings have implications for surgical and experimental procedures requiring intact endothelium.

Fibronectin biosynthesis in the rat aorta in vitro. Changes due to experimental hypertension

This study was undertaken to determine if changes in fibronectin biosynthesis accompany the phenotypic changes that occur in aortic tissue following experimental hypertension. An in vitro procedure was developed to measure fibronectin synthesis in aortic rings obtained from normotensive or hypertensive rats. There was a three to sixfold increase in fibronectin biosynthesis by aortic rings taken from rats treated with deoxycorticosterone/salt for 7 and 21 d, the change being more pronounced at 21 d. In contrast, there was no major change at either time point in net incorporation into total protein. Studies comparing fibronectin biosynthesis in aortic rings from Wistar rats and spontaneously hypertensive rats at ages between 10 and 40 wk showed increased fibronectin biosynthesis in older animals of both strains, but only slight differences between strains. Studies using rats infused with angiotensin II showed a correlation between blood pressure elevation and increased aortic fibronectin biosynthesis. Western blot analysis of aortic extracts showed that the fibronectin content was increased in the hypertensive models. The in vitro procedure for measuring fibronectin biosynthesis appears to provide a reliable reflection of in vivo changes in fibronectin expression, and the methodology could prove useful for studying the factors influencing protein expression in vascular tissue.

Effects of alpha 1-blockade on arterial compliance in normotensive and hypertensive rats

The effects of blockade of alpha 1-adrenergic receptors on the mechanical properties of the arterial wall were studied in 10 spontaneously hypertensive rats (SHR) as compared with 10 matched normotensive Wistar-Kyoto (WKY) rats. Ascending aortic pressure and flow were recorded in open-chest anesthetized rats, and the systemic arterial compliance was calculated. Intravenous injection (1 mg/kg) of Urapidil, a selective alpha 1-adrenergic antagonist, induced a significant decrease in arterial pressure (-26%, p less than 0.01 and -37%, p less than 0.001 in WKY rats and SHR, respectively) without significant changes in cardiac output. In control conditions, systemic arterial compliance was lower in SHR (3.29 +/- 1.52 microliters/mm Hg) than in WKY rats (4.35 +/- 1.35 microliters/mm Hg, p less than 0.01). Urapidil injection induced significant increases in systemic arterial compliance values in both strains (p less than 0.001). In another set of experiments (15 WKY rats and 15 SHR), the carotid compliance (microliters/mm Hg) was determined from the arterial volume-pressure relation under control conditions, after local incubation with Urapidil, and after total abolition of the vascular smooth muscle by KCN. In WKY rats, the carotid compliance increased markedly after incubation with Urapidil at doses corresponding to 1 mg/kg (+31%, p less than 0.01). A further increase in the carotid compliance was observed after KCN poisoning (+11%, p less than 0.05). In SHR, incubation with Urapidil at doses corresponding to 2 mg/kg were necessary to induce a significant increase in compliance (+38%). At this dosage, there was no further increase in compliance after KCN poisoning.(ABSTRACT TRUNCATED AT 250 WORDS)

Elevated extracellular glucose inhibits an adenosine-(Na+,K+)-ATPase regulatory system in rabbit aortic wall

The mechanism by which hyperglycaemia causes decreased (Na+,K+)-ATPase activity preventable by aldose reductase inhibitors and by raising plasma myo-inositol in specific tissues can be activated in vitro in normal rabbit aortic wall; it selectively inhibits a component of resting (Na+,K+)-ATPase activity maintained by a novel regulatory system through rapid basal phosphatidylinositol turnover (hydrolysis) in a discrete pool, which is replenished by a fraction of phosphatidylinositol synthesis that selectively requires myo-inositol transport. A role for endogenously released adenosine in this regulatory system was examined. Adding adenosine deaminase or 8-phenyltheophylline, an adenosine receptor antagonist, selectively inhibited the component of (Na+,K+)-ATPase activity maintained by the regulatory system; when inhibited with adenosine deaminase this component was restored by 2-chloroadenosine, 5'-N-ethylcarbox-amidoadenosine, and 1-oleoyl-2-acetylglycerol, but not by forskolin (which also did not inhibit this component). Adenosine deaminase inhibited the rapid basal turnover of the discrete phosphatidylinositol pool, and 2-chloroadenosine then stimulated its turnover. Raising medium glucose from 5 to 10-30 mmol/l inhibits the regulatory system by making myo-inositol transport at a normal plasma level inadequate to maintain the replenishment of the discrete phosphatidylinositol pool. 2-Chloroadenosine stimulation of the "adenosine-sensitive" component of (Na+,K+)-ATPase activity was inhibited in tissue incubated with 30 mmol/l glucose and myo-inositol in a normal plasma level, but this effect was demonstrable when the medium myo-inositol was raised seven-fold. Hyperglycaemia-induced decreased (Na+,K+)-ATPase activity that is preventable by aldose reductase inhibitors and by raising plasma myo-inositol results from the inhibition of a novel adenosine-(Na+,K+)-ATPase regulatory system.

Technical considerations in evaluating the endothelial integrity of rat aortic preparations with silver staining

Assessment of endothelial integrity is an obligatory step in many pharmacological studies. Integrity of endothelium is affected by manipulations performed during the removal and cleaning of the vessel and by some of the silver-staining techniques utilized for demonstrating interendothelial junctions. When aortas were cleaned of periadventitial tissue in cold Tris-saline (once separated from the animal) by untrained personnel, only 45% of the endothelium was preserved. When cleaning was performed in situ by trained personnel while flushing with cold Krebs-Ringer-6% albumin, over 95% was left intact. AgNO3-staining performed before fixation produced a 50% loss of endothelium when using NH4Br and (NH4)2S as developers. AgNO3-staining performed after fixation produced over 95% recuperation of endothelium when 2% glutaraldehyde, 150 mM NaCl, 40 mM phosphate buffer, pH 7.4, were utilized as initial fixative, NH4Br and (NH4)2S being equally effective as developers. Chloride ions were necessary to intensify silver lines. Several patterns of deendothelization were produced by mechanical and chemical injury with saponin, NH4Br and (NH4)2S. In all cases, hematoxylin staining was employed as an auxiliary technique to interpret images of injured endothelium. Presence of albumin protected the endothelium from mechanical damage.

Experimental induction of spasm, sudden progression of organic stenosis and intramural hemorrhage in the epicardial coronary arteries

Pathogenesis of the so-called "heart attack" still remains to be elucidated. The links between stable effort angina and unstable or acute myocardial infarction, and between asymptomatic and spontaneous angina are all missing. In medicine presently, pathophysiology of ischemic heart disease is considered a consequence of i) the progression of atherosclerotic narrowing of the coronary artery, and ii) dynamic and transient obstruction (coronary spasm), but these mechanisms are traditionally believed to be unrelated. This article demonstrates various experimental evidence indicating that these two mechanisms are related. And, this review article describes how to produce experimental coronary spasm in the presence of atherosclerosis, similar to that seen in patients with variant angina, and that coronary spasm can produce sudden progression of coronary atherosclerotic obstruction due to intramural hemorrhage. Establishment of various animal models to elucidate mechanisms related to various stages of ischemic heart disease are needed.

Nucleotide profiles in normal minipig arterial tissue

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 normocholesterolemic, anesthetized minipigs. In three animals, transmural myocardial samples were also obtained. Nucleotide and nucleoside concentrations were analyzed by using a recently developed ion-pairing, reverse-phase, high-performance liquid chromatographic method. The arterial samples contained relatively low concentrations of adenosine triphosphate, approximately one-eighth that of the myocardial counterpart. Relative to the femoral artery, the aortic samples had significantly lower adenylate energy charges and higher levels of adenosine diphosphate, adenosine monophosphate, adenosine, and inosine. 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.

Endothelium-dependent mechanical properties of the carotid artery in WKY and SHR. Role of angiotensin converting enzyme inhibition

An experimental model of in situ isolated carotid arteries has been used to evaluate the static mechanical properties of the arterial wall in 12-week-old Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR). The effects of endothelium removal and of local incubation with the converting enzyme inhibitor lisinopril (ICI Pharma 209000) on the carotid compliance (CC) were compared with the effects of total abolition of the vascular smooth muscle tone by potassium cyanide. CC measured for pressures ranging from 50 to 175 mm Hg had maximal values (0.22 +/- 0.07 microliter/mm Hg and 0.13 +/- 0.03 microliter/mm Hg, respectively, for WKY and SHR, p less than 0.001) for pressure values close to the operating pressures in both groups. Maximal values of CC were increased by 35% and 45% in WKY and SHR, respectively, after potassium cyanide poisoning (p less than 0.01). The endothelium removal induced a significant increase in CC compared with their control values (+37%, p less than 0.01, and +25%, p less than 0.01, respectively, in WKY and SHR). CC measured after endothelium removal did not significantly differ from its values measured after potassium cyanide poisoning in normotensive animals. In contrast, in hypertensive animals, CC was significantly lower after endothelium, removal than after potassium cyanide poisoning (p less than 0.01). In the presence of intact endothelium, local incubation with converting enzyme inhibitor increased CC by 23% (p less than 0.05) in WKY rats and by 14% (p less than 0.01) in SHR. In contrast, after endothelium removal, converting enzyme inhibitors did not significantly increase further CC in either strain.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanism of glucose-induced (Na+, K+)-ATPase inhibition in aortic wall of rabbits

Hyperglycaemia decreases (Na+, K+)-ATPase activity in specific tissues by a mechanism whose effects are prevented by aldose reductase inhibitors and by raising plasma myo-inositol. This mechanism was activated and studied in vitro in normal rabbit aortic intima-media. Raising medium glucose to 10 mmol/l for 60 min inhibited a major component of (Na+, K+)-ATPase-mediated 86Rb+/K+ uptake normally operative in resting aortic intima-media in medium containing normal plasma levels of glucose (5 mmol/l) and myo-inositol (70 mumol/l); 20 or 30 mmol/l glucose had no greater effect. This effect occurred under conditions in which the aortic intima-media's normal myo-inositol content is not detectably decreased. The inhibition was prevented by sorbinil (10 mumol/l) and by raising medium myo-inositol from 70 to 500 mumol/l, which had no effect on (Na+, K+)-ATPase activity when the medium glucose remained at 5 mmol/l. Raising medium glucose selectively inhibited a component of (Na+, K+)-ATPase activity that requires medium myo-inositol, because it is maintained by a regulatory system through rapid basal phosphatidylinositol turnover in a discrete pool, which is replenished by a fraction of basal de novo phosphatidylinositol synthesis that is selectively dependent on myo-inositol uptake. Medium myo-inositol at a normal plasma level became inadequate to maintain this fraction of basal de novo phosphatidylinositol synthesis [( 1,3-14C]glycerol incorporation) when the medium glucose was raised. When sorbinil was added raising medium glucose did not alter the ability of 70 mumol/l medium myoinositol to maintain the (Na+, K+)-ATPase activity that requires medium myo-inositol.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of varying albumin concentration of the hydraulic conductivity of the rabbit common carotid artery

Rabbit common carotid arteries were cannulated in situ, after ligation of their branches, and transferred to a perfusion apparatus in such a way that they were maintained at their physiological dimensions and the endothelium remained intact. The vessels were pressurized to 150 cm H2O with Krebs solution and the wall smooth muscle was relaxed with 10(-4) M NaNO2. The rate of inflow of perfusate into the vessels was measured by following the movement of a bubble in a calibrated capillary which, when steady, was taken to indicate the transmural filtration rate. The filtration rate was 1.48 +/- 0.26 X 10(-6) cm sec-1 (11) (mean, SD, n) with 1 g/dl bovine serum albumin in Krebs solution. The values with 0, 4, 7, and 10 g/dl, normalized by the 1 g/dl value were 1.38 +/- 0.16 (7), 0.80 +/- 0.05 (9), 0.65 +/- 0.03 (8), and 0.47 +/- 0.06 (9), respectively. The hydraulic conductivity of the wall was also found to depend on perfusate albumin concentration. The 1 g/dl value was 0.92 +/- 0.17 X 10(-8) cm sec-1 (cm H2O)-1 (11) and the values with 0, 4, 7 and 10 g/dl normalized by the 1 g/dl value were 1.35 +/- 0.16 (7), 0.87 +/- 0.06 (9), 0.81 +/- 0.03 (8), and 0.72 +/- 0.06 (9), respectively. The findings were analyzed in relation to models involving interaction of albumin with the endothelial glycocalyx, concentration polarization at the blood/wall interface, dependence of flux on solvent viscosity and dependence of the porosity of the wall interstitium on solvent flux. Both concentration polarization and variation of the porosity of the wall interstitium provide reasonable quantitative explanations for the findings.

Effect of insulin-like growth factor-I on metabolism in bovine mesenteric arteries

The effect of insulin-like growth factor-I (IGF-I) on glucose accumulation, amino acid uptake and incorporation of amino acid into protein was studied in arterial smooth muscle. Accumulation of [14C]glucose, uptake of [14C]alpha-aminoisobutyric acid (AIB) and incorporation of [14C]phenylalanine into protein were measured in intima-media preparations of bovine mesenteric arteries (BMA) incubated with IGF-I for 2, 4 or 6 h. IGF-I (2.2 nmol l-1) increased the accumulation of glucose into BMA after 4 h (P = 0.0079) and 6 h incubation (P = 0.0027) and in a concentration of 22 nmol l-1) also after 2 h (P = 0.015). The uptake of AIB and the incorporation of phenylalanine were increased after 4 h incubation with 2.2 nmol l-1) IGF-I (P = 0.0045 and P = 0.026, respectively). The effects of IGF-I on all of the metabolic parameters were dependent on incubation time and concentration of IGF-I. Concentration-effect curves were determined for the effect of IGF-I and also for insulin on glucose accumulation in BMA incubated for 6 h. The concentration-effect relationships for IGF-I and insulin were very similar with pD2 values of 7.6 +/- 0.2 (EC50 = 27 nmol l-1) and 7.5 +/- 0.2 (EC50 = 34 nmol l-1), respectively. No additive effect of IGF-I and insulin in supra-physiological concentrations (1.0 mumol l-1) could be demonstrated. These results show that IGF-I has metabolic effects which are similar to the effects of insulin in vascular smooth muscle and suggest that IGF-I may be of importance for the metabolism in vascular smooth muscle.

Glucose and fatty acid metabolism in normal and diabetic rabbit cerebral microvessels

Rabbit cerebral microvessels were used to study fatty acid metabolism and its utilization relative to glucose. Microvessels were incubated with either [6-14C]glucose or [1-14C]oleic acid and the incorporation of radioactivity into 14CO2, lactate, triglyceride, cholesterol ester, and phospholipid was determined. The inclusion of 5.5 mM glucose in the incubation mixture reduced oleate oxidation by 50% and increased esterification into both phospholipid and triglyceride. Glucose oxidation to CO2 was reduced by oleate addition, whereas lactate production was unaffected. 2'-Tetradecylglycidic acid, an inhibitor of carnitine acyltransferase I, blocked oleic acid oxidation in the presence and absence of glucose. It did not effect fatty acid esterification when glucose was absent and eliminated the inhibition of oleate on glucose oxidation. Glucose oxidation to 14CO2 was markedly suppressed in microvessels from alloxan-treated diabetic rabbits but lactate formation was unchanged. Fatty acid oxidation to CO2 and incorporation into triglyceride, phospholipid, and cholesterol ester remained unchanged in the diabetic state. The experiments show that both fatty acid and glucose can be used as a fuel source by the cerebral microvessels, and the interactions found between fatty acid and glucose metabolism are similar to the fatty acid-glucose cycle, described previously.

General mechanism of chronic diseases

In a human, the cells function adequately to the needs of the organism, and to their own needs. Consequently, adequate cell function is comprised of the organism-oriented, and cell-oriented functions. It is suggested that an independent stage in the pathogenesis of a chronic disease exists which so far has not been considered. This is the disturbance of the cell-oriented function of the cells involved. This initial stage may last for years and decades, whereas function of the organ remains preserved. Organism-oriented cellular function appears to become involved in the pathologic process long after the disease has actually started. At this time the cells themselves are severely impaired, and as a result a disease acquires its progressive, irreversible course. Pathogenesis of atherosclerosis is considered as an example of the above-mentioned developments.

Proteoglycans and hypertension. II. [35S]sulfate incorporation into aorta proteoglycans of spontaneously hypertensive rats

Spontaneously hypertensive (SH) rats are known to have an increased content of chondroitin sulfate (CS) proteoglycans (PG) in the aorta as compared to normotensive Wistar Kyoto (WKY) rats. In the present study we have compared WKY and SH rat aortas with respect to [35S]sulfate incorporation in vivo and in vitro. The specific activity (cpm/mg aorta) of the total glycosaminoglycan (GAG) pool from SH rat aorta, measured 48 h after intraperitoneal injection of [35S]sulfate, was twice as high as that of WKY aorta GAG. After in vitro incubation of aortas for 4 or 6 h, the specific activity (cpm/mg aorta) of glycosaminoglycans from SH rat was 2.4- to 7.1-fold higher than in controls. Labeled PG were extracted with 4 M guanidine from aortas which had been incubated with [35S]sulfate, and chromatography of the extract on Sepharose CL-6B yielded two incompletely resolved peaks, one emerging with the void volume (peak I) and one in a more retarded position (peak II). Peak I (WKY) contained nearly equal amounts of CS and HS (53 and 46%, respectively) and a small amount of DS (8%). Peak II (WKY) (Kav, 0.34) was divided into two fractions; the fraction of larger molecular weight (II A) contained 43% CS, 35% DS, and 20% HS, whereas the smaller fraction (II B) contained 40% CS, 51% DS, and 5% HS. In each corresponding pool from SH rat aorta, a similar proportion of HS was found, but the DS content was approximately half, and the CS content was correspondingly greater. The estimated molecular weights of the CS/DS chains in peaks I, II A, and II B from WKY aorta were 34,600, 18,800, and 11,600 daltons, respectively, whereas the corresponding values for the SH rat aorta pools were 32,300, 24,700, and 17,000 daltons, respectively. The proportions of 4- and 6-sulfated galactosamine residues as well as the degree of sulfation of the CS/DS PG were similar in the two strains. The HS-PG was larger in the WKY rat aorta and was made up of larger HS chains (Mr 26,600 vs. 16,100); however, the degree of sulfation was apparently similar in the two strains. These results suggest that the rates of PG synthesis and/or degradation and the PG structure are altered in the SH rat aorta.

Basal phosphatidylinositol turnover controls aortic Na+/K+ ATPase activity

To determine whether basal phosphoinositide turnover plays a role in metabolic regulation in resting rabbit aortic intima-media incubated under steady state conditions, we used deprivation of extracellular myo-inositol as a potential means of inhibiting basal phosphatidylinositol (PI) synthesis at restricted sites and of depleting small phosphoinositide pools with a rapid basal turnover. Medium myo-inositol in a normal plasma level was required to prevent inhibition of a specific component of basal de novo PI synthesis that is necessary to demonstrate a discrete rapidly turning-over [1,3-14C]glycerol-labeled PI pool. Medium myo-inositol was also required to label the discrete PI pool with [1-14C]arachidonic acid (AA). The rapid basal turnover of this PI pool, when labeled with glycerol or AA, was not attributable to its utilization for polyphosphoinositide formation, and it seems to reflect basal PI hydrolysis. Depleting endogenous free AA with medium defatted albumin selectively inhibits the component of basal de novo PI synthesis that replenishes the rapidly turning-over PI pool. A component of normal resting energy utilization in aortic intima-media also specifically requires medium myo-inositol in a normal plasma level and a free AA pool; its magnitude is unaltered by indomethacin, nordihydroguaiaretic acid, or Ca2+-free medium. This energy utilization results primarily from Na+/K+ ATPase activity (ouabain-inhibitable O2 consumption), and in Ca2+-free medium deprivation of medium myo-inositol or of free AA inhibits resting Na+/K+ ATPase activity to a similar degree (60%, 52%). In aortic intima-media basal PI turnover controls a major fraction of resting Na+/K+ ATPase activity.

Endothelial injury and healing in vitro. Studies using an organ culture system

The authors have developed an organ culture system in which segments of rabbit aorta were used for the study of the healing of superficial, intimal injury analogous to that produced in vivo by a nylon monofilament catheter. Aortic segments containing an intact endothelial monolayer were obtained for culture by careful avoidance of the damaging consequences of loss of vascular pressure, vasocontraction, and thrombosis. The segment could be maintained in culture for several weeks. Repair of superficial injury was studied after placing a series of precisely located injuries, 100 mu wide, on each aortic segment over a period of several days. The pattern of healing observed was similar to that observed in vivo. The wounded area was recovered by migrating cells within 24 hours, and during succeeding days these cells underwent a predictable pattern of remodeling which restored the normal morphologic features of the endothelium. The cells within the wound underwent a burst of cell division between 24 and 96 hours after injury and subsequently became quiescent. This organ culture approach potentially allows the investigation of many consequences of endothelial injury in a system which provides far greater control and manipulation of the cellular environment than is possible in vivo.

Separation of aerobic glycolysis from oxidative metabolism and contractility in rat anococcygeus muscle

The relationship of aerobic glycolysis (JLac) and O2 utilization (JO2) to contractility and the activity of the Na+-K+ pump was investigated in rat anococcygeus smooth muscle. Removal of extracellular potassium concentration ([K+]o) caused an initial increase followed by a decrease in JLac below the resting rate. Restoration of [K+]o caused JLac to increase, and this response, but not the initial one observed in zero [K+]o, was prevented by ouabain. These changes in JLac were not related to contractility, since a similar response was observed in both phentolamine-treated and chemically denervated muscles that exhibited minimal force and no significant changes in JO2. Tension development of innervated muscles incubated in K+-free medium was related to changes in JO2. A logarithmic relationship between JLac and [K+]o suggested that changes in JLac resulted from effects on glucose transport or utilization secondary to changes in the membrane potential. In stimulated muscles JLac and JO2 were both positively correlated with isometric force and were not affected by ouabain. Separation of JLac from JO2 and force production under some conditions supports the hypothesis that a functional compartmentalization of metabolic pathways exists in anococcygeus muscle.

Compartmentation of glycolytic and glycogenolytic metabolism in vascular smooth muscle

Vascular smooth muscle is characterized by a high rate of aerobic lactate production, which may be altered independently of oxidative phosphorylation. This finding suggested a cytoplasmic compartmentation of metabolism. Exogenous glucose was found to be the sole precursor of aerobic glycolysis under unstimulated conditions. Although tissue depolarization with high K+ resulted in a substantial reduction of endogenous glycogen, exogenous glucose remained the sole precursor of aerobic lactate production. These data showed unequivocally that carbohydrate metabolism is compartmentalized in vascular smooth muscle.

A system for long-term perfusion of rabbit aorta in vitro

In an in vitro system for the perfusion of arterial tissue, the volume of the incubation chamber should be small, and the composition of the medium should be easily modified. The tissue should consist of media and intima only, and the interaction with the medium should occur via the intimal side. Consecutive sampling of the medium and the tissue should be possible. This paper describes a system with these characteristics. Scanning and transmission electron microscopy of the perfused tissue indicated that the endothelium was intact during the first day and that it still covered more than 95% of the surface after 3 days. On the 2nd day, the nonthrombogenic properties of the endothelium were maintained. The medial smooth muscle cells of the inner two-thirds of the preparation were viable during the perfusion, while the cells in the outer one-third were dead from the start. Still, the metabolic activity of the tissue was stable, at least during the 2nd day as assessed by the study of DNA, protein, and lipid synthesis, as well as by oxygen consumption. We conclude that the perfusion system presented here might be useful in the study of the interaction between cellular and humoral components of the blood and the arterial wall.

Coronary artery spasm in intact dogs induced by potassium and serotonin

Although coronary artery spasm has been implicated as an important cause of myocardial ischemia in humans, an animal model of reversible segmental coronary constriction has not been described. To provoke coronary spasm in open-chest dogs, selected vasoconstricting agents adsorbed to viscous ion exchange gels were applied topically to the surface of epicardial coronary arteries. The procedure provided a sustained localized release of drug, and minimized effects on contiguous myocardium or on the systemic circulation. Segmental arterial constrictor responses were evaluated by sonomicrometry, arteriography, and electromagnetic flow measurements. Potassium evoked sustained constrictions or spasms, and concomitantly reduced flow by -42 +/- 4% (SE; n = 34). Serotonin likewise produced sustained decreases in flow of -22 +/- 6% (SE; n = 5). Other constrictors, including norepinephrine and angiotensin, failed to evoke sustained constrictions. Spasms nearly abolished reactive hyperemic responses elicited by temporary complete occlusion of the artery. Intravenous nitroglycerin and dihydropyridine calcium antagonists promptly relieved the spasms. Scanning electronmicroscopic examination of the intimal surface of arteries undergoing sustained spasm revealed no platelet thrombi. Thus, nonthrombotic, vasodilator-sensitive segmental coronary spasms were elicited by endogenous constrictors which may play a role in regulating flow to ischemic myocardium.

Metabolic changes in modified smooth muscle cells of rabbit carotid arteries

In the common carotid artery of rabbits, intimal myocyte proliferations were induced by daily repeated local electrical stimulation of the vessel wall in combination with a cholesterol containing diet given for 4 weeks. Some biochemical parameters of the morphologically modified intimal smooth muscle cells were studied and compared with those of samples obtained from nonstimulated tunica media of the contralateral carotid artery. The results show that in relation to dry weight both alkali extractable protein and DNA content of the proliferates are increased to about 125%. In the proliferates, the in-vivo tissue concentrations of glucose and glycogen are only 50-70% of the normal values, whereas the concentration of lactate is increased to about 160%. In-vitro incubation experiments of excised tissues samples from the intimal proliferates and normal media indicate that under an optimal supply of substrates the glucose uptake and lactate production of the proliferates are increased to 140% and 150%, respectively. This results provides evidence for an increased capacity of glycolysis in the proliferates, which in vivo may lead to a decrease in glucose concentration and to an increased concentration of lactate. This investigation shows that modified smooth muscle cells proliferating in the arterial intima exhibit an activated metabolism as seen in other models of arteriosclerosis.

The utilization by rabbit aorta of carbohydrates, fatty acids, ketone bodies, and amino acids as substrates for energy production

The ability of rabbit aorta to oxidize various substrates was studied to determine which of these compounds may be energy substrates for vascular smooth muscle (VSM). Glucose, ketone bodies, medium-chain length fatty acids, branched-chain amino acids, and glutamine all are oxidized at comparable rates on a molar basis. Some other amino acids, long chain fatty acids, pyruvate and glycerol also are oxidized, but at lower rates. The oxidation of 6 amino acids could not be detected. VSM was found to release ketone bodies when incubated in leucine beta-hydroxybutyrate or octanoate. This suggests that the acetoacetyl CoA and/or acetoacetate derived from these substrates is not completely oxidized. The oxidation rate of several substrates when measured individually is inhibited by 50-80% by the presence of a combination of other substrates in the medium. Under these conditions, glucose is a minor substrate for oxidative metabolism accounting for only 5% of O2 consumption. The oxidation rate of all the exogenous substrates together is calculated to account for less than half of the oxygen consumption; this finding indicates that an endogenous substrate must also be utilized.

Hexose transport in normal and SV40-transformed human endothelial cells in culture

The mechanism of glucose entry into human vascular endothelial cells was studied in monolayer cultures of normal (primary) and virally (SV40) transformed umbilical vein endothelium. Radioisotopic uptake studies with the glucose analogues 2-deoxy-D-glucose, and 3-O-methyl-D-glucose, and the nonmetabolizable stereoisomer L-glucose, indicated the presence of a saturable, stereospecific hexose carrier mechanism in both cell types. In other experiments with D-glucose and 3-O-methyl-D-glucose, the phenomenon of countertransport was demonstrable. Hexose transport was not affected by KCN, dinitrophenol, or ouabain, but was inhibited by phloretin and phlorizin in a pattern consistent with facilitated diffusion. Kinetic constants were obtained for both 2-deoxy-D-glucose and 3-O-methyl-D-glucose uptake. Similar Km values (range, 3.3-4.7 mM) were noted with normal and transformed cells, whereas the apparent Vmax was 0.56 nmol/microliter cytosol/minute for primary cells and 1.7-2.5 nmol/mu cytosol/minute for transformed cells. Under standard culture conditions, as well as following 18 hours of serum deprivation, insulin at concentrations up to 10(-5) M did not appear to influence hexose uptake in either cell type. Metabolism of 14C(U)-D-glucose to 14CO2 also was not stimulated by insulin. The presence of an insulin-insensitive, facilitated transport system for glucose in vascular endothelium has relevance for glucose metabolism in this tissue, and potentially for the association of certain vascular diseases (e.g., diabetic microangiopathy, atherosclerosis) with altered glucose homeostasis.

Blood flow and scanning electron microscope study on venous microvascular anastomoses with Nakayamas apparatus and manual suture

Endothelium repair and blood flow changes after microvascular anastomoses in rabbit neck veins (diameter 1.5-2.5 mm) with either Nakayamas apparatus or manual suture were studied with scanning electron microscope and electromagnetical flowmeter. The healing process, which was very rapid, was examined at varying intervals from the day of surgery to four weeks postoperatively. Complete endothelialization was evident after one week. The blood flow was unimpaired by anastomosis with Nakayama rings, whereas in the suture group reduction in blood flow followed immediately after surgery. This reduction was however transient and blood flow was normalized two hours postoperatively.

The normal healing process of microvascular anastomoses

The vessel wall regeneration and the inflammatory response in the rabbit femoral artery and vein the first three months after microvascular end-to-end suture anastomosis was assessed histologically. The initial damage consisted of endothelial loss and partial necrosis of media and adventitia. The luminal surface was reendothelialized and the adventitial layer restored by 20 days, but the necrotized part of the media did not regenerate. Instead, the vessel wall diameter was maintained by an intimal hyperplastic response. At the anastomotic site a characteristic slight dilatation was persistent. Consequently, the vessel wall architecture was not restored to the preoperative state after microvascular anastomosis.

Effects of in vitro and in vivo exposure to insulin upon glucose carbon accumulation in rat aorta: different patterns of response for intima-media and adventitia

We have studied the effect of insulin upon the accumulation of glucose carbon into the intima-media and the adventitia of rat aorta following in vitro exposure by adding insulin to the incubation medium, and in vivo exposure by producing relative hyperinsulinemia during life and subsequently incubating excised tissue in a medium containing no insulin. Hyperinsulinemia in vivo was either (1) endogenous--following 1.5-2 hr of refeeding after a 48-hr fast--or (2) exogenous--following an i.v. injection of insulin. For adventitia, a significant stimulation was found after both in vitro (+ 53%, p < 0.001) and in vivo exposure to insulin (+ 96%, p < 0.01 with endogenous insulin; + 75%, p < 0.05 with a dosage of 2 U/kg of exogenous insulin). For intima-media, the stimulation was weak and insignificant after in vitro exposure (+ 11%, p > 0.30), but became important and significant after in vivo exposure to insulin (+ 100%, p < 0.001 with endogenous insulin; + 50%, p < 0.05 with a dosage of 0.5 U/kg and + 49%, p < 0.05 with a dosage of 2 U/kg of exogenous insulin). For the in vivo exposure experiments, we found a significant linear correlation (r = 0.611, p < 0.005) between plasma insulin concentrations and glucose carbon accumulations into intima-medias of control and refed rats. These results establish the insulin sensitivity of the adventitia and show a sensitivity of intima-media only to in vivo insulin exposure. These different behaviors of intima-media in vivo and in vitro may have a hemodynamic basis.