Heterogeneity in endothelium-derived nitric oxide-mediated relaxation of different sized pulmonary arteries of newborn lambs.

Endothelium-derived nitric oxide (EDNO) plays a pivotal role in regulating pulmonary circulation. To determine whether there is a heterogeneity in EDNO-mediated responses of different sized pulmonary vessels, we studied small and large isolated pulmonary arteries of newborn lambs (diameter, 0.4-0.7 and 1.5-2.5 mm, respectively). The isometric tension of vessel rings were recorded while suspended in organ chambers filled with modified Krebs-Ringer bicarbonate solution (95% O2-5% CO2, 37 degrees C). In vessels preconstricted with norepinephrine, acetylcholine and bradykinin induced a greater relaxation of small pulmonary arteries than of large pulmonary arteries. Acetylcholine, bradykinin, and nitric oxide also induced a greater increase in cGMP content in small arteries than in large ones. The responses to acetylcholine and bradykinin were endothelium-dependent and inhibited by nitro-L-arginine, an inhibitor of nitric oxide synthase. In vessels without endothelium, the response to nitric oxide was inhibited by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, an inhibitor of soluble guanylate cyclase. The activity of soluble guanylyl cyclase of small arteries was greater than that of large arteries under basal conditions and after stimulation with S-nitroso-N-acetylpenicillamine, a nitric oxide donor. These results demonstrate that heterogeneity exists in EDNO-mediated relaxation of small and large pulmonary arteries in newborn lambs. A difference in the soluble guanylate cyclase activity of vascular smooth muscle may have contributed to this phenomenon.

Vasopressin dilates the rat carotid artery by stimulating V1 receptors.

The acute effects of various vasopressor agents on the diameter of the common carotid artery were studied in halothane-anesthetized normotensive rats. The animals were infused intravenously for 60 min with equipressor doses of angiotensin II (10 ng/min), the alpha1-stimulant methoxamine (5 microg/min), lysine vasopressin (5 mU/min), or vehicle. The arterial diameter was measured by using a high-resolution ultrasonic echo-tracking device. The three vasoconstrictors increased the carotid artery diameter, but this effect was significantly more pronounced with lysine vasopressin. Even a nonpressor dose of lysine vasopressin (1 mU/min) caused a significant increase in the arterial diameter. The lysine vasopressin-induced vasodilatation could be prevented by the administration of d(CH2)5Tyr(Me)AVP (10 microg, i.v.), a selective V1-vasopressinergic receptor antagonist. These data therefore suggest that a short-term increase in blood pressure induces in rats a distention of the carotid artery. The increase in arterial diameter seems to involve an active mechanism with lysine vasopressin caused by the stimulation of V1-vasopressinergic receptors.

Repeated Double-Poling Sprint Training in Hypoxia by Competitive Cross-country Skiers.

PURPOSE: Repeated-sprint training in hypoxia (RSH) was recently shown to improve repeated-sprint ability (RSA) in cycling. This phenomenon is likely to reflect fiber type-dependent, compensatory vasodilation, and therefore, our hypothesis was that RSH is even more beneficial for activities involving upper body muscles, such as double poling during cross-country skiing. METHODS: In a double-blinded fashion, 17 competitive cross-country skiers performed six sessions of repeated sprints (each consisting of four sets of five 10-s sprints, with 20-s intervals of recovery) either in normoxia (RSN, 300 m; FiO2, 20.9%; n = 8) or normobaric hypoxia (RSH, 3000 m; FiO2, 13.8 %; n = 9). Before (pre) and after (post) training, performance was evaluated with an RSA test (10-s all-out sprints-20-s recovery, until peak power output declined by 30%) and a simulated team sprint (team sprint, 3 × 3-min all-out with 3-min rest) on a double-poling ergometer. Triceps brachii oxygenation was measured by near-infrared spectroscopy. RESULTS: From pretraining to posttraining, peak power output in the RSA was increased (P < 0.01) to the same extent (29% ± 13% vs 26% ± 18%, nonsignificant) in RSH and in RSN whereas the number of sprints performed was enhanced in RSH (10.9 ± 5.2 vs 17.1 ± 6.8, P < 0.01) but not in RSN (11.6 ± 5.3 vs 11.7 ± 4.3, nonsignificant). In addition, the amplitude in total hemoglobin variations during sprints throughout RSA rose more in RSH (P < 0.01). Similarly, the average power output during all team sprints improved by 11% ± 9% in RSH and 15% ± 7% in RSN. CONCLUSIONS: Our findings reveal greater improvement in the performance of repeated double-poling sprints, together with larger variations in the perfusion of upper body muscles in RSH compared with those in RSN.

Noninvasive visualization of coronary artery endothelial function in healthy subjects and in patients with coronary artery disease.

OBJECTIVES: The goal was to test 2 hypotheses: first, that coronary endothelial function can be measured noninvasively and abnormal function detected using clinical 3.0-T magnetic resonance imaging (MRI); and second, that the extent of local coronary artery disease (CAD), in a given patient, is related to the degree of local abnormal coronary endothelial function. BACKGROUND: Abnormal endothelial function mediates the initiation and progression of atherosclerosis and predicts cardiovascular events. However, direct measures of coronary endothelial function have required invasive assessment. METHODS: The MRI was performed in 20 healthy adults and 17 patients with CAD. Cross-sectional coronary area and blood flow were quantified before and during isometric handgrip exercise, an endothelial-dependent stressor. In 10 severe, single-vessel CAD patients, paired endothelial function was measured in the artery with severe stenosis and the contralateral artery with minimal disease. RESULTS: In healthy adults, coronary arteries dilated and flow increased with stress. In CAD patients, coronary artery area and blood flow decreased with stress (both p </= 0.02). In the paired study, coronary artery area and blood flow failed to increase during exercise in the mildly diseased vessel, but both area (p = 0.01) and blood flow (p = 0.02) decreased significantly in the severely diseased, contralateral artery. CONCLUSIONS: Endothelial-dependent coronary artery dilation and increased blood flow in healthy subjects, and their absence in CAD patients, can now be directly visualized and quantified noninvasively. Local coronary endothelial function differs between severely and mildly diseased arteries in a given CAD patient. This novel, safe method may offer new insights regarding the importance of local coronary endothelial function and improved risk stratification in patients at risk for and with known CAD.

Endothelial dysfunction in systemic lupus erythematosus: evaluation with 13N-ammonia PET.

Systemic lupus erythematosus (SLE) affects multiple organs and systems, severely involving the cardiovascular system. The aim of this study was to evaluate the presence of endothelial dysfunction with N-13-ammonia PET in asymptomatic SLE patients. Methods: We enrolled 16 women with SLE and 16 healthy women. Myocardial blood flow (MBF) was quantified in a 64-slice PET/CT scanner at rest, during a cold pressor test (CPT), and during stress. Endothelium-dependent vasodilation index, %Delta MBF, and myocardial flow reserve (MFR) were calculated. Results: There were 16 women in the SLE group (mean age +/- SD, 31.4 +/- 8.3 y) and 16 women in the healthy control group (31.5 +/- 11.1 y). Mean endothelium-dependent vasodilatation index and %Delta MBF were significantly lower in SLE patients (1.18 +/- 0.55 vs. 1.63 +/- 0.65, P = 0.04, and 18 +/- 55 vs. 63 +/- 65, P = 0.04, respectively). MFR was also lower in the SLE group (2.41 +/- 0.59 vs. 2.73 +/- 0.77, P = 0.20). Conclusion: SLE patients who are free of active disease present abnormal coronary flow and endothelial dysfunction. It is necessary to develop and intensify treatment strategies directed to CAD in SLE patients.

The sand rat, Psammomys obesus, develops type 2 diabetic retinopathy similar to humans.

PURPOSE: Diabetic retinopathy (DR) is a leading cause of blindness, yet pertinent animal models are uncommon. The sand rat (Psammomys obesus), exhibiting diet-induced metabolic syndrome, might constitute a relevant model. METHODS: Adult P. obesus (n = 39) were maintained in captivity for 4 to 7 months and fed either vegetation-based diets (n = 13) or standard rat chow (n = 26). Although plant-fed animals exhibited uniform body weight and blood glucose levels over time, nearly 60% of rat chow-raised animals developed diabetes-like symptoms (test group). Animals were killed, and their eyes and vitreous were processed for immunochemistry. RESULTS: Compared with plant-fed animals, diabetic animals showed many abnormal vascular features, including vasodilation, tortuosity, and pericyte loss within the blood vessels, hyperproteinemia and elevated ratios of proangiogenic and antiangiogenic growth factors in the vitreous, and blood-retinal barrier breakdown. Furthermore, there were statistically significant decreases in retinal cell layer thicknesses and densities, accompanied by profound alterations in glia (downregulation of glutamine synthetase, glutamate-aspartate transporter, upregulation of glial fibrillar acidic protein) and many neurons (reduced expression of protein kinase Cα and Cξ in bipolar cells, axonal degeneration in ganglion cells). Cone photoreceptors were particularly affected, with reduced expression of short- and mid-/long-wavelength opsins. Hypercaloric diet nondiabetic animals showed intermediate values. CONCLUSIONS: Simple dietary modulation of P. obesus induces a rapid and severe phenotype closely resembling human type 2 DR. This species presents a valuable novel experimental model for probing the neural (especially cone photoreceptor) pathogenic modifications that are difficult to study in humans and for screening therapeutic strategies.

Melatonin improves glucose homeostasis and endothelial vascular function in high-fat diet-fed insulin-resistant mice.

Obesity and insulin resistance represent a problem of utmost clinical significance worldwide. Insulin-resistant states are characterized by the inability of insulin to induce proper signal transduction leading to defective glucose uptake in skeletal muscle tissue and impaired insulin-induced vasodilation. In various pathophysiological models, melatonin interacts with crucial molecules of the insulin signaling pathway, but its effects on glucose homeostasis are not known. In a diet-induced mouse model of insulin resistance and normal chow-fed control mice, we sought to assess the effects of an 8-wk oral treatment with melatonin on insulin and glucose tolerance and to understand underlying mechanisms. In high-fat diet-fed mice, but not in normal chow-fed control mice, melatonin significantly improved insulin sensitivity and glucose tolerance, as evidenced by a higher rate of glucose infusion to maintain euglycemia during hyperinsulinemic clamp studies and an attenuated hyperglycemic response to an ip glucose challenge. Regarding underlying mechanisms, we found that melatonin restored insulin-induced vasodilation to skeletal muscle, a major site of glucose utilization. This was due, at least in part, to the improvement of insulin signal transduction in the vasculature, as evidenced by increased insulin-induced phosphorylation of Akt and endoethelial nitric oxide synthase in aortas harvested from melatonin-treated high-fat diet-fed mice. In contrast, melatonin had no effect on the ability of insulin to promote glucose uptake in skeletal muscle tissue in vitro. These data demonstrate for the first time that in a diet-induced rodent model of insulin resistance, melatonin improves glucose homeostasis by restoring the vascular action of insulin.

Elevated endocannabinoid plasma levels are associated with coronary circulatory dysfunction in obesity.

AIMS: Aim of this study was to evaluate a possible association between endocannabinoid (EC) plasma levels, such as anandamide (AEA) and 2-arachidonoylglycerol (2-AG), and coronary circulatory function in obesity. METHODS AND RESULTS: Myocardial blood flow (MBF) responses to cold pressor test (CPT) and during pharmacological vasodilation with dipyridamole were measured with (13)N-ammonia PET/CT. Study participants (n = 77) were divided into three groups based on their body mass index (BMI, kg/m(2)): control group 20 ≤ BMI <25 (n = 21); overweight group, 25 ≤ BMI <30 (n = 26); and obese group, BMI ≥ 30 (n = 30). Anandamide plasma levels, but not 2-AG plasma levels, were significantly elevated in obesity as compared with controls, respectively [0.68 (0.53, 0.78) vs. 0.56 (0.47, 0.66) ng/mL, P = 0.020, and 2.2 (1.21, 4.59) vs. 2.0 (0.80, 5.90) ng/mL, P = 0.806)]. The endothelium-related change in MBF during CPT from rest (ΔMBF) progressively declined in overweight and obese when compared with control group [0.21 (0.10, 0.27) and 0.09 (-0.01, 0.15) vs. 0.26 (0.23, 0.39) mL/g/min; P = 0.010 and P = 0.0001, respectively). Compared with controls, hyperaemic MBFs were significantly lower in overweight and obese individuals [2.39 (1.97, 2.62) vs. 1.98 (1.69, 2.26) and 2.10 (1.76, 2.36); P = 0.007 and P = 0.042, respectively)]. In obese individuals, AEA and 2-AG plasma levels were inversely correlated with ΔMBF to CPT (r = -0.37, P = 0.046 and r = -0.48, P = 0.008) and hyperaemic MBFs (r = -0.38, P = 0.052 and r = -0.45, P = 0.017), respectively. CONCLUSIONS: Increased EC plasma levels of AEA and 2-AG are associated with coronary circulatory dysfunction in obese individuals. This observation might suggest increases in EC plasma levels as a novel endogenous cardiovascular risk factor in obesity, but needing further investigations.

Effects of adrenergic and cholinergic blockade on insulin-induced stimulation of calf blood flow in humans.

Euglycemic hyperinsulinemia stimulates both sympathetic nerve activity and blood flow to skeletal muscle, but the mechanism is unknown. Possible mechanisms that may stimulate muscle blood flow include neural, humoral, or metabolic effects of insulin. To determine whether such insulin-induced vasodilation is modulated by stimulation of adrenergic or cholinergic mechanisms, we obtained, in eight healthy lean subjects, plethysmographic measurements of calf blood flow during 3 h of hyperinsulinemic (1 mU.kg-1.min-1) euglycemic clamp performed alone or during concomitant beta-adrenergic (propranolol infusion), cholinergic (atropine infusion), or alpha-adrenergic (prazosin administration) blockade. Euglycemic hyperinsulinemia alone increased calf blood flow by 38 +/- 10% (means +/- SE) and decreased vascular resistance by 27 +/- 4% (P < 0.01). The principal new observation is that these insulin-induced vasodilatory responses were not attenuated by concomitant propranolol or atropine infusion, nor were they potentiated by prazosin administration. In conclusion, these findings provide evidence that during euglycemic hyperinsulinemia in lean healthy humans stimulation of muscle blood flow is not mediated primarily by beta-adrenergic or cholinergic mechanisms. Furthermore, alpha-adrenergic mechanisms do not markedly limit insulin-induced stimulation of muscle blood flow.

Developmental change in isoproterenol-mediated relaxation of pulmonary veins of fetal and newborn lambs.

beta-Adrenergic agonists are important regulators of perinatal pulmonary circulation. They cause vasodilation primarily via the adenyl cyclase-adenosine 3',5'-cyclic monophosphate (cAMP) pathway. We examined the responses of isolated fourth-generation pulmonary veins of term fetal (145 +/- 2 days gestation) and newborn (10 +/- 1 days) lambs to isoproterenol, a beta-adrenergic agonist. In vessels preconstricted with U-46619 (a thromboxane A2 analog), isoproterenol induced greater relaxation in pulmonary veins of newborn lambs than in those of fetal lambs. The relaxation was eliminated by propranolol, a beta-adrenergic antagonist. Forskolin, an activator of adenyl cyclase, also caused greater relaxation of veins of newborn than those of fetal lambs. 8-Bromoadenosine 3',5'-cyclic monophosphate, a cell membrane-permeable analog of cAMP, induced a similar relaxation of all vessels. Biochemical studies show that isoproterenol and forskolin induced a greater increase in cAMP content and in adenyl cyclase activity of pulmonary veins in the newborn than in the fetal lamb. These results demonstrate that beta-adrenergic-agonist-mediated relaxation of pulmonary veins increases with maturation. An increase in the activity of adenyl cyclase may contribute to the change.

Nitric oxide activity through guanylate cyclase and phosphodiesterase modulation is impaired in fetal lambs with congenital diaphragmatic hernia.

BACKGROUND: Congenital diaphragmatic hernia (CDH) is associated with pulmonary hypertension and death. Administration of nitric oxide (NO) alone remains ineffective in CDH cases. We investigated in near full-term lambs with and without CDH the role of guanylate cyclase (GC), the enzyme activated by NO in increasing cyclic 3'-5'-guanylosine monophosphate, and the role of phosphodiesterase (PDE) 5, the enzyme-degrading cyclic 3'-5'-guanylosine monophosphate. METHODS: Congenital diaphragmatic hernia was surgically created in fetal lambs at 85 days of gestation. Pulmonary hemodynamics were assessed by means of pressure and blood flow catheters (135 days). In vitro, we tested drugs on rings of isolated pulmonary vessels. RESULTS: In vivo, sodium nitroprusside, a direct NO donor, and methyl-2(4-aminophenyl)-1,2-dihydro-1-oxo-7-(2-pyridinylmethoxy)-4-(3,4,5 trimethoxyphenyl)-3-isoquinoline carboxylate sulfate (T-1032) and Zaprinast, both PDE 5 blockers, reduced pulmonary vascular resistance in CDH and non-CDH animals. The activation of GC by sodium nitroprusside and the inhibition of PDE 5 by T-1032 were less effective in CDH animals. In vitro, the stimulation of GC by 3(5'hydroxymethyl-2'furyl)-1-benzyl indazole (YC-1) (a benzyl indazole derivative) and the inhibition of PDE 5 by T-1032 were less effective in pulmonary vascular rings from CDH animals. The YC-1-induced vasodilation in rings from CDH animals was higher when associated with the PDE 5 inhibitor T-1032. CONCLUSIONS: Guanylate cyclase and PDE 5 play a role in controlling pulmonary vascular tone in fetal lambs with or without CDH. Both enzymes seem to be impaired in fetal lambs with CDH.

Angiotensin-converting enzyme inhibition improves vascular function in rheumatoid arthritis.

BACKGROUND: The excess in cardiovascular risk in patients with rheumatoid arthritis provides a strong rationale for early therapeutical interventions. In view of the similarities between atherosclerosis and rheumatoid arthritis and the proven benefit of angiotensin-converting enzyme inhibitors in atherosclerotic vascular disease, it was the aim of the present study to delineate the impact of ramipril on endothelial function as well as on markers of inflammation and oxidative stress in patients with rheumatoid arthritis. METHODS AND RESULTS: Eleven patients with rheumatoid arthritis were included in this randomized, double-blind, crossover study to receive ramipril in an uptitration design (2.5 to 10 mg) for 8 weeks followed by placebo, or vice versa, on top of standard antiinflammatory therapy. Endothelial function assessed by flow-mediated dilation of the brachial artery, markers of inflammation and oxidative stress, and disease activity were investigated at baseline and after each treatment period. Endothelial function assessed by flow-mediated dilation increased from 2.85+/-1.49% to 4.00+/-1.81% (P=0.017) after 8 weeks of therapy with ramipril but did not change with placebo (from 2.85+/-1.49% to 2.84+/-2.47%; P=0.88). Although systolic blood pressure and heart rate remained unaltered, diastolic blood pressure decreased slightly from 78+/-7 to 74+/-6 mm Hg (P=0.03). Tumor necrosis factor-alpha showed a significant inverse correlation with flow-mediated dilation (r=-0.408, P=0.02), and CD40 significantly decreased after ramipril therapy (P=0.049). CONCLUSIONS: Angiotensin-converting enzyme inhibition with 10 mg/d ramipril for 8 weeks on top of current antiinflammatory treatment markedly improved endothelial function in patients with rheumatoid arthritis. This finding suggests that angiotensin-converting enzyme inhibition may provide a novel strategy to prevent cardiovascular events in these patients.

Role of atrial natriuretic peptides and neuropeptide Y in blood pressure regulation.

Atrial natriuretic peptides (ANP) are released into the circulation in response to enhanced atrial stretching. These peptides not only have diuretic and natriuretic properties, but also exert a relaxing effect on the vasculature. Moreover, they antagonize the contractions induced by norepinephrine and angiotensin II. Neuropeptide Y (NPY) is also a vasoactive peptide. It is widely distributed throughout the central and peripheral nervous systems. NPY is coreleased with norepinephrine by perivascular nerve endings. At high concentrations, this peptide has a direct vasoconstrictor effect. In addition, it enhances the vascular effect of various agonists, including norepinephrine and angiotensin II. Both ANP and NPY have an inhibitory effect on renin secretion. This effect may have important implications for the role of these peptides in cardiovascular regulation.

Effects of long-term estrogen replacement therapy in postmenopausal women with coronary risk factors

Objective: Hormone replacement therapy (HRT) with estrogen alone or in concert with progesterone may exert beneficial effects on coronary endothelium-dependent vasomotion in postmenopausal women without traditional coronary risk factors. We aimed to evaluate the effect of HRT on coronary vasomotor function in postmenopausal women with traditional coronary risk factors such as hypertension, hypercholesterolemia and smoking as compared to those without HRT. Methods: Combining N-13 ammonia with PET, myocardial blood flow (MBF) was measured in ml/g/min at rest, during cold pressor test (CPT, reflecting predominantly endothelium-dependent vasomotion)and during pharmacologic vasodilation (representing predominantly endothelium-independent vasomotion) in 48 postmenopausal women with various coronary risk factors during a mean follow up (FU) of 20_9 months. postmenopausal women wer grouped according to HRT: group 1 with HRT (n_18), group 2 without HRT (n_18) and group 3 with HRT at baseline but not at FU (n_12). Results: during FU, HRT did not significantly affect lipid profile and plasma glucose levels. At baseline resting MBF was similar between groups (Table).After the FU, in group 2 and 3 the endothelium-related increase in MBF from rest to CPT (_ MBF) was significantly less than at baseline (*p_0.05) (Table). Conversely, in group 1 _MBF to CPT at FU was not significantly different from the baseline study. The group comparison of CPT-induced _MBF in group 2 and group 3 after the FU period was significantly different from group 1 (p_0.006 by ANOVA). Finally, in all three groups, hyperemic MBFs during pharmacologic vasodilation did not differ significantly between baseline and FU (Table). Conclusion: In postmenopausal women with coronary risk factors, HRT may counterbalance the adverse effects of traditional coronary risk factors on endothelium-dependent coronary vasomotion. Consequently, in addition to standard management of coronary risk factors, HRT may exert beneficial effects on the coronary endothelium that may delay the progression of coronary artery disease in postmenopausal women.

Systemic and pulmonary vascular dysfunction in children conceived by assisted reproductive technologies.

BACKGROUND: Assisted reproductive technology (ART) involves the manipulation of early embryos at a time when they may be particularly vulnerable to external disturbances. Environmental influences during the embryonic and fetal development influence the individual's susceptibility to cardiovascular disease, raising concerns about the potential consequences of ART on the long-term health of the offspring. METHODS AND RESULTS: We assessed systemic (flow-mediated dilation of the brachial artery, pulse-wave velocity, and carotid intima-media thickness) and pulmonary (pulmonary artery pressure at high altitude by Doppler echocardiography) vascular function in 65 healthy children born after ART and 57 control children. Flow-mediated dilation of the brachial artery was 25% smaller in ART than in control children (6.7±1.6% versus 8.6±1.7%; P<0.0001), whereas endothelium-independent vasodilation was similar in the 2 groups. Carotid-femoral pulse-wave velocity was significantly (P<0.001) faster and carotid intima-media thickness was significantly (P<0.0001) greater in children conceived by ART than in control children. The systolic pulmonary artery pressure at high altitude (3450 m) was 30% higher (P<0.001) in ART than in control children. Vascular function was normal in children conceived naturally during hormonal stimulation of ovulation and in siblings of ART children who were conceived naturally. CONCLUSIONS: Healthy children conceived by ART display generalized vascular dysfunction. This problem does not appear to be related to parental factors but to the ART procedure itself. CLINICAL TRIAL REGISTRATION: URL: www.clinicaltrials.gov. Unique identifier: NCT00837642.