Reduction of inflammatory cytokine concentrations and improvement of endothelial functions in obese women after weight loss over one year

BACKGROUND

Visceral fat is a key regulator site for the process of inflammation, and atherosclerotic lesions are essentially an inflammatory response.

METHODS AND RESULTS

Fifty-six healthy premenopausal obese women (age range 25 to 44 years, body mass index 37.2+/-2.2, waist to hip ratio range 0.78 to 0.92) and 40 age-matched normal weight women were studied. Compared with nonobese women, obese women had increased basal concentrations of tumor necrosis factor-alpha (TNF-alpha, P<0.01), interleukin-6 (IL-6, P<0.01), P-selectin (P<0.01), intercellular adhesion molecule-1 (ICAM-1, P<0.02), and vascular adhesion molecule-1 (VCAM-1, P<0.05). Vascular responses to L-arginine (3 g IV), the natural precursor of nitric oxide, were impaired in obese women: reductions in mean blood pressure (P<0.02), platelet aggregation to adenosine diphosphate (P<0.05), and blood viscosity (P<0.05) were significantly lower as compared with those in the nonobese group. Concentrations of TNF-alpha and IL-6 were related (P<0.01) to visceral obesity, as well as to adhesin levels and responses to L-arginine. After 1 year of a multidisciplinary program of weight reduction (diet, exercise, behavioral counseling), all obese women lost at least 10% of their original weight (9.8+/-1.5 kg, range 7.5 to 13 kg). Compared with baseline, sustained weight loss was associated with reduction of cytokine (P<0.01) and adhesin (P<0.02) concentrations and with improvement of vascular responses to L-arginine.

CONCLUSION

In obese women, endothelial activation correlates with visceral body fat, possibly through inappropriate secretion of cytokines. Weight loss represents a safe method for downregulating the inflammatory state and ameliorating endothelial dysfunction in obese women.

Angiotensin-converting enzyme inhibition with quinapril improves endothelial vasomotor dysfunction in patients with coronary artery disease. The TREND (Trial on Reversing ENdothelial Dysfunction) Study

BACKGROUND

Angiotensin-converting enzyme (ACE) inhibitors may exert some of their benefits in the therapy of hypertension, congestive heart failure, and acute myocardial infarction by their improvement of endothelial dysfunction. TREND (Trial on Reversing ENdothelial Dysfunction) investigated whether quinapril might improve endothelial dysfunction in normotensive patients with coronary artery disease and no heart failure, cardiomyopathy, or major lipid abnormalities so that confounding variables that affect endothelial dysfunction could be minimized.

METHODS AND RESULTS

Using a double-blind, randomized, placebo-controlled design, we measured the effects of quinapril (40 mg daily) on coronary artery diameter responses to acetylcholine using quantitative coronary angiography. The primary response variable was the net change in the acetylcholine-provoked constriction of target segments between the baseline (prerandomization) and 6-month follow-up angiograms. The constrictive responses to acetylcholine were comparable in the placebo (n = 54) and quinapril (n = 51) groups at baseline. After 6 months, only the quinapril group showed significant net improvement in response to incremental concentrations of acetylcholine (4.5 +/- 3.0% [mean +/- SEM] versus -0.1 +/- 2.8% at 10(-6) mol/L and 12.1 +/- 3.0% versus -0.8 +/- 2.9% at 10(-4) mol/L, quinapril versus placebo, respectively; overall P = .002).

CONCLUSIONS

TREND shows that ACE inhibition with quinapril improved endothelial dysfunction in patients who were normotensive and who did not have severe hyperlipidemia or evidence of heart failure. These benefits of ACE inhibition are likely due to attenuation of the contractile effects and superoxide-generating effects of angiotensin II and to enhancement of endothelial cell release of nitric oxide secondary to diminished breakdown of bradykinin.

Continuous assessment of the cerebral vasomotor reactivity in head injury

OBJECTIVE

Cerebrovascular vasomotor reactivity reflects changes in smooth muscle tone in the arterial wall in response to changes in transmural pressure or the concentration of carbon dioxide in blood. We investigated whether slow waves in arterial blood pressure (ABP) and intracranial pressure (ICP) may be used to derive an index that reflects the reactivity of vessels to changes in ABP.

METHODS

A method for the continuous monitoring of the association between slow spontaneous waves in ICP and arterial pressure was adopted in a group of 82 patients with head injuries. ABP, ICP, and transcranial doppler blood flow velocity in the middle cerebral artery was recorded daily (20- to 120-min time periods). A Pressure-Reactivity Index (PRx) was calculated as a moving correlation coefficient between 40 consecutive samples of values for ICP and ABP averaged for a period of 5 seconds. A moving correlation coefficient (Mean Index) between spontaneous fluctuations of mean flow velocity and cerebral perfusion pressure, which was previously reported to describe cerebral blood flow autoregulation, was also calculated.

RESULTS

A positive PRx correlated with high ICP (r = 0.366; P < 0.001), low admission Glasgow Coma Scale score (r = 0.29; P < 0.01), and poor outcome at 6 months after injury (r = 0.48; P < 0.00001). During the first 2 days after injury, PRx was positive (P < 0.05), although only in patients with unfavorable outcomes. The correlation between PRx and Mean index (r = 0.63) was highly significant (P < 0.000001).

CONCLUSION

Computer analysis of slow waves in ABP and ICP is able to provide a continuous index of cerebrovascular reactivity to changes in arterial pressure, which is of prognostic significance.

Intravascular hemolysis and the pathophysiology of sickle cell disease

Hemolysis is a fundamental feature of sickle cell anemia that contributes to its pathophysiology and phenotypic variability. Decompartmentalized hemoglobin, arginase 1, asymmetric dimethylarginine, and adenine nucleotides are all products of hemolysis that promote vasomotor dysfunction, proliferative vasculopathy, and a multitude of clinical complications of pulmonary and systemic vasculopathy, including pulmonary hypertension, leg ulcers, priapism, chronic kidney disease, and large-artery ischemic stroke. Nitric oxide (NO) is inactivated by cell-free hemoglobin in a dioxygenation reaction that also oxidizes hemoglobin to methemoglobin, a non-oxygen-binding form of hemoglobin that readily loses heme. Circulating hemoglobin and heme represent erythrocytic danger-associated molecular pattern (eDAMP) molecules, which activate the innate immune system and endothelium to an inflammatory, proadhesive state that promotes sickle vaso-occlusion and acute lung injury in murine models of sickle cell disease. Intravascular hemolysis can impair NO bioavailability and cause oxidative stress, altering redox balance and amplifying physiological processes that govern blood flow, hemostasis, inflammation, and angiogenesis. These pathological responses promote regional vasoconstriction and subsequent blood vessel remodeling. Thus, intravascular hemolysis represents an intrinsic mechanism for human vascular disease that manifests clinical complications in sickle cell disease and other chronic hereditary or acquired hemolytic anemias.

Endothelial function in chronic congestive heart failure

There is evidence that the endothelium plays an important role in the control of human vascular tone by releasing endothelium-derived nitric oxide. The hypothesis that an impairment of this mechanism is involved in the increased peripheral vasoconstriction of patients with chronic congestive heart failure (CHF) was tested. Acetylcholine and N-monomethyl-L-arginine (L-NMMA), a specific inhibitor of nitric oxide synthesis from L-arginine, were infused in the brachial artery of healthy volunteer subjects (controls) and patients with severe CHF. The radial artery diameter was determined by a high-precision A-mode ultrasound device, using a 10 MHz probe. Forearm blood flow was calculated from vessel diameter and blood flow velocity measured simultaneously by Doppler. The blood flow response to acetylcholine was blunted in patients with CHF compared with that in control subjects. In contrast, the decrease in blood flow induced by L-NMMA was exaggerated in CHF, and the blood flow response to nitroglycerin was preserved. The changes in radial artery diameter induced by acetylcholine and L-NMMA were not significant in control subjects and CHF patients, but dilation of the radial artery by nitroglycerin was significantly reduced in CHF. The results demonstrate an impaired endothelium-dependent dilation of forearm resistance vessels in CHF, suggesting a reduced release of nitric oxide on stimulation. In contrast, the basal release of nitric oxide from endothelium of forearm resistance vessels is preserved or may even be enhanced, and may play an important compensatory role in chronic CHF by antagonizing neurohumoral vasoconstrictor forces in CHF.

The effect of atherosclerosis on the vasomotor response of coronary arteries to mental stress

BACKGROUND

Mental stress can cause angina in patients with coronary artery disease, but its effects on coronary vasomotion and blood flow are poorly understood. Because atherosclerosis affects the reactivity of coronary arteries to various stimuli, such as exercise, we postulated that atherosclerosis might also influence the vasomotor response of coronary arteries to mental stress.

METHODS

We studied 26 patients who performed mental arithmetic under stressful conditions during cardiac catheterization. (An additional four patients who did not perform the mental arithmetic served as controls.) Coronary segments were classified on the basis of angiographic findings as smooth, irregular, or stenosed. In 15 of the patients without focal stenoses in the left anterior descending artery, acetylcholine (10(-8) to 10(-6) mol per liter) was infused into the artery to test endothelium-dependent vasodilation. Changes in coronary blood flow were measured with an intracoronary Doppler catheter in these 15 patients.

RESULTS

The response of the coronary arteries to mental stress varied from 38 percent constriction to 29 percent dilation, whereas the change in coronary blood flow varied from a decrease of 48 percent to an increase of 42 percent. The direction and magnitude of the change in the coronary diameter were not predicted by the changes in the heart rate, blood pressure, or plasma norepinephrine level. Segments with stenoses (n = 7) were constricted by a mean (+/- SE) of 24 +/- 4 percent, and irregular segments (n = 20) by 9 +/- 3 percent, whereas smooth segments (n = 25) did not change significantly (dilation, 3 +/- 3 percent; P less than 0.0002). Coronary blood flow increased by 10 +/- 10 percent in smooth vessels, whereas the flow in irregular vessels decreased by 27 +/- 5 percent. The degree of constriction or dilation during mental stress correlated with the response to the infusions of acetylcholine (P less than 0.0003, r = 0.58).

CONCLUSIONS

Atherosclerosis disturbs the normal vasomotor response (no change or dilation) of large coronary arteries to mental stress; in patients with atherosclerosis paradoxical constriction occurs during mental stress, particularly at points of stenosis. This vasomotor response correlates with the extent of atherosclerosis in the artery and with the endothelium-dependent response to an infusion of acetylcholine. These data suggest that in atherosclerosis unopposed constriction caused by a local failure of endothelium-dependent dilation causes the coronary arteries to respond abnormally to mental stress.

Short- and long-term black tea consumption reverses endothelial dysfunction in patients with coronary artery disease

BACKGROUND

Epidemiological studies suggest that tea consumption decreases cardiovascular risk, but the mechanisms of benefit remain undefined. Endothelial dysfunction has been associated with coronary artery disease and increased oxidative stress. Some antioxidants have been shown to reverse endothelial dysfunction, and tea contains antioxidant flavonoids. Methods and Results-- To test the hypothesis that tea consumption will reverse endothelial dysfunction, we randomized 66 patients with proven coronary artery disease to consume black tea and water in a crossover design. Short-term effects were examined 2 hours after consumption of 450 mL tea or water. Long-term effects were examined after consumption of 900 mL tea or water daily for 4 weeks. Vasomotor function of the brachial artery was examined at baseline and after each intervention with vascular ultrasound. Fifty patients completed the protocol and had technically suitable ultrasound measurements. Both short- and long-term tea consumption improved endothelium- dependent flow-mediated dilation of the brachial artery, whereas consumption of water had no effect (P<0.001 by repeated-measures ANOVA). Tea consumption had no effect on endothelium-independent nitroglycerin-induced dilation. An equivalent oral dose of caffeine (200 mg) had no short-term effect on flow-mediated dilation. Plasma flavonoids increased after short- and long-term tea consumption.

CONCLUSIONS

Short- and long-term black tea consumption reverses endothelial vasomotor dysfunction in patients with coronary artery disease. This finding may partly explain the association between tea intake and decreased cardiovascular disease events.

Sympathetic nerve activity: role in regulation of blood pressure in the spontaenously hypertensive rat

Sympathetic nerve activity (SNA) and high pressure baroreceptor regulation of SNA were studied in the Okamoto strain of spontaneously hypertensive rat (SHR). Mean arterial pressure (MAP) and SNA were not significantly affected by anesthesia with low doses of pentobarbital (20-25 mg/kg). Thus, most of these studies were performed in anesthetized rats. SNA in visceral sympathetic nerves increased rapidly with age up to 24 weeks and slowly thereafter. MAP increased with SNA, following the same time course. Both SNA and MAP in SHR were significantly greater than that found in normotensive Wistar control rats of comparable ages. Abolition of ganglionic transmission with hexamethonium in both SHR and normotensive controls reduced postganglionic SNA and MAP to comparable levels. In SHR less than 16 weeks old, increased baroreceptor stimulation effectively inhibited SNA with the same sensitivity as found in Wistar control rats. However, older SHR appeared to lose their ability to completely inhibit SNA during induced hypertension, whereas in Wistar control rats as old as 52 weeks, elevation of blood pressure to 165.3 +/- 2.3 mm Hg completely suppressed SNA. These results suggest that SNA may play an important role in the development and maintenance of hypertension in SHR, and that central sympathetic centers, uninhibited by baroreceptor afferents, become active during the development of hypertension in the SHR.

Prostaglandins in severe congestive heart failure. Relation to activation of the renin--angiotensin system and hyponatremia

To determine whether prostaglandins are involved in circulatory homeostasis in congestive heart failure, we measured plasma levels of the metabolites of vasodilator prostaglandins I2 and E2 in 15 patients with severe chronic heart failure. Mean circulating levels of both metabolites were 3 to 10 times higher than those in normal subjects. Plasma levels of both metabolites correlated directly with plasma renin activity and plasma angiotensin II concentrations (r = 0.64 and 0.84, respectively). Individual serum sodium concentrations were inversely correlated with levels of prostaglandin E2 metabolites (r = -0.92, P less than 0.001) and plasma renin activity (r = -0.69, P less than 0.02). Of 23 patients with severe heart failure challenged with indomethacin (an inhibitor of prostaglandin synthesis), the 9 with hyponatremia had significant decreases in the cardiac index (1.99 +/- 0.12 to 1.72 +/- 0.13 liters per minute per square meter of body-surface area, P less than 0.001) and significant increases in the pulmonary capillary wedge pressure (17.4 +/- 2.0 to 24.0 +/- 1.9 mm Hg, P less than 0.001) and systemic vascular resistance (1882 +/- 239 to 2488 +/- 315 dyn x sec x cm-5, P less than 0.001), whereas the 14 patients with a normal serum sodium concentration had no significant hemodynamic changes. We conclude that both vasoconstrictor (renin-angiotensin) and vasodilator (prostaglandin) mechanisms are operative in patients with heart failure complicated by hyponatremia and that these mechanisms interact to modulate circulatory homeostasis.

Prognostic value of arterial pressure, endogenous vasoactive systems, and renal function in cirrhotic patients admitted to the hospital for the treatment of ascites

To identify prognostic factors in cirrhotic patients admitted to the hospital for the treatment of an episode of ascites, a survival analysis was performed in a series of 139 patients hospitalized in our Unit between 1980 and 1985. Mean follow-up was 12.8 +/- 14.2 mo (mean +/- SD). A total of 38 variables based on history, physical examination, hepatic biochemical tests, renal function tests, and endogenous vasoactive systems were analyzed for prognostic value. Eighteen of these variables had prognostic value in the univariate analysis. A multivariate analysis (Cox's regression method) disclosed that 7 of these 18 variables had independent prognostic value. Of these independent predictors of survival, mean arterial pressure and plasma norepinephrine concentration were the variables that best predicted prognosis. Two other variables that independently correlated with survival were urinary sodium excretion and glomerular filtration rate. The remaining three independent predictors of survival were nutritional status, hepatomegaly, and serum albumin concentration. Therefore, these findings indicate that, in patients with cirrhosis and ascites, parameters estimating systemic hemodynamics and renal function are better predictors of survival than those routinely used to estimate hepatic function.

Protein glycation: a firm link to endothelial cell dysfunction

The advanced glycation end products (AGEs) are a heterogeneous class of molecules, including the following main subgroups: bis(lysyl)imidazolium cross-links, hydroimidazolones, 3-deoxyglucosone derivatives, and monolysyl adducts. AGEs are increased in diabetes, renal failure, and aging. Microvascular lesions correlate with the accumulation of AGEs, as demonstrated in diabetic retinopathy or renal glomerulosclerosis. On endothelial cells, ligation of receptor for AGE (RAGE) by AGEs induces the expression of cell adhesion molecules, tissue factor, cytokines such as interleukin-6, and monocyte chemoattractant protein-1. A chief means by which AGEs via RAGE exert their effects is by generation of reactive oxygen species, at least in part via stimulation of NADPH oxidase. Diabetes-associated vascular dysfunction in vivo can be prevented by blockade of RAGE. Thus, agents that limit AGE formation, increase the catabolism of these species, or antagonize their binding to RAGE may provide new targets for vascular protection in diabetes.

Phase relationship between cerebral blood flow velocity and blood pressure. A clinical test of autoregulation

BACKGROUND AND PURPOSE

This study investigates the usefulness, as a test of dynamic autoregulation, of phase shift angle analysis between oscillations in cerebral blood flow velocity (CBFV) and in arterial blood pressure (ABP) during deep breathing.

METHODS

Fifty healthy volunteers, 20 patients with occlusive cerebrovascular diseases (OCD), and 10 patients with arteriovenous malformations (AVM) took part in the study. All subjects received transcranial Doppler monitoring of both middle cerebral arteries (MCAs). In addition, continuous blood pressure monitoring was performed with the use of noninvasive servo-controlled infrared finger plethysmography during deep breathing at a rate of 6/min. With the use of a high-pass filter model of autoregulation, autoregulation was quantified as phase shift angle between oscillations in CBFV and ABP at a frequency of 6/min. A phase shift angle of 0 degrees indicates total absence of autoregulation, while 90 degrees can be gauged as optimal autoregulation. In addition, vasomotor reactivity of both MCAs to CO2 stimulation was assessed among patients and calculated as percent increase in CBFV per millimeter of mercury of increase in CO2.

RESULTS

All normal subjects showed positive phase shift angles between CBFV and ABP (mean +/- SD, 70.5 +/- 29.8 degrees). OCD patients presented with significantly decreased phase shift angles for the MCA only on the pathological side (51.7 +/- 35.1 degrees; P < .05). Patients with AVM showed significantly reduced phase shift angles on both the affected side (26.8 +/- 13.5 degrees; P < .001) and the unaffected side (40.6 +/- 26.6 degrees; P < .01). In patients' groups, phase shift angle and vasomotor reactivity correlated significantly (r = .66; P < .001) after results from all MCAs were pooled.

CONCLUSIONS

Results confirm the high-pass filter model of cerebral autoregulation: Normal subjects showed predicted positive phase shift angles between CBFV and ABP oscillations. Patients with expected autoregulatory disturbances showed significant decreases in phase shift angles. Close correlations existed between autoregulation and CO2-induced vasomotor reactivity.

Psychosocial and socioeconomic burden of vasomotor symptoms in menopause: a comprehensive review

Many women experience vasomotor symptoms at or around the time of menopause. Hot flushes and night sweats are considered primary menopausal symptoms that may also be associated with sleep and mood disturbances, as well as decreased cognitive function. All of these symptoms may lead to social impairment and work-related difficulties that significantly decrease overall quality of life. Hot flushes have shown a great deal of variability in their frequency and severity in women. In some women, hot flushes persist for several months; in others, they may last for more than 10 years. Traditionally vasomotor symptoms were reported to begin 5 to 10 years prior to the cessation of the final menstrual cycle, corresponding with the initial decline in circulating gonadal hormones; however, night sweats in particular most often begin in perimenopause. The pathogenesis of hot flushes has not yet been fully elucidated, but the circuitry involving estrogen and neurotransmitters, norepinephrine and serotonin specifically, are hypothesized to play a major role in the altered homeostatic thermoregulatory mechanisms underlying these events.

Menopause-associated vasomotor symptoms are associated with significant direct and indirect costs. Overall costs of traditional pharmacotherapy or complementary and alternative medicine modalities, including over-the-counter treatments and dietary supplements, for managing menopause-related vasomotor symptoms are substantial and include initial and follow-up physician visits and telephone calls. Additional costs include laboratory testing, management of adverse events, loss of productivity at work, and personal and miscellaneous costs. Pharmacoeconomic analyses, including those that consider risks identified by the Women's Health Initiative, generally support the cost-effectiveness of hormonal therapy for menopause-associated vasomotor symptoms, which have been the mainstay for the management of these symptoms for more than 50 years. However, because many women now want to avoid hormone therapy, there is a need for additional targeted therapies, validated by results from controlled clinical trials that are safe, efficacious, cost-effective, and well tolerated by symptomatic menopausal women.

Atherosclerosis influences the vasomotor response of epicardial coronary arteries to exercise

We studied the vasomotion of epicardial coronary arteries during exercise and tested the hypotheses that abnormal vasoconstriction is related to the presence of atherosclerosis and may be related to endothelial dilator dysfunction. During cardiac catheterization quantitative coronary angiography was performed in 21 patients during supine bicycle exercise. 21 of 28 smooth, angiographically normal vessel segments dilated (14.0 +/- 1.8%) during exercise; four smooth segments did not change whereas only three constricted. In contrast, 15 of 16 vessel segments with irregularities constricted in response to exercise (17.0 +/- 0.1%) with only one segment dilating. All 10 stenotic segments constricted to exercise (23 +/- 4%). Six patients also received intracoronary acetylcholine before exercise to test endothelium-dependent dilator function. In five of six patients all nine vessel segments showed the same directional response to acetylcholine and exercise. Three irregular and two stenotic segments constricted with acetylcholine (51 +/- 21%) and exercise (9.0 +/- 0.6%). In contrast, four smooth segments dilated to acetylcholine (19 +/- 6%) and exercise (9 +/- 1%). Both exercise and acetylcholine generally dilated smooth but constricted irregular and stenosed coronary segments. It appears likely that atherosclerosis plays an important role in the abnormal vasomotion of diseased coronary arteries during exercise and the pattern of abnormality suggests impairment of vasodilator function.

Major racial differences in coronary constrictor response between japanese and caucasians with recent myocardial infarction

BACKGROUND

Enhanced coronary vasomotion may contribute to acute coronary occlusion during the acute phase of myocardial infarction (AMI). Japanese have a higher incidence of variant angina than Caucasian patients, but racial differences in vasomotor reactivity early after AMI are controversial.

METHODS AND RESULTS

The same team studied 15 Japanese and 19 Caucasian patients within 14 days of AMI by acetylcholine injection into non-infarct-related (NIRA) and infarct-related (IRA) coronary arteries followed by nitroglycerin. Incidence of vasodilation, vasoconstriction, spasm, and basal tone were assessed in proximal, middle, and distal segments after each drug bolus by quantitative angiography. Japanese patients had much lower cholesterol levels than Caucasians (183+/-59 versus 247+/-53 mg/dL, P<0.006) but showed a lower incidence of vasodilation (2% versus 9% of coronary segments) and a greater incidence of spasm after acetylcholine (47% versus 15% of arteries, P<0.00001). Incidence of spasm was higher in IRAs than in NIRAs in both populations (67% versus 39% and 23% versus 11%, respectively). Multivessel spasm was more common (64% versus 17%, P<0.02) and vasoconstriction of nonspastic segments was greater in Japanese patients (-23.4+/-14.9% versus -20.1+/-15.7%, P<0.02) in the presence of similar average basal coronary tone with respect to post-nitroglycerin dilation and of nonsignificant differences of coronary atherosclerotic score.

CONCLUSIONS

Soon after AMI, Japanese patients exhibited a 3-fold-greater incidence of spasm and greater vasoconstriction of nonspastic segments after acetylcholine than Caucasians. The causes of such differences warrant further investigation because they may have relevant pathophysiological and therapeutic implications.

Increased reactive oxygen species in rostral ventrolateral medulla contribute to neural mechanisms of hypertension in stroke-prone spontaneously hypertensive rats

BACKGROUND

Oxidative stress increases in hypertension. The aim of this study was to determine whether reactive oxygen species (ROS) are increased in the rostral ventrolateral medulla (RVLM) in the brainstem, where the vasomotor center is located, in stroke-prone spontaneously hypertensive rats (SHRSP), and, if so, to determine whether the increased ROS contribute to neural mechanisms of hypertension in SHRSP.

METHODS AND RESULTS

We measured ROS levels in the RVLM of SHRSP and compared them with those in Wistar-Kyoto rats (WKY). Thiobarbituric acid-reactive substances were increased in SHRSP compared with WKY. ROS were measured by electron spin resonance (ESR) spectroscopy. The ESR signal decay rate in the RVLM of SHRSP was significantly increased compared with that in WKY, and this increase was abolished by dimethylthiourea (a hydroxyl radical scavenger). The increased ESR signal decay rate was reduced to the same extent in the presence of desferrioxamine, catalase, and Tiron, indicating that hydroxyl radicals are derived from superoxide anions and hydrogen peroxide. In addition, total superoxide dismutase (SOD) activity in the RVLM was decreased in SHRSP compared with WKY. Furthermore, bilateral microinjection of tempol into the RVLM decreased blood pressure in SHRSP but not in WKY, and MnSOD overexpression in the RVLM of SHRSP decreased blood pressure and inhibited sympathetic nerve activity.

CONCLUSIONS

These results suggest that superoxide anions in the RVLM, which generate hydroxyl radicals, are increased in SHRSP and contribute to the neural mechanisms of hypertension in SHRSP.

Racial heterogeneity in coronary artery vasomotor reactivity: differences between Japanese and Caucasian patients

Japanese investigators have provided a substantial contribution in the understanding of coronary vasomotor reactivity. On occasions, their findings have been at variance with those undertaken on caucasian patients, raising speculation that vasomotor differences between races may exist. In a comparative review of the published literature, we evaluated the vasoreactive differences among Japanese and caucasian patients with variant angina or myocardial infarction. In variant angina, Japanese patients appear to have diffusely hyperreactive coronary arteries compared with caucasian people, manifested by their segmental rather than focal spasm, hyperreactive nonspastic vessels and multivessel spasm. These differences may reflect the increased basal tone among Japanese variant angina patients and may relate to controversial differences in endothelial nitric oxide production or autonomic nervous system activity. Provocative vasomotor studies of Japanese patients with a recent myocardial infarction report a higher incidence of inducible spasm than caucasian studies, an observation recently supported by a controlled study. Furthermore, the hyperreactivity was diffuse, occurring in both non-infarct- and infarct-related vessels. These observations support the existence of racial coronary vasomotor reactivity differences but require confirmation in further prospectively conducted studies.

Sympathetic outflow to muscles during vasovagal syncope

Sympathetic vasoconstrictor impulses were recorded with microelectrodes in peroneal muscle nerve fascicles during vasovagal syncope in two subjects. After a preceding period of increased nerve activity, onset of syncope was associated with bradycardia and sudden cessation of sympathetic outflow. The findings provide direct evidence that neurally mediated muscular vasodilatation occurring during syncope is due to inhibition of vasoconstrictor impulses.

Transjugular intrahepatic portosystemic shunt in hepatorenal syndrome: effects on renal function and vasoactive systems

Little information exists on the effects of transjugular intrahepatic portosystemic shunts (TIPS) in the management of cirrhotic patients with hepatorenal syndrome (HRS). The current study was aimed to prospectively evaluate the effects of TIPS on renal function and vasoactive systems in patients with type I HRS. Glomerular filtration rate (GFR) (inulin clearance), renal plasma flow (RPF) (para-aminohippurate clearance), plasma renin activity (PRA), aldosterone (ALDO), norepinephrine (NE), and endothelin (ET) were determined in baseline conditions and at different time intervals after TIPS in 7 patients with type I HRS. TIPS induced a marked reduction of portal pressure gradient (PPG) (20 +/- 1 to 10 +/- 1 mm Hg; P < .05). Renal function improved in 6 of the 7 patients. Serum creatinine and blood urea nitrogen (BUN) decreased from 5 +/- 0.8 and 109 +/- 7 to 1.8 +/- 0.4 mg/dL and 56 +/- 11 mg/dL, respectively (P < .05 for both), and GFR and RPF increased from 9 +/- 4 and 103 +/- 33 to 27 +/- 7 mL/min and 233 +/- 40 mL/min, respectively (P < .05 for both), 30 days after TIPS. These beneficial effects on renal function were associated with a significant (P < .05) reduction of PRA (18 +/- 5 to 3 +/- 1 ng/mL x h), ALDO (279 +/- 58 to 99 +/- 56 ng/dL), and NE (1,257 +/- 187 to 612 +/- 197 pg/mL). ET did not change significantly (28 +/- 8 to 27 +/- 11 pg/mL). Mean survival was 4.7 +/- 2 months (0.3-17 months). Three patients remained alive more than 3 months after TIPS insertion. In conclusion, TIPS improves renal function and reduces the activity of the renin-angiotensin and sympathetic nervous systems in cirrhotic patients with type I HRS. Nevertheless, the efficacy of TIPS in the management of these patients should be confirmed in controlled investigations.