Simultaneous hybrid repair of symptomatic femoral, iliac, and abdominal aortic aneurysms.

BACKGROUND: Focal peripheral arterial aneurysms, though rare, have a relatively high association with coexisting synchronous or metachronous aneurysms. While most are asymptomatic at presentation, there is concern for aneurysm thrombosis, embolization, or rupture, which can lead to acute limb ischemia or even limb loss. These complications require early intervention with either open or endovascular surgery, oftentimes staged due to complexity. METHOD: We describe a case of a 65-year-old male presenting with a symptomatic common femoral artery aneurysm with a simultaneous infrarenal abdominal aortic aneurysm, requiring a hybrid endovascular and open approach for operative repair due to the size and characteristics of his aneurysms. DISCUSSION: As the consensus for the management of synchronous/metachronous aneurysms is to stage the procedures, it is important to report scenarios where a single hybrid operation was technically feasible and resulted in good patient outcomes. CONCLUSION: This report supports the role of utilizing multiple hybrid operative techniques to best repair the respective aneurysm in a single operation, with favorable patient outcomes.

Phylogenomics resolves major relationships and reveals significant diversification rate shifts in the evolution of silk moths and relatives.

BACKGROUND: Silkmoths and their relatives constitute the ecologically and taxonomically diverse superfamily Bombycoidea, which includes some of the most charismatic species of Lepidoptera. Despite displaying spectacular forms and diverse ecological traits, relatively little attention has been given to understanding their evolution and drivers of their diversity. To begin to address this problem, we created a new Bombycoidea-specific Anchored Hybrid Enrichment (AHE) probe set and sampled up to 571 loci for 117 taxa across all major lineages of the Bombycoidea, with a newly developed DNA extraction protocol that allows Lepidoptera specimens to be readily sequenced from pinned natural history collections. RESULTS: The well-supported tree was overall consistent with prior morphological and molecular studies, although some taxa were misplaced. The bombycid Arotros Schaus was formally transferred to Apatelodidae. We identified important evolutionary patterns (e.g., morphology, biogeography, and differences in speciation and extinction), and our analysis of diversification rates highlights the stark increases that exist within the Sphingidae (hawkmoths) and Saturniidae (wild silkmoths). CONCLUSIONS: Our study establishes a backbone for future evolutionary, comparative, and taxonomic studies of Bombycoidea. We postulate that the rate shifts identified are due to the well-documented bat-moth "arms race". Our research highlights the flexibility of AHE to generate genomic data from a wide range of museum specimens, both age and preservation method, and will allow researchers to tap into the wealth of biological data residing in natural history collections around the globe.

Clinicopathologic characteristics associated with long-term survival in advanced epithelial ovarian cancer: an NRG Oncology/Gynecologic Oncology Group ancillary data study.

OBJECTIVE: To identify clinicopathologic factors associated with 10-year overall survival in epithelial ovarian cancer (EOC) and primary peritoneal cancer (PPC), and to develop a predictive model identifying long-term survivors. METHODS: Demographic, surgical, and clinicopathologic data were abstracted from GOG 182 records. The association between clinical variables and long-term survival (LTS) (>10years) was assessed using multivariable regression analysis. Bootstrap methods were used to develop predictive models from known prognostic clinical factors and predictive accuracy was quantified using optimism-adjusted area under the receiver operating characteristic curve (AUC). RESULTS: The analysis dataset included 3010 evaluable patients, of whom 195 survived greater than ten years. These patients were more likely to have better performance status, endometrioid histology, stage III (rather than stage IV) disease, absence of ascites, less extensive preoperative disease distribution, microscopic disease residual following cyoreduction (R0), and decreased complexity of surgery (p<0.01). Multivariable regression analysis revealed that lower CA-125 levels, absence of ascites, stage, and R0 were significant independent predictors of LTS. A predictive model created using these variables had an AUC=0.729, which outperformed any of the individual predictors. CONCLUSIONS: The absence of ascites, a low CA-125, stage, and R0 at the time of cytoreduction are factors associated with LTS when controlling for other confounders. An extensively annotated clinicopathologic prediction model for LTS fell short of clinical utility suggesting that prognostic molecular profiles are needed to better predict which patients are likely to be long-term survivors.

Identification of candidate circulating cisplatin-resistant biomarkers from epithelial ovarian carcinoma cell secretomes.

BACKGROUND: The majority of patients diagnosed with advanced epithelial ovarian carcinoma (EOC) relapse with resistant disease, and there are no biomarkers that possess clinical utility to identify or monitor these patients. This study aimed to identify secreted proteins ('secretome') collected from human EOC cell lines that differ in their inherent platinum sensitivity. METHODS: Secreted proteins collected from conditioned medium from ovarian cancer cell lines that vary in their sensitivity to cisplatin were digested with trypsin and analysed by liquid chromatography-tandem mass spectrometry for peptide identification. RESULTS: Of the 1688 proteins identified, 16 possessed significant differential abundances (P<0.05) between the platinum-resistant and -sensitive cell lines. A number of these were verified by immunoblot, including COL11A1, which was also found to be associated with worse progression-free survival (PFS; N=723) and overall survival (OS; N=1183) as assessed from publicly available transcript expression data from ovarian cancer tumour specimens. CONCLUSION: Secretome proteomics of EOC cells resulted in the identification of a novel candidate biomarker, COL11A1. The expression level of COL11A1 correlates to worse PFS and OS, and is predicted to reside in peripheral circulation making this an attractive candidate for validation in sera as a biomarker of cisplatin resistance and poor outcome.

Investigation into the sources of superoxide in human blood vessels: angiotensin II increases superoxide production in human internal mammary arteries.

BACKGROUND: Increased vascular superoxide anion (.O(2)(-)) production contributes to endothelial dysfunction and hypertension in animal models of cardiovascular disease. Observations in experimental animals suggest that angiotensin II (Ang II) increases.O(2)(-) production by activation of vascular NAD(P)H oxidase. We studied the sources of.O(2)(-) production in human blood vessels and investigated whether, and by what mechanism, Ang II might alter vascular.O(2)(-) production. METHODS AND RESULTS: Internal mammary arteries (IMAs) and saphenous veins (SVs) were collected at the time of cardiac surgery. Vessels were incubated in Krebs buffer at 37 degrees C.O(2)(-) was measured by lucigenin chemiluminescence. Basal. O(2)(-) concentrations were greater in IMAs than SVs. Inhibitors of NAD(P)H oxidase (10 micromol/L to 200 micromol/L diphenyleneiodonium) and xanthine oxidase (1 mmol/L allopurinol) caused reductions in.O(2)(-) concentrations in both IMAs and SVs. Western blotting of superoxide dismutase proteins demonstrated similar expression in IMAs and SVs. Vessels were also incubated in the presence or absence of Ang II (1 pmol/L to 1 micromol/L). Ang II increased.O(2)(-) production in IMAs at 4 hours of incubation (control, 978+/-117 pmol. min(-1). mg(-1); 1 micromol/L of Ang II, 1690+/-213 pmol. min(-1). mg(-1); n=27, P=0.0001, 95% CI 336, 925) but not in SVs. This effect was completely inhibited by coincubation of IMAs with DPI (100 micromol/L), a nonspecific Ang II antagonist ([sar(1), thre(8)]-Ang II, 1 micromol/L) and a specific Ang II type 1 (AT(1)) receptor antagonist (losartan, 1 micromol/L). Conclusions-. O(2)(-) production is greater in human IMAs than in SVs. NAD(P)H oxidase and xanthine oxidase are sources of.O(2)(-) production in these vessels. The vasoactive peptide Ang II increases.O(2)(-) production in human arteries by an AT(1) receptor-dependent mechanism.

Utility of fast cine magnetic resonance imaging and display for the detection of myocardial ischemia in patients not well suited for second harmonic stress echocardiography.

BACKGROUND: Some patients referred for pharmacological stress testing with transthoracic echocardiography (TTE) are unable to undergo testing owing to poor acoustic windows. Fast cine MRI can be used to assess left ventricular contraction, but its utility for detection of myocardial ischemia in patients poorly suited for echocardiography is unknown. METHODS AND RESULTS: One hundred fifty-three patients (86 men and 67 women aged 30 to 88 years) with poor acoustic windows that prevented adequate second harmonic TTE imaging were consecutively referred for MRI to diagnose inducible myocardial ischemia during intravenous dobutamine and atropine. Diagnostic studies were completed in an average of 53 minutes. No patients experienced myocardial infarction, ventricular fibrillation, exacerbation of congestive heart failure, or death. In patients who underwent computer-assisted quantitative coronary angiography, the sensitivity and specificity for detecting a >50% luminal diameter narrowing were 83% and 83%, respectively. In the 103 patients with a negative MRI examination, the cardiovascular occurrence-free survival rate was 97%. CONCLUSIONS: Fast cine cardiac MRI provides a mechanism to assess left ventricular contraction and diagnose inducible myocardial ischemia in patients not well suited for stress echocardiography.

Assessment of coronary arterial restenosis with phase-contrast magnetic resonance imaging measurements of coronary flow reserve.

BACKGROUND: After successful percutaneous coronary arterial revascularization, 25% to 60% of subjects have restenosis, a recurrent coronary arterial narrowing at the site of the intervention. At present, restenosis is usually detected invasively with contrast coronary angiography. This study was performed to determine if phase-contrast MRI (PC-MRI) could be used to detect restenosis noninvasively in patients with recurrent chest pain after percutaneous revascularization. METHODS AND RESULTS: Seventeen patients (15 men, 2 women, age 36 to 77 years) with recurrent chest pain >3 months after successful percutaneous intervention underwent PC-MRI measurements of coronary artery flow reserve followed by assessments of stenosis severity with computer-assisted quantitative coronary angiography. The intervention was performed in the left anterior descending coronary artery in 15 patients, one of its diagonal branches in 2 patients, and the right coronary artery in 1 patient. A PC-MRI coronary flow reserve value /=70% and >/=50%, respectively. CONCLUSIONS: Assessments of coronary flow reserve with PC-MRI can be used to identify flow-limiting stenoses (luminal diameter narrowings >70%) in patients with recurrent chest pain in the months after a successful percutaneous intervention.

Visualization and functional assessment of proximal and middle left anterior descending coronary stenoses in humans with magnetic resonance imaging.

BACKGROUND: Coronary artery bypass grafting improves survival in patients with >70% luminal diameter narrowing of the 3 major epicardial coronary arteries, particularly if there is involvement of the proximal portion of the left anterior descending (LAD) coronary artery. Measurement of coronary flow reserve can be used to identify functionally important luminal narrowing of the LAD artery. Although magnetic resonance imaging (MRI) has been used to visualize coronary arteries and to measure flow reserve noninvasively, the utility of MRI for detecting significant LAD stenoses is unknown. METHODS AND RESULTS: Thirty subjects (23 men, 7 women, age 36 to 77 years) underwent MRI visualization of the left main and LAD coronary arteries as well as measurement of flow in the proximal, middle, or distal LAD both at rest and after intravenous adenosine (140 microgram/kg per minute). Immediately thereafter, contrast coronary angiography and when feasible, intracoronary Doppler assessments of coronary flow reserve, were performed. There was a statistically significant correlation between MRI assessments of coronary flow reserve and (a) assessments of coronary arterial stenosis severity by quantitative coronary angiography and (b) invasive measurements of coronary flow reserve (P<0.0001 for both). In comparison to computer-assisted quantitative coronary angiography, the sensitivity and specificity of MRI for identifying a stenosis >70% in the distal left main or proximal/middle LAD arteries was 100% and 83%, respectively. CONCLUSIONS: Noninvasive MRI measures of coronary flow reserve correlated well with similar measures obtained with the use of intracoronary Doppler flow wires and predicted significant coronary stenoses (>70%) with a high degree of sensitivity and specificity. MRI-based measurement of coronary flow reserve may prove useful for identification of patients likely to obtain a survival benefit from coronary artery bypass grafting.

Effect of phenformin on gluconeogenesis from lactate and intracellular pH in the isolated perfused guinea pig liver.

Gluconeogenesis from lactate and hepatic cell pH (pHi) were measured in the isolated perfused livers of starved guinea pigs in the presence and absence of phenformin (phenethylbiguanide). The observed decrease in lactate consumption and glucose output in the presence of phenformin was associated with a fall in pHi. The fall in glucose output observed was considerably greater than accountable for by the decrease in lactate consumption. A possible mechanism for the pathogenesis of clinical lactic acidosis due to phenformin therapy is suggested.

Cardiac cycle-dependent changes in aortic area and distensibility are reduced in older patients with isolated diastolic heart failure and correlate with exercise intolerance.

OBJECTIVES: The goal of this study was to determine if cardiac cycle-dependent changes in proximal thoracic aortic area and distensibility are associated with exercise intolerance in elderly patients with diastolic heart failure (DHF). BACKGROUND: Aortic compliance declines substantially with age. We hypothesized that a reduction in cardiac cycle-dependent changes in thoracic aortic area and distensibility (above that which occurs with aging) could be associated with the exercise intolerance that is prominent in elderly diastolic heart failure patients. METHODS: Thirty subjects (20 healthy individuals [10 < 30 years of age and 10 > 60 years of age] and 10 individuals > the age of 60 years with DHF) underwent a magnetic resonance imaging (MRI) study of the heart and proximal thoracic aorta followed within 48 h by maximal exercise ergometry with expired gas analysis. RESULTS: The patients with DHF had higher resting brachial pulse and systolic blood pressure, left ventricular mass, aortic wall thickness and mean aortic flow velocity, and, compared with healthy older subjects, they had a significant reduction in MRI-assessed cardiac cycle-dependent change in aortic area and distensibility (p < 0.0001) that correlated with diminished peak exercise oxygen consumption (r = 0.79). After controlling for age and gender in a multivariate analysis, thoracic aortic distensibility was a significant predictor of peak exercise oxygen consumption (p < 0.04). CONCLUSIONS: Older patients with isolated DHF have reduced cardiac cycle-dependent changes in proximal thoracic aortic area and distensibility (beyond that which occurs with normal aging), and this correlates with and may contribute to their severe exercise intolerance.

The role of imidazoline receptors in blood pressure regulation.

Using the ligands [3H] clonidine and [3H] idazoxan, nonadrenergic imidazoline preferring binding sites have been identified in a range of tissues from several species including man. These sites may represent a new family of receptors. An endogenous ligand and potential clonidine displacing substance has been identified. There is strong evidence for an involvement of the nonadrenergic imidazoline [3H] clonidine labelled sites in the nucleus reticularis lateralis in blood pressure regulation, and some evidence for a role in sodium regulation in the kidney for the [3H] idazoxan labelled sites. Some drugs which were previously thought to act via alpha 2-adrenoceptors, may mediate their effects in part via these imidazoline sites.

Low-density lipoprotein and oxidised low-density lipoprotein: their role in the development of atherosclerosis.

Oxidation of low-density lipoprotein (LDL) may be implicated in the development of atherosclerotic disease. Oxidised LDL is taken up more readily by monocyte-derived macrophages than LDL. Antibodies to oxidised LDL are found in atherosclerotic lesions, Increased risk of ischaemic heart disease is associated with a preponderance of small dense LDL particles, which are more susceptible to oxidation. Proatherogenic alterations in cell biochemistry and signalling pathways occur in the presence of LDL and more markedly oxidised LDL. In vitro antioxidants inhibit changes in cell biochemistry, while in vivo, they have been shown to attenuate or reverse development of atherosclerosis.

A postsynaptic location of alpha 2 adrenoceptors in vascular smooth muscle: in vivo studies in the conscious rabbit.

The rise in blood pressure after intravenous administration of a range of alpha-adrenoceptor agonists and the effect of alpha adrenoceptor antagonists was studied in groups of conscious rabbits. Phentolamine was equally effective at blocking the pressor response to the alpha 1 adrenoceptor agonist phenylephrine and the mixed alpha 1/alpha 2 adrenoceptor agonist noradrenaline. Phenoxybenzamine which acts preferentially on alpha 1 adrenoceptors and the more specific alpha 1 adrenoceptor antagonist prazosin were more effective against phenylephrine induced rises in pressure, while yohimbine and alpha yohimbine which preferentially act on alpha 2 adrenoceptors were more effective against noradrenaline. The immediate pressor response to intravenous injections of the alpha 2 adrenoceptor agonists clonidine and guanabenz was blocked more effectively by phentolamine than prazosin when doses which gave a postsynaptic location of both alpha 1 and alpha 2 adrenoceptors both of which mediate vasoconstrictor responses in vascular smooth muscle.

Gene transfer of endothelial nitric oxide synthase but not Cu/Zn superoxide dismutase restores nitric oxide availability in the SHRSP.

OBJECTIVE: Previous studies from our group have shown a deficit in nitric oxide (NO) bioavailability and an excess production of the superoxide anion (O(2)(-)) in the stroke prone spontaneously hypertensive rat (SHRSP) compared to the normotensive Wistar Kyoto (WKY) strain. This present study has investigated whether adenoviral-mediated gene transfer of human eNOS or Cu/ZnSOD can alter the NO/O(2)(-) balance, thereby improving endothelial function. METHODS: A recombinant adenovirus, Ad/Hu/eNOS, containing the human eNOS cDNA fragment was generated by homologous recombination in 293 cells. Ad/Hu/eNOS or Ad/Cu/ZnSOD was delivered into SHRSP carotid arteries in vivo, using a titre of 2x10(9)-2x10(10) plaque forming units (pfu)/ml, and the effect on gene expression was observed 24 h later. RESULTS: Western blotting confirmed increased enzyme levels of eNOS and Cu/ZnSOD in the viral-infused vessels. Ex vivo, the pressor response to phenylephrine (PE) in the presence of L-NAME was increased in the eNOS-infused arteries relative to the contralateral controls, indicating restoration of basal NO availability to that observed in untreated control WKY rats. Infusion of the SOD virus produced a statistically insignificant increase in NO bioavailability. CONCLUSIONS: Our results support our previous findings obtained using a bovine eNOS recombinant adenovirus, that recombinant adenoviral gene transfer of human eNOS has a significant effect on NO bioavailability. In contrast, AdCu/ZnSOD gene transfer does not elicit an effect in our model. These results indicate that short-term overexpression of a recombinant eNOS, but not Cu/ZnSOD gene, in carotid arteries of the SHRSP is an effective means of locally increasing NO bioavailability to improve endothelial function.

Pharmacological characterisation of endothelium-dependent relaxation in human radial artery: comparison with internal thoracic artery.

OBJECTIVE: The aim of this study was to investigate the contribution of nitric oxide/prostanoid-independent pathways to endothelium-dependent vasorelaxation in human conduit arteries. METHODS: Rings of internal thoracic artery (ITA) and radial artery (RA) taken from patients undergoing coronary artery bypass graft surgery were suspended in 10-ml organ baths and relaxation to carbachol and bradykinin studied in the presence and absence of nitric oxide synthase (NOS) inhibitors and potassium channel blockers. RESULTS: No significant relaxation to carbachol or bradykinin was observed in ITA after NOS inhibition. In contrast, in RA less than 40% attenuation of relaxation to carbachol or bradykinin was achieved with any of the NOS inhibitors. In the presence of 20 mM K+ relaxation to carbachol and bradykinin was inhibited by 28 +/- 9% and 42 +/- 9% while in the presence of L-NAME 200 microM + 20 mM K+ relaxation was inhibited by 66 +/- 6% and 70 +/- 4% respectively in this artery. Tetraethylammonium, glibenclamide, apamin and iberiotoxin had little effect on relaxation to carbachol but charybdotoxin alone and charybdotoxin plus apamin attenuated relaxation to carbachol by 23 +/- 4% and 49 +/- 9% in RA. In the presence of L-NAME 200 microM attenuation of these relaxations were increased to 60 +/- 4% and 78 +/- 4%. CONCLUSION: In ITA relaxations to carbachol and bradykinin were mediated via nitric oxide. In contrast in RA, a conduit vessel of similar diameter, both nitric oxide-dependent and independent pathways appeared to contribute to vascular relaxation. This nitric oxide-independent relaxation involved opening of Ca2+ activated potassium channel(s). The existence of alternative pathways mediating endothelium-independent relaxation could be important under pathological conditions and may contribute to the long term survival of radial artery grafts.

Gene transfer of endothelial nitric oxide synthase improves nitric oxide-dependent endothelial function in a hypertensive rat model.

OBJECTIVE: We have shown previously that there is a relative nitric oxide deficiency at the level of vascular endothelium in the stroke-prone spontaneously hypertensive rat (SHRSP), a model of human essential hypertension, as compared to its normotensive reference strain Wistar Kyoto (WKY) rat. The aim of the current study was to investigate whether adenoviral-mediated gene transfer of an endothelial nitric oxide synthase (eNOS) cDNA (AdCMVeNOS) into carotid arteries of the SHRSP may improve endothelial function. METHODS: Enzyme activity of the recombinant eNOS protein encoded by AdCMVeNOS was tested using a Griess assay in endothelial cells in culture. Left carotid arteries of SHRSP were surgically isolated and exposed to either the AdCMVeNOS or control beta-galactosidase-containing virus, (2 x 10(9) pfu/ml) ex vivo and in vivo. The vessels were harvested 24 h after surgery and analysed by Western blotting, immunohistochemistry and by examining endothelial function ex vivo. RESULTS: Cultured endothelial cells showed almost 100% transduction with both viruses and a dose response of eNOS expression showed a five-fold increase in nitrite production for AdCMVeNOS with no change for beta-galactosidase-containing virus. Western blotting demonstrated a significant increase of eNOS expression in vessels infused with AdCMVeNOS when compared to controls. Immunohistochemistry showed highly positive staining with monoclonal antibodies against eNOS in the intact endothelial cells of the AdCMVeNOS infused vessels. The areas under the curve of the concentration responses to phenylephrine (10(-9) to 3 x 10(-6) M) in the absence and presence of NG-nitroarginine methyl ester (100 microM) showed increased basal nitric oxide bioavailability in the carotid arteries infused with AdCMVeNOS compared to the control (n = 6 for each; P = 0.0069; 95% CI, 0.864 to 3.277). CONCLUSIONS: Our results show that AdCMVeNOS is an effective tool for vascular gene transfer and that it can improve endothelial NO availability in the SHRSP, a genetic model of essential hypertension and endothelial dysfunction.

Alpha adrenoceptors and autonomic mechanisms in perinephritis hypertension in the rabbit.

Increased pressor responses to norepinephrine and other pressor agents have been reported to occur in human essential hypertension and in several animal models of experimental hypertension. These increased responses might be related to the development of hypertension or could be a secondary consequence of the elevation in blood pressure. We have examined pressor responses to alpha-adrenoceptor agonists and to angiotensin II in male New Zealand White rabbits with perinephritic hypertension. Increased pressor responses were observed for the alpha 1 adrenoceptor agonist phenylephrine and the mixed alpha 1/alpha 2-adrenoceptor agonist norepinephrine but not for the alpha 2 adrenoceptor selective agonist guanabenz or angiotensin II. The increase occurred within 7 days of surgery and in some animals was observed when mean arterial pressure was not significantly elevated. It could not readily be attributed to intimal thickening or hypertrophy of the arterial wall, altered basal levels of norepinephrine or epinephrine, changes in norepinephrine clearance, beta-adrenoceptor interactions, or decreased baroreceptor sensitivity. However, the possibility that vascular hypertrophy and decreased baroreflex sensitivity may contribute to the increase at later times cannot be excluded. In all tissues examined, specific prazosin binding was decreased in the older animals and specific clonidine binding was decreased in forebrain. However, these changes were observed in both hypertensive and sham-operated animals and were probably age-related. We believe the increased response to alpha 1-adrenoceptor agonists may be related to changes at a postreceptor site in the coupling of receptor activation to smooth muscle contraction.

Withdrawal reactions following cessation of central alpha-adrenergic receptor agonists.

Interruption of long-term treatment with alpha 2-adrenergic receptor agonists may be associated with reversal of their hemodynamic effects, clinical and biochemical evidence of increased peripheral sympathetic activity, and behavioral responses similar to those seen after narcotic or alcohol withdrawal. Reactions are most commonly observed after short-acting imidazoline drugs such as clonidine and tiamenidine. Reactions are less common after longer acting agents such as guanfacine. A new management approach to withdrawal has been evaluated, which uses a combination of alpha 1-blockade (prazosin) and cardioselective beta-blockade (atenolol) together with a benzodiazepine (chlordiazepoxide). Withdrawal reactions were not observed in eight patients in whom clonidine was withdrawn under cover of these agents. The mechanism of the withdrawal reaction may involve agonist-induced down regulation of alpha 2-adrenergic receptor affinity, number, or both. Experimental studies with the irreversible alpha-antagonist phenoxybenzamine on the turnover of alpha 2-receptors suggest that recovery of receptor number may be much slower in the brain than in the periphery.

Sex differences in the abundance of endothelial nitric oxide in a model of genetic hypertension.

A deficiency of nitric oxide may be responsible for the increased vascular resistance associated with human essential hypertension and that seen in animal models of hypertension. Premenopausal females are relatively protected from hypertension and cardiovascular complications. Levels of superoxide can influence the availability of nitric oxide. We hypothesize that there are differences in nitric oxide availability between stroke-prone spontaneously hypertensive rats (SHRSP) and Wistar-Kyoto rats (WKY) and that superoxide may be responsible for at least some of these differences. We studied vascular reactivity in endothelium-intact aortic rings from WKY and SHRSP. We measured nitric oxide synthase activity in endothelial cells removed from aortas and also measured circulating nitrite/nitrate levels. We found the response to N(G)-nitro-L-arginine methyl ester to be significantly greater in WKY compared with SHRSP (95% CI: 20 to 174; P=.015) and in females compared with males in WKY (95% CI: 143 to 333; P=.00004) and SHRSP (95% CI: 70 to 224; P=.0006). Endothelial nitric oxide synthase activity was significantly greater in SHRSP compared with WKY (95% CI: 2.3 to 17.6; P=.016). The EC50 for relaxation to carbachol was significantly greater in male rats compared with female rats (95% CI: -1.1 to -0.2; P=.003) within the SHRSP strain. The maximum relaxation to carbachol was significantly attenuated in stroke prone spontaneously hypertensive compared with Wistar-Kyoto rats (95% CI: 1.7 to 14.4; P=.015). Diethyldithiocarbamate had a significantly greater effect on the stroke prone spontaneously hypertensive rats' carbachol response than that of Wistar-Kyoto rats (95% CI: 14.3 to 47.0; P=.0008). We conclude that superoxide may be responsible for strain differences in vascular reactivity, whereas nitric oxide availability may be responsible for sex differences independently of endothelial nitric oxide synthase activity and superoxide.

Superoxide anion production is increased in a model of genetic hypertension: role of the endothelium.

The hypothesis that the decreased nitric oxide (NO) availability observed in spontaneously hypertensive stroke-prone rats (SHRSP) is due to excess superoxide (O2-) was examined. O2- generation, measured by lucigenin chemiluminescence, was studied in 12- to 16-week male and female Wistar-Kyoto rats (WKY) and SHRSP. In addition, expression of the gene encoding endothelial NO synthase, the enzyme involved in NO generation, was investigated. O2- generation was increased in male and female SHRSP (4.11+/-0.24 and 3. 84+/-0.28 nmol O2-. min-1. mg-1 respectively) compared with their WKY counterparts and was significantly higher in male than female WKY (1.22+/-0.08 in males and 0.8+/-0.08 nmol O2-. min-1. mg-1 respectively) (SHRSP versus WKY P<0.0001, 95% CI -3.39, -2.51; male versus female WKY P=0.0029, 95% CI -0.67, -0.17). Removal of the endothelium by rubbing or addition of NO synthase inhibitors attenuated O2- generation in SHRSP but not WKY. In males, removal of the endothelium reduced O2- generation from 3.86+/-0.12 to 1.35+/-0. 08 nmol. min-1. mg-1 (P<0.0001, 95% CI 2.29, 2.81), whereas addition of L-NAME caused a reduction from 4.13+/-0.17 to 1.32+/-0.16 nmol. min-1. mg-1 (P<0.0001, 95% CI 2.36, 2.83). Similar reductions were observed in females. L-arginine had no significant effect, but tetrahydrobiopterin significantly decreased O2- generation in SHRSP from 4.04+/-0.11 to 2.36+/-0.40 nmol. min-1. mg-1 (P=0.0026, 95% CI 0.89, 2.44). Endothelial NO synthase mRNA expression was significantly greater in SHRSP than in WKY and in WKY males than in WKY females. These results show that O2- generation is increased in SHRSP and that the tissue and enzymatic sources of this excess O2- appear to be the endothelium and eNOS, respectively. The increase in O2- generation could explain the decreased availability of basal NO observed in this model of genetic hypertension.