Interleukin 2 acutely induces platelet and neutrophil-endothelial adherence and macromolecular leakage.

The acute effects of interleukin 2 (IL-2) were determined in the rat cremaster microcirculation model by intravital, light, and electron microscopy to better understand the pathophysiology of the IL-2-induced vascular leak syndrome. Four groups of rats were studied over a 2-h monitoring period. One group received 1 x 10(6) units of IL-2/kg i.v. (n = 10), while the remaining groups received IL-2 topically applied to the cremaster muscle in dosages of either 1 x 10(5) (n = 9), 1 x 10(6) (n = 5), or 3 x 10(6) (n = 5) units. Each group was compared with controls (n = 9). IL-2 administered i.v. acutely induced platelet and polymorphonuclear leukocyte-endothelial adherence and microvascular macromolecular leakage that occurred synchronous with the development of tachycardia, hypotension, tachypnea, and hypoxemia. Topically applied IL-2 induced similar microvascular alterations but without changes in hemodynamic and respiratory parameters, which suggests that microvascular alterations were not caused by IL-2-induced changes in hemodynamic parameters. Electron microscopy of cremaster muscle sections demonstrated platelet and neutrophil adherence to the endothelium and endothelial injury. We conclude that IL-2 (or a locally generated mediator) acutely induces platelet and neutrophil-endothelial adherence in the rat skeletal muscle microcirculation that is associated with the development of macromolecular leakage from the microcirculation.

Platelet aggregation and adhesion during dietary copper deficiency in rats.

The role of dietary copper deficiency in platelet-to-endothelial cell adhesion and in platelet-to-platelet aggregation was studied in vitro. Platelets were obtained from male, weanling Sprague-Dawley rats fed purified diets which were either copper-adequate (CuA, 6.3 micrograms copper/g of diet) or copper-deficient (CuD, 0.3 microgram/g of diet) for 4 weeks. The platelet adhesion study was performed by adding CuA or CuD platelets either suspended in homologous plasma or in Tyrode buffer salt solution (TBSS) to cultured rate endothelial cells. After a one hour incubation at 37 degrees C non-adhered platelets were removed and counted in a microcytometer. Platelet aggregation in platelet rich plasma (PRP) samples was induced by adding ADP (2 x 10(-4)M) and measured in a turbidometric aggregometer. The content of von Willebrand factor (vWF) in platelets and in plasma and the content of fibrinogen in platelets was determined. Platelet adhesion to rat endothelial cells was significantly lower for platelets from CuD rats than for platelets from CuA rats. ADP induced platelet aggregation from CuD rats was significantly higher than platelet aggregation from CuA rats. The content of vWF in platelets and in plasma from CuD rats was significantly lower than in platelets and plasma from CuA rats. However, the amount of fibrinogen in platelets from ++CuD rats was about 4-fold higher than that in platelets from CuA rats while the plasma fibrinogen was lower in CuD rats than in CuA rats. These studies illustrate that copper deficiency diminishes platelet adhesion to endothelial cells but increases platelet aggregability. The results suggest that these physiological alterations may be the result of decreased platelet vWF and increased platelet fibrinogen during dietary copper deficiency.

Leukocyte-endothelial adhesion is impaired in the cremaster muscle microcirculation of the copper-deficient rat.

Dietary copper deficiency impairs the function of both the vascular endothelium and circulating leukocytes. In the current study, leukocyte-endothelium adhesion was observed in the in vivo cremaster muscle microcirculation of copper-adequate and copper-deficient rats. Male, weanling Sprague-Dawley rats were fed purified diets that were either adequate (5.6 microg/g) or deficient (0.3 microg/g) in copper. Adhesion was stimulated with the inflammatory mediators tumor necrosis factor-alpha and bradykinin, and the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine. Intravascular adhesion of leukocytes to the vascular endothelium was significantly attenuated in the copper-deficient group in response to all three agonists. These results occurred without any difference in intravascular wall shear rate between the dietary groups. Based on previous work, we propose that the attenuated response is caused by either decreased expression of adhesion molecules on leukocytes and endothelial cells or by inhibition of the endothelial cell calcium signaling associated with copper deficiency.

Endothelial cell calcium mobilization to acetylcholine is attenuated in copper-deficient rats.

Dietary copper deficiency significantly attenuates nitric oxide (NO)-mediated vascular smooth muscle relaxation and vasodilation. There is evidence for both increased inactivation of the NO radical by superoxide anion, and oxidative damage to the endothelium where NO is produced. The current study was designed to examine the NO synthetic pathway in the endothelium during copper deficiency. Male weanling rats were fed a copper-adequate (CuA, 6.4 mg Cu/kg diet) or copper-deficient (CuD, 0.4 mg Cu/kg diet) diet for four weeks. Cremasteric arterioles (approximately 100 microm diameter) were isolated and used for the experiments. Western blot analysis of the arteriole endothelial nitric oxide synthase (eNOS) concentration did not show a difference between dietary groups. Acetylcholine (Ach)-induced vasodilation was significantly reduced in the CuD group both before and after pretreatment with the eNOS substrate L-arginine. Endothelial intracellular calcium ([Ca2+]i) stimulated by 10(-6) M Ach was significantly inhibited in the arterioles from CuD rats. Coincident with the inhibition of [Ca2+]i and vasodilation was a depression of vascular Cu/Zn-SOD activity and an increase in plasma peroxynitrite activity. These data suggest that endothelial Ca2+ signaling and agonist-stimulated NO-mediated vascular dilation are likely reduced by increased oxidative damage in copper-deficient rats.

In vivo platelet thrombus formation in microvessels of spontaneously hypertensive rats.

Sustained high blood pressure causes functional changes in both vascular endothelial cells and platelets. Therefore, we hypothesized that in vivo platelet thrombus formation would be increased in the cremaster muscle microvessels of rats during genetic hypertension. Experiments were carried out on spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY) at 12 weeks of age. Fluorescein isothiocyanate tagged to bovine serum albumin (FITC-BSA) was injected intraarterially and 450 to 490 nm light was used to activate the FITC-BSA and induce a thrombus within the vasculature. In vivo television microscopy was used to quantitate thrombus formation and microvascular diameter changes. The time of platelet thrombus initiation and subsequent time of thrombus growth were studied at wall shear rates of approximately 2000 sec(-1) and 270 sec(-1) in third-order arterioles and venules, respectively. In SHR, times for platelet thrombus initiation and vessel occlusion were significantly less in both arterioles and venules, whereas time for platelet thrombus growth following initiation was significantly prolonged. Greater shear rates in arterioles compared to venules decreased platelet adhesion and subsequently decreased the rate of thrombus formation in both WKY and SHR groups. However, the ratio of WKY to SHR platelet thrombus growth (platelet aggregation) time remained similar (0.83 +/- 0.06 in arterioles and 0.79 +/- 0.06 in venules). These results indicate that there is increased thrombus formation during hypertension and that the platelet adhesion processes may be of greater importance than platelet aggregation in producing this increase.

Increased erythrocyte aggregation in spontaneously hypertensive rats.

Alterations of red blood cell (RBC) aggregation and plasma viscosity are major contributors to the changes in blood rheologic properties that cause an increase in peripheral vascular resistance during the development of hypertension. Although basic research and clinical study have provided considerable understanding of the pathophysiology of hypertension, the objective of this study was to determine whether an increase in RBC aggregability and plasma viscosity precede or accompany the development of high arterial blood pressure. To address this question, RBC aggregation and plasma viscosity were studied in spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY) at 3 and 12 weeks of age. The plasma concentrations of fibrinogen and fibronectin (FN) were also analyzed in both age groups. RBC aggregability and plasma viscosity were increased in both young and mature SHR compared to age-matched normotensive WKY rats. Mean arterial blood pressure and diastolic pressures were increased in mature hypertensive rats, whereas in young SHR only diastolic pressure was elevated significantly. The concentration of fibrinogen was higher only in the mature hypertensive rats, whereas plasma FN content was greater in both 3- and 12-week-old SHR compared to age-matched WKY. These results show the existence of increased RBC aggregability and plasma hyperviscosity not only during the established phase of hypertension, but also during the early stage of hypertension development, when mean arterial blood pressure is not yet significantly elevated in the genetically hypertensive rat model. These changes may be related to significant increase in the plasma protein FN, which occurs at the same time as the RBC aggregability and plasma viscosity changes. These results may increase attention to changes in the rheologic properties and to the mechanisms involved in these processes in the early stages of hypertension development.

Spontaneously hypertensive rats are resistant to the development of hypercholesterolemia.

The arterioles of young spontaneously hypertensive rats (SHR) are purported to have an enhanced sensitivity to nitric oxide (NO)-dependent vasodilators, relative to normotensive animals, while NO-related arteriolar responses are diminished in both mature SHR as well as hypercholesterolemic normotensive rats. Because endothelial production of NO relaxes vascular smooth muscle and inhibits platelet adhesion and aggregation, hypercholesterolemia may synergistically affect the development of genetic hypertension. The NO-mediated baseline vascular tone, acetylcholine-induced dilation, and inhibition of platelet thrombus formation were studied over time (10 weeks) in SHR and hypercholesterolemic SHR (HC-SHR). The in vivo microcirculation of the cremaster muscle was used to quantitate all observations. The HC-SHR became significantly hypercholesterolemic after 1 week on the cholesterol-supplemented diet, with serum cholesterol concentrations remaining elevated for the 10 weeks studied. However, the serum cholesterol concentrations of HC-SHR were significantly less than those of Sprague-Dawley and Wistar-Kyoto rats fed the same diet. Dietary hypercholesterolemia did not exacerbate the development of genetic hypertension. Second- and third-order arterioles of SHR and age-matched HC-SHR constricted to the same extent when the NO synthase inhibitor N omega-nitro-L-arginine methyl ester (L-NAME) was applied. The third order arterioles of both groups also dilated the same amount to acetylcholine and sodium nitroprusside. Platelet thrombus formation induced by light/dye photochemistry was not different between the SHR and HC-SHR groups either at 1 or 10 weeks of diet, and L-NAME decreased the time to thrombus occlusion of blood flow equally in both groups. This is in marked contrast to the previously reported hypercholesterolemia-induced decreases in vascular reactivity in Sprague-Dawley rats. These current findings demonstrate that SHR are resistant to the development of hypercholesterolemia and that NO-mediated vascular responses in SHR are not attenuated by hypercholesterolemia.

Prostanoid antagonists inhibit the response of the microcirculation to "early" photodynamic therapy.

Microcirculatory shutdown appears to be of central importance in the mechanisms of action of photodynamic therapy (PDT). Traditionally 24-48 h are allowed between the administration of the photosensitizer and light to allow for tumor localization. However, previous studies have shown that the effects of PDT on the microcirculation are maximal soon after administration of the photosensitizer when serum levels are highest. This study involved the use of television video microscopy of the cremaster muscle microcirculation of male Sprague-Dawley rats to study the involvement of prostanoids in the effects of PDT on the microcirculation 30 min after administration of photofrin II. Pretreatment with topical indomethacin resulted in an altered response to PDT with arteriolar dilation and delay in vessel shutdown. The thromboxane A2 antagonist SQ29548 (100 mg/kg/min iv) resulted in a significant delay in platelet thrombus formation in arterioles and venules. These results indicate that prostanoids are involved in the mediation of the response of the normal microcirculation to PDT.

A comparison of the effects of photodynamic therapy on normal and tumor blood vessels in the rat microcirculation.

The effects of light activation of the tumor photosensitizer dihematoporphyrin ether (DHE) were studied in the microcirculation of the rat cremaster muscle. Arterioles and venules in an implanted chondrosarcoma were studied by in vivo television microscopy and were compared to normal vessels of the same size elsewhere in the preparation and in control preparations. Activation with green light (530-560 nm, 200 mW/cm2, 120 J/cm2) 48 h after intraperitoneal injection of DHE (10 mg/kg body wt) resulted in significant narrowing of diameters of red blood cell columns in tumor arterioles and venules. The response in normal and control arterioles and venules was not significantly different from that seen in the tumor vessels except that the control arterioles did not remain significantly constricted during the treatment period. Treatment resulted in stasis of blood flow in 90% of tumor and normal arterioles at the completion of light activation. In venules, stasis of blood flow was observed in 75% of tumor and 70% of normal vessels. Vasoconstriction was the primary response in arterioles, while thrombosis predominated in venules. Morphologic assessment of light-activated vessels in the cremaster preparation by transmission electron microscopy revealed platelet aggregation with damage to endothelial cells and smooth muscle cells. Perivascular effects observed included interstitial edema and damage to skeletal muscle cells. In the tumor-bearing preparation, no direct cytotoxic effect on the tumor cells was shown. The surrounding vessels exhibited similar vascular stasis, but the lining cells appeared minimally affected. Photoactivation of DHE results in significant changes in the microcirculation which lead to stasis of blood flow. In this model, the response was similar for the normal microvasculature and for the microcirculation of an implanted chondrosarcoma. These effects may account, in part, for the mechanism of action of photodynamic therapy.

Comparison of the effects of commonly used wound agents on epithelialization and neovascularization.

BACKGROUND: The primary effect sought with most topical wound therapy is antimicrobial. Topical wound agents are thought to promote normal healing by protecting the wound from infection. In this study, we examined the effect of six commonly used topical wound agents (bacitracin, sodium hypochlorite, silver nitrate, silver sulfadiazine, mafenide acetate, and povidone-iodine) on epithelialization and neovascularization in noninfected wounds. For this study, a new wound model was used in which direct visualization and quantification of wound epithelialization and neovascularization were carried out throughout the entire healing process. STUDY DESIGN: We measured the effect which 500 U per g of bacitracin, 0.25 percent of sodium hypochlorite, 0.5 percent silver nitrate, 1 percent silver sulfadiazine, 8.5 percent mafenide acetate, and 10 percent povodione-iodine had on the rate of wound epithelialization and neovascularization. The agents were applied topically to 99 circular full-thickness wounds (2.25 mm diameter, 0.125 mm depth) created on the dorsum of male hairless mouse ears. This model enabled us to visualize and measure directly wound epithelialization and neovascularization repeatedly throughout healing, using intravital video microscopy and computerized digitized planimetry. RESULTS: Control wounds and wounds treated with silver sulfadiazine (n = 18) and mafenide acetate (n = 14) epithelialized in 7.2 +/- 0.7, 7.1 +/- 0.3, and 7.3 +/- 0.3 days, respectively. This was significantly (p < 0.01) faster than the wounds treated with povidone-iodine (n = 10), sodium hypochlorite, (n = 8), and bacitracin (n = 13). Wounds treated with povidone-iodine epithelialized the slowest (11.8 +/- 0.55 days). Wound neovascularization was completed most rapidly in the groups treated with povidone-iodine and silver sulfadiazine (15.0 +/- 0.4 and 15.3 +/- 0.7 days, respectively). This was significantly (p < 0.05) faster than wounds treated with silver nitrate (n = 15), which neovascularized in 18.4 +/- 0.56 days. One-half of the wounds treated with sodium hypochlorite (eight of 16) did not epithelialize or neovascularize. CONCLUSIONS: The various antimicrobial agents studied in our in vivo model affect wound epithelialization and neovascularization differently. These effects on these two very important aspects of healing should be taken into consideration when indicating a specific agent for treatment of different types of wounds.

The microvascular effects of photodynamic therapy: evidence for a possible role of cyclooxygenase products.

Photodynamic therapy (PDT) of malignant tumours may involve the interruption of tumor and peritumor microcirculation. We have studied the effect of light activation of the photosensitizing drug dihematoporphyrin ether (DHE) on rat subcutaneous arterioles and the modulation of these effects by cyclooxygenase inhibitors indomethacin and acetyl salicylic acid (ASA). Animals received DHE 48 h prior to light activation and additionally either indomethacin, ASA or saline 3 h prior to treatment. Light activation (630 nm, 60 J/cm2) resulted in a significant reduction to 62 +/- 2% SEM of initial blood flow. This effect was inhibited by ASA (98 +/- 8% SEM) and indomethacin (87 +/- 8% SEM). Results from the administration of various doses of both compounds indicate that this inhibition is dose related. The data presented here show that PDT causes a significant reduction in blood flow in normal arterioles and that this effect was inhibited by ASA and indomethacin indicating that prostaglandins or thromboxane A2 may play an important role in the microvascular response to PDT.

The microphotohemolytic response of erythrocytes is altered by streptozotocin-induced diabetes and copper deficiency in rats.

Microphotohemolysis is a new technique that has been used to determine the presence of alterations in the erythrocyte membrane. The method involves light activation through a microscope of a fluorescent dye-erythrocyte-buffer solution in a hemocytometer. The interaction of the light and dye result in the generation of toxic oxygen products which attack the membrane allowing water to enter the cell. As hemolysis occurs the optical density of the microscopic field decreases and this is recorded for later quantitation with an image analysis system. Maximal effect, time to half maximal effect and the slope of the hemolysis curve are determined. The goal of this study was to determine if microphotohemolysis could be used to detect differences in erythrocytes from animals with altered physiological states such as hypercholesterolemia, diabetes, and copper deficiency. These are conditions that alter the lipid or protein structure of the erythrocyte membrane and/or the antioxidative capacity of the erythrocyte. There were no effects of hypercholesterolemia on the microphotohemolytic response of the erythrocyte. Streptozotocin-induced diabetes resulted in a decreased maximum effect, a significant shift of the hemolysis curve to the right (increased T 1/2) and a significant decrease in the slope of the hemolysis curve. Copper deficiency resulted in a significant decrease in the slope of the hemolysis curve. These results in diabetes and copper deficiency are consistent with an altered protein structure in the erythrocyte membrane that occurs in these conditions. The data demonstrate that this technique may be used to detect differences between normal and altered erythrocytes. As such, it could be useful in monitoring the course of a disease or its treatment.

Arteriolar dilation to endotoxin is increased in copper-deficient rats.

We have previously reported that there is an altered response to mast cell-mediated inflammation in copper-deficient rats. In the current study we determined the microvascular reactivity to inflammatory stimuli with lipopolysacccharide (LPS) during dietary copper restriction. Male Sprague-Dawley rats were fed purified diets which were either copper-adequate (CuA, 6 micrograms Cu/g) or copper-deficient (CuD, 0.4 micrograms Cu/g) for 4 weeks. Rats were anesthetized and the cremaster muscle was prepared for in vivo television microscopy. Arteriolar diameters were measured and then 2.5 mg/kg LPS was injected i.p. In separate groups, animals were pretreated with the NO-synthase inhibitor L-NAME (2 x 10(-4) M), the cyclooxygenase inhibitor ibuprofen (9.6 x 10(-5) M) or the histamine receptor antagonist diphenhydramine (DPH, 10(-6) M). LPS caused arteriolar dilation in both dietary groups with the response being significantly greater in the CuD group. Ibuprofen and DPH but not L-NAME, each significantly reduced but did not block the dilation in the CuD group. Ibuprofen and DPH together blocked the dilation. These results suggest that dietary copper deficiency increases arteriolar dilation to LPS. The mechanism appears to involve a greater response to arachidonic acid metabolites and histamine but not NO.

The influence of photodynamic therapy on the ultrastructure of the normal rat bladder.

Reduced bladder capacity is a major side effect for patients receiving photodynamic therapy (PDT) for bladder cancer. A rat bladder model has been developed to address both the vascular and tissue effects of the photodynamic treatment of the urinary bladder. Bladders were exteriorized and positioned in a plexiglass tissue bath. Effects on microvasculature were assessed during PDT of the bladder by recording luminal diameter changes in arterioles and venules. Animals receiving Photofrin II (10 mg kg-1) 30 min prior to PDT scored a statistically significant reduction in the diameter of the red blood cell column in the vessels, whereas administration of Photofrin II 48 h prior to PDT was ineffective. Morphological changes included significant endothelial and vascular myocyte damage in the 30 min PDT group alone. Among the other tissue components, the mucosal lining was minimally affected and the response of the muscularis was highly variable. Smooth muscle cell changes ranged from mild contraction to frank necrosis with many of the affected cells located near the altered vascular beds. These data suggest that the clinical symptoms of reduced bladder capacity can be accounted for by vascular damage and myocyte sensitivity. Further refinements in the Photofrin II and light doses used in therapy may reduce bladder complications and allow for better management of bladder cancer.

The effect of severe burn injury on proinflammatory cytokines and leukocyte behavior: its modulation with granulocyte colony-stimulating factor.

Severe injury causes immunosuppression. The main contributors are impaired leukocyte function and a cytokine dysbalance. GCSF increases PMN count, function and modulates the inflammatory response. However GCSF may overactivate leukocytes. The purpose of this study is to investigate whether GCSF is able to restore immune competence after severe injury. Lewis rats were divided into three groups: 30% TBSA burn + vehicle; 30% TBSA burn + GCSF (150 microg rhGCSF); Control. Blood samples were taken for total white cell count, PMNs, TNFalpha and IFNgamma. Leukocyte rolling and sticking were measured in the cremaster muscle microcirculation. Leukocyte diapedesis was investigated by lavage of the abdominal cavity and the lungs. Total white cell and PMN counts in the burn + GCSF group were significantly higher (P<0.001) than in burn+vehicle animals. Leukocyte adherence and diapedesis were not elevated in the burn + GCSF group as compared to the burn + vehicle group. TNFalpha (P<0.05) and IFNgamma (P<0.001) levels were significantly increased in the burn + vehicle animals compared to the burn + GCSF animals. GCSF modifies the immune system, as shown by an increase in white cell and PMN counts and by balancing the overall immune response from proinflammatory to normal, as shown by decreased TNFalpha and IFNgamma levels. GCSF does not overactivate PMNs.

Augmentation of skeletal muscle flap survival using platelet derived growth factor.

Distal muscle flap ischemia and necrosis is a recognized complication of acute elevation of large skeletal muscle flaps. The aim of this study was to investigate whether the angiogenic properties of platelet derived growth factor (PDGF) could be used to augment skeletal muscle flap survival through the induction of new blood vessel formation before flap elevation. We compared this form of flap augmentation with that achieved by subjecting the muscle to a bipedicled vascular delay procedure. The animal model used was the latissimus dorsi muscle of the male homozygous (hr/hr) hairless mouse. Four groups of animals were investigated in this study (n = 10 per group). Group 1 was the control group in which the entire muscle was elevated as a thoracodorsally based island flap. In group 2, the muscle was subjected to a bipedicled vascular delay procedure. In group 3, the muscle was treated with 500 microg of recombinant human platelet derived growth factor BB. In group 4, the muscle was treated with placebo. Ten days later the entire latissimus dorsi muscle was elevated as a thoracodorsally based island flap in groups 2, 3, and 4. Percentage muscle flap survival was quantitated in all groups 5 days after elevation of the entire muscle. Angiogenesis was then quantitated by analyzing capillary to muscle fiber ratios after alkaline phosphatase staining of representative latissimus dorsi muscle samples from the proximal, middle, and distal flap segments. Percentage muscle flap survival was significantly better in PDGF treated muscles when compared with the vascularly delayed muscles (p < 0.001). Histologic analysis of latissimus dorsi muscle flaps demonstrated a significantly greater number of capillaries in the middle (p < 0.001) and distal (p < 0.001) flap segments of PDGF-treated flaps when compared with the vascularly delayed flaps. Treatment of skeletal muscle with PDGF before flap creation resulted in survival of the entire muscle flap. Our results suggest that this survival may be secondary to PDGF-induced angiogenesis.

Effect of low dose aspirin on thrombus formation at arterial and venous microanastomoses and on the tissue microcirculation.

In free flap/replantation surgery, failure is usually associated with thrombotic occlusion of a microvascular anastomosis (risk zone I) or, on occasion, flow impairment in the microcirculation of the transferred or replanted tissue (risk zone II). The objective of this study is to describe the effect of low dose aspirin on blood flow at both risk zones in microvascular surgery. Risk zone I: In rat femoral arteries and veins, thrombus formation was measured at the anastomoses using transillumination and videomicroscopy. Forty male Wistar rats were assigned in equal numbers to four groups: either arterial or venous injury with either aspirin (5 mg/kg systemically) or saline treatment. We found that aspirin significantly reduces thrombus formation at the venous anastomosis (p = 0.001). Risk zone II: In the isolated rat cremaster muscle downstream from an arterial anastomosis, we measured capillary perfusion, arteriolar diameters, and the appearance of platelet emboli for 6 hours in the muscle microcirculation. Sixteen male Wistar rats in two equal groups received either aspirin (5 mg/kg systemically) or saline. We found that in aspirin-treated animals, capillary perfusion is significantly (p = 0.002) improved, whereas arteriolar diameters and emboli only slightly increased. In conclusion, low dose aspirin inhibits anastomotic venous thrombosis and improves microcirculatory perfusion in our rat model. These studies provide quantitative data confirming and clarifying the beneficial effects of low dose aspirin in microvascular surgery.

Cardiovascular effects of dietary copper deficiency.

Dietary copper deficiency may impair cardiovascular health by contributing to high blood pressure, enhancement of inflammation, anemia, reduced blood clotting and arteriosclerosis. The purpose of this review is to compile information on the numerous changes of the heart, blood and blood vessels that may contribute to these cardiovascular defects. These alterations include weakened structural integrity of the heart and blood vessels, impairment of the use of energy by the heart, reduced ability of the heart to contract, altered ability of blood vessels to control their diameter and to grow, and altered structure and function of circulating blood cells. The fundamental causes of these changes rest largely on reduced effectiveness of enzymes that depend on copper for their activity.

Relationship between dietary copper concentration and acetylcholine-induced vasodilation in the microcirculation of rats.

Dietary copper deficiency has been shown to significantly reduce acetylcholine (Ach)-induced vascular smooth muscle relaxation. The current study was designed to examine the relative relationship between dietary copper and the vasodilator response to Ach in the microcirculation of the rat. Male weanling rats were fed a purified basal diet supplemented with 6.0, 3.0, 1.5 or 0.0 microg Cu/g diet for 4 weeks to provide an adequate, two marginal, and deficient intakes of dietary copper. Arteriole dilation in response to increasing concentrations of acetylcholine (10(-7) to 10(-4) M) was measured in the in vivo cremaster muscle microcirculation for each dietary group. Liver copper and both aortic and erythrocyte Cu,Zn-SOD activity were used as indices of systemic copper status. Dilation to the increasing concentrations of Ach was only different in the 0 microg Cu supplemented group compared to the copper-adequate control values. However, the combined results showed an exponential increase in 10(-5) M Ach-induced vasodilation as liver copper concentration increases from 0 microg Cu/g dry wt. This relationship suggests that dilation is attenuated at liver Cu concentrations below 5 microg/g dry wt. The results indicate that Ach-induced vasodilation is copper-dependent but that the pathway is not very sensitive to short-term marginal restriction of copper intake.