4-Aminopyridine, A Blocker of Voltage-Dependent K+ Channels, Restores Blood Pressure and Improves Survival in the Wistar Rat Model of Anaphylactic Shock.

OBJECTIVES: Anaphylactic shock is associated with severe hypotension. Potassium channel blockers, such as 4-aminopyridine, induce vasoconstriction. The objective of this study was to test the ability of 4-aminopyridine to restore blood pressure and increase survival in anaphylactic shock. DESIGN: Experimental study. SETTING: Physiology laboratory. SUBJECTS: Adult male Wistar rats. INTERVENTIONS: Rats were sensitized with ovalbumin (1 mg SC), and anaphylactic shock was induced by IV injection of ovalbumin (1 mg). Experimental groups included non-allergic rats (NA) (n = 6); allergic rats (Controls) (n = 6); allergic rats treated with 4-aminopyridine (4-aminopyridine) (1 mg/kg) (n = 6); and allergic rats treated with epinephrine (EPI) (10 µg/kg) (n = 6). Treatments were administered 1 minute after induction of anaphylactic shock. MEASUREMENTS AND MAIN RESULTS: Mean arterial blood pressure, heart rate, and survival were measured for 60 minutes. Plasma levels of histamine, leukotriene B4, prostaglandin E2, prostaglandin F2, pH, and HCO3 were measured. Mean arterial blood pressure was normal in the NA group; severe hypotension and high mortality were observed in controls; normalization of mean arterial blood pressure, heart rate, and increased survival were observed in 4-aminopyridine and EPI groups. All allergic 4-aminopyridine-treated rats survived after the induction of anaphylactic shock. Histamine level was higher in controls and the 4-aminopyridine group but reduced in the EPI group. Prostaglandin E2 increased in controls and EPI group and decreased in 4-aminopyridine group; prostaglandin F2 increased in controls but decreased in 4-aminopyridine and EPI groups. Leukotriene B4 decreased in 4-aminopyridine and EPI groups. Metabolic acidosis was prevented in the 4-aminopyridine group. CONCLUSIONS: Our data suggest that voltage-dependent K+ channel inhibition with 4-aminopyridine treatment restores blood pressure and increases survival in the Wistar rat model of anaphylactic shock. 4-aminopyridine or related voltage-dependent K channel blockers could be a useful additional therapeutic approach to treatment of refractory anaphylactic shock.

Short-term systemic effects of nose-only cigarette smoke exposure in mice: role of oxidative stress.

BACKGROUND/AIMS: Long-term cigarette smoking (CS) is a major risk factor for respiratory and cardiovascular diseases, and is also known to adversely affect other organs. However, data on the systemic effects of short-term CS exposure (STCSE) are scarce. Presently, using a nose-only exposure system, we evaluated the systemic effects of STCSE in mice. METHODS: We assessed the effects of CS generated by 9 consecutive cigarettes per day for 4 days in a nose-only exposure system on cardiovascular, hepatic and renal endpoints evaluated on day 5 in mice. Control mice were exposed to air only. RESULTS: CS significantly increased systolic blood pressure and decreased total nitric oxide plasma concentration. Circulating platelets and erythrocyte numbers were also increased. However, STCSE did not significantly increase thrombosis in pial arterioles and venules. STCSE significantly raised plasma alanine aminotransferase and gamma glutamyl transpeptidase activities, but did not affect urea or creatinine concentrations. Interestingly, while STCSE enhanced the production of reactive oxygen species in heart and kidney and lipid peroxidation in heart, liver and kidneys, it also enhanced the antioxidant activity of superoxide dismutase, probably indicating that STCSE causes adaptive reactions to counterbalance the potentially damaging action of oxygen radicals induced by STCSE. CONCLUSION: These results suggest that STCSE causes blood pressure increase, hepatotoxicity and oxidative stress in the heart, liver and the kidneys. These data provide information on the initial steps leading to the systemic effects of STCSE, a stage at which the diseases may likely be reversed.

Effects of dehydration and blockade of angiotensin II AT1 receptor on stress hormones and anti-oxidants in the one-humped camel.

BACKGROUND: The objective of this study was to provide for the first time data on plasma catecholamines, cortisol, glutathione and malondialdehyde after long term dehydration (20 days) in the presence and absence of angiotensin II (Ang II) AT1 receptor blocker (losartan) versus levels in time-matched, non-dehydrated control camels and to record the responses of glutathione and malondialdehyde activity in liver and kidney homogenates in control, dehydrated-losartan treated and dehydrated camels. Eighteen male camels were studied, six hydrated (control group), six dehydrated and treated with losartan (treated group) and six dehydrated not treated (dehydrated). RESULTS: Plasma levels of norepinephrine and dopamine were significantly increased (P < 0.01) in both treated and dehydrated groups compared to time matched control, whereas Plasma epinephrine level showed significant decrease (P < 0.05) in both treated and dehydrated groups compared to control. Plasma cortisol also showed significant increase (P < 0.01) in both treated and dehydrated groups compared to control. Glutathione levels in plasma, liver and kidney homogenates for both treated and dehydrated groups reveled significant increase (P < 0.05) Likewise, malondialdehyde levels in plasma, liver and kidney homogenates were substantially and significantly increased in both treated and dehydrated groups. CONCLUSION: In conclusion, the results of this study demonstrated that dehydration substantially increased the circulating levels of norepinephrine, dopamine and cortisol but decreased plasma epinephrine. Similarly, losartan showed similar effects to that of dehydration. In addition, this investigation showed dehydration alone or in combination with losartan induced significant increments in glutathione and malondialdehyde activities in plasma, liver and kidney homogenates, presumably in order to counteract the potentially damaging effects of free radicals. Blockade of angiotensin II AT1 receptors did not alter significantly the response of dehydration in any of these indices.

Combined Treatment with KV Channel Inhibitor 4-Aminopyridine and either γ-Cystathionine Lyase Inhibitor ß-Cyanoalanine or Epinephrine Restores Blood Pressure, and Improves Survival in the Wistar Rat Model of Anaphylactic Shock.

The mechanism of anaphylactic shock (AS) remains incompletely understood. The potassium channel blocker 4-aminopyridine (4-AP), the inhibitors of cystathionine γ-lyase (ICSE), dl-propargylglycine (DPG) or ß-cyanoalanine (BCA), and the nitric oxide (NO) synthase produce vasoconstriction and could be an alternative for the treatment of AS. The aim of this study was to demonstrate the ability of L-NAME, ICSE alone or in combination with 4-AP to restore blood pressure (BP) and improve survival in ovalbumin (OVA) rats AS. Experimental groups included non-sensitized Wistar rats (n = 6); AS (n = 6); AS (n = 10 per group) treated i.v. with 4-AP (AS+4-AP), epinephrine (AS+EPI), AS+DPG, AS+BCA, or with L-NAME (AS+L-NAME); or AS treated with drug combinations 4-AP+DPG, 4-AP+BCA, 4-AP+L-NAME, or 4-AP+EPI. AS was induced by i.v. OVA (1 mg). Treatments were administered i.v. one minute after AS induction. Mean arterial BP (MAP), heart rate (HR), and survival were monitored for 60 min. Plasma levels of histamine, prostaglandin E2 (PGE2) and F2 (PGF2α), leukotriene B4 and C4, angiotensin II, vasopressin, oxidative stress markers, pH, HCO3, PaO2, PaCO2, and K+ were measured. OVA induced severe hypotension and all AS rats died. Moreover, 4-AP, 4-AP+EPI, or 4-AP+BCA normalized both MAP and HR and increased survival. All sensitized rats treated with 4-AP alone or with 4-AP+BCA survived. The time-integrated MAP "area under the curve" was significantly higher after combined 4-AP treatment with ICSE. Metabolic acidosis was not rescued and NO, ICSE, and Kv inhibitors differentially alter oxidative stress and plasma levels of anaphylactic mediators. The AS-induced reduction of serum angiotensin II levels was prevented by 4-AP treatment alone or in combination with other drugs. Further, 4-AP treatment combined with EPI or with BCA also increased serum PGF2α, whereas only the 4-AP+EPI combination increased serum LTB4. Serum vasopressin and angiotensin II levels were increased by 4-AP treatment alone or in combination with other drugs. Moreover, 4-AP alone and in combination with inhibition of cystathionine γ-lyase or EPI normalizes BP, increases serum vasoconstrictor levels, and improves survival in the Wistar rat model of AS. These findings suggest possible investigative treatment pathways for research into epinephrine-refractory anaphylactic shock in patients.

Cellular and Immunohistochemical Changes in Anaphylactic Shock Induced in the Ovalbumin-Sensitized Wistar Rat Model.

Anaphylactic shock (AS) is a life-threatening, multisystem disorder arising from sudden release of mast cell- and basophil-derived mediators into the circulation. In this study, we have used a Wistar rat model to investigate AS-associated histopathologic changes in various organs. Rats were sensitized with ovalbumin (1 mg s.c), and AS was induced by intravenous injection of ovalbumin (1 mg). Experimental groups included nonallergic rats (n = 6) and allergic rats (n = 6). Heart rate and blood pressure were monitored during one hour. Organs were harvested at the end of the experiment and prepared for histologic and immunohistochemical studies. Lung, small bowel mucosa and spleen were found to undergo heavy infiltration by mast cells and eosinophils, with less prominent mast cell infiltration of cardiac tissue. The mast cells in lung, small bowel and spleen exhibited increased expression of tryptase, c-kit and induced nitric oxide synthase (iNOS). Increased expression of endothelial nitric oxide synthase (eNOS) by vascular endothelial cells was noted principally in lung, heart and small bowel wall. The Wistar rat model of AS exhibited accumulation of mast cells and eosinophils in the lung, small bowel, and spleen to a greater extent than in the heart. We conclude that lung and gut are principal inflammatory targets in AS, and likely contribute to the severe hypotension of AS. Targeting nitric oxide (NO) production may help reduce AS mortality.

Bronchoalveolar matrix metalloproteinase 9 relates to restrictive lung function impairment in systemic sclerosis.

Systemic sclerosis (SSc) is frequently associated with interstitial lung disease (ILD) often leading to lung fibrosis. In this study we investigated whether matrix metalloproteinase 9 (MMP-9) and its natural inhibitor; the tissue inhibitor of matrix metalloproteinase 1 (TIMP-1), would be associated with remodelling in ILD in SSc. Levels of total MMP-9, pro-MMP-9 and TIMP-1 were measured in bronchoalveolar lavage (BAL) fluid from nine SSc patients with ILD, seven SSc patients without ILD and 16 age- and sex-matched healthy controls. Total MMP-9 and pro-MMP-9 levels were significantly elevated in SSc patients with ILD, compared to levels in SSc patients without ILD and healthy controls. In SSc patients with ILD calculated active MMP-9 levels were significantly higher than in SSc patients without ILD and tended to be higher than in healthy controls. TIMP-1 levels were elevated in both patient groups compared to healthy controls. Total-, pro- and active MMP-9 levels as well as pro-MMP-TIMP-1 and active MMP-9/TIMP-1 ratios were inversely associated with total lung capacity. The present study suggests that MMP-9 plays a pathophysiological role in the remodelling in ILD and lung fibrosis associated with SSc, and may represent a new therapeutic target in this condition.

Hypothesis: Correction of low vitamin D status among Arab women will prevent heart failure and improve cardiac function in established heart failure.

Vitamin D deficiency is common in Arab countries particularly among women. This is the result of a low dietary intake of the vitamin, limited exposure to sunlight (a paradox in view of the high sunshine figures), skin colour, obesity and high parity. Apart from its adverse effects on bone in women and their offspring, vitamin D deficiency has the potential to cause or exacerbate heart failure through a number of mechanisms including activation of the renin-angiotensin system and increased arterial pressure. Accordingly, we propose that ensuring adequate vitamin D levels in Arab women will have a much greater impact on health than just the prevention of bone disease. In particular, we suggest that prevention and correction of vitamin D deficiency will reduce the incidence of heart failure and, for Arab women with established heart failure and vitamin D deficiency, improve cardiac function.

Effects of brain natriuretic peptide on contraction and intracellular Ca2+ in ventricular myocytes from the streptozotocin-induced diabetic rat.

The streptozotocin (STZ)-treated rat is a widely studied experimental model of diabetes mellitus (DM). Its pathophysiology includes hypoinsulinemia, hyperglycemia, cardiac hypertrophy, and a cardiomyopathy that is characterized by the presence of diastolic and/or systolic contractile dysfunction. As part of their endocrine function cardiomyocytes in the heart produce and secrete a family of related peptide hormones called the natriuretic peptides that include A-type natriuretic peptide (ANP) and B-type natriuretic peptide (BNP). ANP and BNP levels are variously augmented in patients with hypertension, cardiac overload, in the ventricles of failing or hypertrophied heart, in cardiac heart failure, in acute myocardial infarction (MI), and in some circumstances in DM. In this article, the effects of BNP on ventricular myocyte contraction and Ca2+ transport in STZ-induced diabetic rats have been investigated. BNP concentration was significantly increased in blood plasma and in atrial muscle in STZ-induced diabetic rats compared to age-matched controls. BNP was 11.9 +/- 0.9 ng/mL in plasma from diabetic rats compared to 6.7 +/- 1.6 ng/mL in controls and 15.8 +/- 2.0 ng/mg protein in diabetic atrial muscle compared to 8.5 +/- 1.0 ng/mg protein in controls. The heart weight to body weight ratio, an indicator of hypertrophy, was significantly increased in diabetic rat heart (4.3 +/- 0.1 mg/g) compared to controls (3.7 +/- 0.04 mg/g). The amplitude of shortening was not significantly altered in diabetic myocytes (10.3 +/- 0.4%) compared to controls (10.9 +/- 0.4%). BNP reduced the amplitude of shortening to a greater extent in diabetic myocytes (8.1 +/- 0.6%) compared to controls (10.1 +/- 0.4%). The time to peak (TPK) shortening was significantly prolonged in diabetic myocytes (254 +/- 8 ms) compared to controls (212 +/- 5 ms) and was not additionally altered by BNP. The time to half relaxation of shortening was also significantly prolonged in diabetic myocytes (131 +/- 8 ms) compared to controls (111 +/- 5 ms). BNP (10(-8) to 10(-6) M) normalized the time to half relaxation of shortening in diabetic myocytes to that of controls. Time to peak (TPK) shortening of Ca2+ was not different between diabetic and control rats. However, BNP (10(-7) M) increases TPK of Ca2+ significantly. The amplitude of the Ca2+ transient was significantly increased in diabetic myocytes (0.42 +/- 0.02 Ratio units [RU]) compared to controls (0.36 +/- 0.02 RU) and was not additionally altered by BNP. BNP may have a protective role in STZ-induced diabetic rat heart.

Right ventricular myocardial isovolumic relaxation time and pulmonary pressure.

AIMS: Non-invasive assessment of pulmonary artery systolic pressure (PASP) has several limitations. As previously described by Burstin, the right ventricular (RV) isovolumic relaxation time (IVRt) is sensitive to changes in PASP. We therefore compared RV myocardial IVRt, derived by Doppler tissue imaging (DTI), with simultaneously measured invasive PASP. METHODS AND RESULTS: Twenty-six consecutive patients (18 males, mean age 52 +/- 12 years, range 23-75) underwent a simultaneous Doppler echocardiography, including DTI, and cardiac catheterization examination for measurement of PASP and right atrial mean pressures. IVRt was measured using the myocardial velocities by pulsed DTI at both basal and mid cavity segments of the RV free wall. As diastolic time intervals are influenced by heart rate IVRt was corrected for heart rate (IVRt/RR%). A significant correlation was found between PASP and regional IVRt/RR% at both the basal (r = 0.42, P<0.05) and mid cavity segment (r = 0.71, P<0.001). Furthermore, when only patients with normal right atrial pressures (<7 mmHg) were taken into account, the correlation coefficient improved at both basal and mid cavity segments (r = 0.74, P<0.05 and r = 0.83, P<0.01). CONCLUSION: Pulsed Doppler-derived IVRt correlates well with PASP. The use of pulsed DTI for measurement of IVRt is simple, reproducible and easy to obtain. We propose this method as an additional non-invasive tool in the assessment of PASP.

Oxidative stress, inflammation, and DNA damage in multiple organs of mice acutely exposed to amorphous silica nanoparticles.

The use of amorphous silica (SiO2) in biopharmaceutical and industrial fields can lead to human exposure by injection, skin penetration, ingestion, or inhalation. However, the in vivo acute toxicity of amorphous SiO2 nanoparticles (SiNPs) on multiple organs and the mechanisms underlying these effects are not well understood. Presently, we investigated the acute (24 hours) effects of intraperitoneally administered 50 nm SiNPs (0.25 mg/kg) on systemic toxicity, oxidative stress, inflammation, and DNA damage in the lung, heart, liver, kidney, and brain of mice. Lipid peroxidation was significantly increased by SiNPs in the lung, liver, kidney, and brain, but was not changed in the heart. Similarly, superoxide dismutase and catalase activities were significantly affected by SiNPs in all organs studied. While the concentration of tumor necrosis factor α was insignificantly increased in the liver and brain, its increase was statistically significant in the lung, heart, and kidney. SiNPs induced a significant elevation in pulmonary and renal interleukin 6 and interleukin-1 beta in the lung, liver, and brain. Moreover, SiNPs caused a significant increase in DNA damage, assessed by comet assay, in all the organs studied. SiNPs caused leukocytosis and increased the plasma activities of lactate dehydrogenase, creatine kinase, alanine aminotranferase, and aspartate aminotransferase. These results indicate that acute systemic exposure to SiNPs causes oxidative stress, inflammation, and DNA damage in several major organs, and highlight the need for thorough evaluation of SiNPs before they can be safely used in human beings.

Plasma BNP in patients on maintenance haemodialysis: a guide to management?

The number of patients requiring long-term haemodialysis is increasing throughout the world. Cardiovascular disease is much more common in these patients than in the general population and accounts for the majority of deaths. New approaches to management are clearly needed to reduce this excessive cardiovascular burden. We propose that circulating levels of the cardiac natriuretic peptides, B-type natriuretic peptide (BNP) in particular, might provide a useful, objective guide to the management of their hydration status and pharmacotherapy. An overview of the literature shows that plasma levels of the cardiac natriuretic peptides are increased in this patient population and reflect cardiac preload and afterload along with cardiac pathology, thereby providing an index of cardiovascular (especially cardiac) stress and distress. Circulating levels of the cardiac peptides change in parallel with cardiac load, especially across haemodialysis. Furthermore, there is robust evidence that natriuretic peptide levels are predictive of cardiovascular outcome in these patients. Accordingly, we hypothesize that management of their haemodialysis, and pharmacotherapy designed specifically to lower plasma BNP levels to, or close to, the normal range, will reduce the excessive burden on the cardiovascular system and thereby ultimately lower the incidence of cardiovascular disease. We outline, in broad terms, how a trial to test this hypothesis might be designed.

Disturbed right ventricular diastolic function in patients with systemic sclerosis: a Doppler tissue imaging study.

BACKGROUND: Cardiopulmonary involvement in patients with systemic sclerosis (SSc) carries a poor prognosis, mainly due to pulmonary hypertension and right-heart failure. To date, right ventricular (RV) involvement has not been studied in detail. We therefore assessed RV function in patients with SSc and related the findings to the clinical features of the disease. METHOD: Twenty-six consecutive patients (21 women) with SSc (mean age, 56 +/- 15 years [+/- SD]) and 25 healthy, age-matched control subjects (21 women) were studied. Doppler echocardiography including Doppler tissue imaging was used to evaluate cardiac function. Pulmonary function was also studied. RESULTS: Compared with control subjects, RV free wall thickness (5.8 +/- 1.7 mm vs 3.7 +/- 1.1 mm, p < 0.001) and right atrial (RA) systolic area (15.9 +/- 3.7 cm2 vs 13.0 +/- 2.3 cm2, p < 0.01) were increased in patients with SSc, while the global early diastolic/atrial component velocity ratio was reduced (1.2 +/- 0.4 vs 1.7 +/- 0.6, p < 0.01). The global isovolumic relaxation time (IVRT) [64 +/- 23 ms vs 39 +/- 13 ms, p < 0.001] and regional IVRT (83 +/- 40 ms vs 46 +/- 24 ms, p < 0.001) were prolonged in patients vs control subjects, whereas the RV global filling time was reduced (454 +/- 122 ms vs 548 +/- 104 ms, p < 0.01). RV systolic function and pulmonary pressures at rest were similar in the two groups, but the pulmonary artery acceleration time was reduced (119 +/- 34 ms vs 141 +/- 29 ms, p < 0.05) in patients compared to control subjects. Left ventricular function did not differ between the two groups. CONCLUSION: Patients with SSc exhibit altered RV diastolic function together with an increase in RV wall thickness and RA area. These findings appear to be early markers of RV disturbance, probably in response to intermittent pulmonary arterial hypertension.

Parasympathetic dysfunction in hypertrophic cardiomyopathy assessed by heart rate variability: comparison between short-term and 24-h measurements.

In this study, we evaluate cardiac autonomic function in hypertrophic cardiomyopathy (HCM) by assessing heart rate variability (HRV), comparing a short-term laboratory method with an ambulatory (24-h) method, in patients with and without beta-blockade. Reduced HRV is a risk factor for adverse events in some cardiac diseases, but is not a proven risk indicator in HCM. Analysis of HRV has been based on either short- or long-term electrocardiographic recordings and previous studies in HCM have shown conflicting results. There is no consensus on which method to prefer, and we evaluate, for the first time, both short- and long-term analyses in patients with HCM. Long- and short-term HRV analyses were performed in 43 patients with HCM. They were divided in two groups, 22 patients on beta-blockade and 21 non-treated patients. As controls, 121 healthy subjects were used. Young patients without beta-blockade showed a reduction in HRV parameters reflecting parasympathetic function, both in the short- and long-term registrations, which was attenuated by beta-blockade. Parasympathetic autonomic regulation was found to be impaired in young patients with HCM. This may be of clinical relevance as abnormal autonomic function might be a substrate for malignant dysrhythmias. The impairment was attenuated by beta-blockade, which might indicate a clinically useful effect. We also show that short- and long-term methods yield similar results, suggesting that a short-term registration might be sufficient to assess HRV in patients with HCM.

Establishment of a course for Focused Assessment Sonography for Trauma.

OBJECTIVE: Focused Assessment Sonography for Trauma (FAST) is not widely practiced by Trauma Surgeons in the Middle East despite its international acceptance. A FAST course was established by the Trauma Group at the Faculty of Medicine and Health Sciences at United Arab Emirates (UAE) University aiming to introduce doctors who have limited experience of ultrasound to the basics of FAST. This article summarizes the content of the course; the evaluation of the participants and their recommendations. METHODS: An 8 hour FAST course was offered to 18 participants in May 2004 in the Faculty of Medicine and Health Sciences, UAE University, Al-Ain, UAE. Lectures with syllabus material were used to cover the following topics: basic ultrasound physics, knobology and sonographic orientation, the FAST scan, chest and cardiac trauma sonographic evaluation, training and credentialing issues. Each participant received 3 hours of hands-on ultrasound instruction. On completion of the course participants responded anonymously to an evaluation questionnaire. RESULTS: All participants responded to the questionnaire (100% response rate). Delegates found the course well organized, relevant, met their needs and encourages them to use FAST in their own practice. The course objectives were met. Participants suggested that including actual patients and the use of animal models improve the practical sessions. CONCLUSION: Organizing a FAST course is an important step towards recognizing and implementing it in practice. Nevertheless, there is a need for appropriate quality assurance and credentialing guidelines before commencing.

Potentiation of cisplatin-induced nephrotoxicity by repeated exposure to diesel exhaust particles: An experimental study in rats.

Several epidemiological and clinical studies have shown that exposure to particulate air pollution is associated with increases in morbidity and mortality, and this is more evident in patients with renal diseases. However, the basis of the possible exacerbating effect of particulate air pollution on animal model of renal injury has received scant attention. Here, we assessed the effect of repeated exposure to diesel exhaust particles (DEP) on cisplatin (CP)-induced nephrotoxicity in rats. DEP (0.5 m/kg) was intratracheally (i.t.) instilled every second day for eight days (a total of five exposures). CP, 6 mg/kg was given 1 h before the third exposure to DEP. Two days following the last exposure to either DEP or saline (control), various renal endpoints were measured. Water intake, urine volume, and relative kidney weight were significantly increased in CP + DEP versus DEP and CP + saline versus saline. Plasma creatinine increased and creatinine clearance decreased in CP + DEP versus DEP and CP + saline versus saline. Interestingly, blood urea nitrogen, albumin concentrations, and gamma-glutamyl transpeptidase (GGT) activity in urine were significantly increased in DEP + CP compared with either DEP or saline + CP. The combination of DEP and CP enhanced kidney injury molecule-1, neutrophil gelatinase-associated lipocalin, 8-isoprostane and total nitric oxide in the kidney compared with either saline + CP or DEP. Similarly, systolic blood pressure was increased in CP + DEP versus CP + saline or DEP. The renal tubular necrosis observed in kidneys of CP-treated rats was aggravated by the combination of CP + DEP. We conclude that repeated exposure to DEP potentiated CP-induced nephrotoxicity. Our data provide experimental evidence that patients with kidney injury could be at higher risk than the general population.

Glyburide, a K(+)(ATP)channel blocker, improves hypotension and survival in anaphylactic shock induced in Wistar rats sensitized to ovalbumin.

Allergens can induce anaphylactic shock and death due to serve hypotension. Potassium channel blockers (K(+)(ATP)) such as glyburide (GLY) induce vasoconstriction. The effect of (K(+)(ATP)) channel blockers on anaphylactic shock is poorly understood. Objective of the study was to test the hypothesis that GLY reduces hypotension induced in anaphylactic shock and increases survival. Rats were grouped into: G1-N=Naïve; G2-SC=Sensitized-Control; G3-SG=Sensitized-GLY (glyburide 40 mg/kg); G4-SE=Sensitized-EPI (epinephrine 10 mg/kg). G2 to G4 groups were sensitized with ovalbumin (OVA) and shock was induced by i.v. injection of OVA. Treatments were administered intravenously 5 min later. Mean arterial pressure (MAP), heart rate (HR), and mean survival time (MST) were measured for 60 min following OVA injection and treatments administration. At the end of the experiment, blood withdrawal was performed to measure plasma levels of histamine, leukotriene B(4) (LTB(4)), prostaglandin E(2) (PGE(2)) and prostaglandin F(2) (PGF(2)). Additionally blood gas (paO2, paCO2, SaO2) and electrolytes (Na(+), K(+) and Ca (++)) were measured. MAP was normal in G1-N; severe hypotension, negative inotropic and short MST were observed in G2-SC; normalization of MAP, with lesser negative inotropism and increased MST were observed in G3-SG; full recovery was observed in G4-SE. Histamine level was significantly higher in G2-SC; reduced in G3-SG and G4-SE. PGE(2) increased in G3-SG; PGF(2) increased in G2-SC and G3-SG. Na(+) and Ca (++) concentration decreased in sensitized rats but reversed in treated groups, without change in K(+) concentration. In conclusion, our data suggest that administration of GLY reduced hypotension and increases survival time in rat anaphylactic shock.

ANP and BNP responses to dehydration in the one-humped camel and effects of blocking the renin-angiotensin system.

The objectives of this study were to investigate and compare the responses of atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) in the circulation of hydrated, dehydrated, and dehydrated losartan - treated camels; and to document the cardiac storage form of B-type natriuretic peptide in the camel heart. Eighteen male camels were used in the study: control or hydrated camels (n = 6), dehydrated camels (n = 6) and dehydrated losartan-treated camels (n = 6) which were dehydrated and received the angiotensin II (Ang II) AT-1 receptor blocker, losartan, at a dose of 5 mg/kg body weight intravenously for 20 days. Control animals were supplied with feed and water ad-libitum while both dehydrated and dehydrated-losartan treated groups were supplied with feed ad-libitum but no water for 20 days. Compared with time-matched controls, dehydrated camels exhibited a significant decrease in plasma levels of both ANP and BNP. Losartan-treated camels also exhibited a significant decline in ANP and BNP levels across 20 days of dehydration but the changes were not different from those seen with dehydration alone. Size exclusion high performance liquid chromatography of extracts of camel heart indicated that proB-type natriuretic peptide is the storage form of the peptide. We conclude first, that dehydration in the camel induces vigorous decrements in circulating levels of ANP and BNP; second, blockade of the renin-angiotensin system has little or no modulatory effect on the ANP and BNP responses to dehydration; third, proB-type natriuretic peptide is the storage form of this hormone in the heart of the one-humped camel.

Responses to dehydration in the one-humped camel and effects of blocking the renin-angiotensin system.

Our objectives were to compare the levels of circulating electrolytes, hormones, and renal function during 20 days of dehydration in camels versus the level in non-dehydrated camels and to record the effect of blocking angiotensin II AT1 receptors with losartan during dehydration. Dehydration induced significant increments in serum sodium, creatinine, urea, a substantial fall in body weight, and a doubling in plasma arginine vasopressin (AVP) levels. Plasma aldosterone, however, was unaltered compared with time-matched controls. Losartan significantly enhanced the effect of dehydration to reduce body weight and increase serum levels of creatinine and urea, whilst also impairing the rise in plasma AVP and reducing aldosterone levels. We conclude that dehydration in the camel induces substantial increments in serum sodium, creatinine, urea and AVP levels; that aldosterone levels are altered little by dehydration; that blockade of angiotensin II type 1 receptors enhances the dehydration-induced fall in body weight and increase in serum creatinine and urea levels whilst reducing aldosterone and attenuating the rise in plasma AVP.

Contrasting actions of diesel exhaust particles on the pulmonary and cardiovascular systems and the effects of thymoquinone.

BACKGROUND AND PURPOSE: Acute exposure to particulate air pollution has been linked to acute cardiopulmonary events, but the underlying mechanisms are uncertain. EXPERIMENTAL APPROACH We investigated the acute (at 4 and 18 h) effects of diesel exhaust particles (DEP) on cardiopulmonary parameters in mice and the protective effect of thymoquinone, a constituent of Nigella sativa. Mice were given, intratracheally, either saline (control) or DEP (30 µg·per mouse). KEY RESULTS At 18 h (but not 4 h) after giving DEP, there was lung inflammation and loss of lung function. At both 4 and 18 h, DEP caused systemic inflammation characterized by leucocytosis, increased IL-6 concentrations and reduced systolic blood pressure (SBP). Superoxide dismutase (SOD) activity was decreased only at 18 h. DEP reduced platelet numbers and aggravated in vivo thrombosis in pial arterioles. In vitro, addition of DEP (0.1-1 µg·mL(-1)) to untreated blood-induced platelet aggregation. Pretreatment of mice with thymoquinone prevented DEP-induced decrease of SBP and leucocytosis, increased IL-6 concentration and decreased plasma SOD activity. Thymoquinone also prevented the decrease in platelet numbers and the prothrombotic events but not platelet aggregation in vitro. CONCLUSIONS AND IMPLICATIONS: At 4 h after DEP exposure, the cardiovascular changes did not appear to result from pulmonary inflammation but possibly from the entry of DEP and/or their associated components into blood. However, at 18 h, DEP induced significant changes in pulmonary and cardiovascular functions along with lung inflammation. Pretreatment with thymoquinone prevented DEP-induced cardiovascular changes.

Evaluation of the direct systemic and cardiopulmonary effects of diesel particles in spontaneously hypertensive rats.

Recent data suggest that ultrafine pollutant particles (diameter <0.1microm) may pass from the lung into the systemic circulation. However, the systemic and cardiorespiratory effects of translocated particles are not well known. In this study, we determined the direct acute (24h) effect of the systemic administration of 0.01mg/kg and 0.02mg/kg diesel exhaust particles (DEP) on systolic blood pressure, heart rate, and both systemic and pulmonary inflammation in spontaneously hypertensive rats (SHR). Compared to the blood pressure in control group, rats exposed to DEP exhibited a dose-dependent increase in systolic blood pressure, at 0.01mg/kg (P<0.05) and 0.02mg/kg (P<0.01). Likewise, the heart rate was also dose-dependently increased at 0.01mg/kg (P:NS) and 0.02mg/kg (P<0.01) compared to control SHR. DEP exposure (0.02mg/kg) significantly elevated the number of leukocytes in blood (P<0.05), interleukin-6 (IL-6, P<0.005), tumor necrosis factor alpha (P<0.05) and leukotriene B4 (LTB4, P<0.005) concentrations in plasma. Moreover, in SHR given 0.02mg/kg, the number of platelet was significantly reduced (P<0.05), whereas the tail bleeding time was prolonged (P<0.05). Pulmonary inflammations were confirmed by the presence of a significant increase in the number of macrophages (0.02mg/kg) and neutrophils (0.01 and 0.02mg/kg) and protein contents (0.02mg/kg) in bronchoalveolar lavage (BAL) compared to saline-treated SHR. Also, IL-6 (0.01mg/kg; P<0.05 and 0.02mg/kg; P<0.01), LTB4 (0.02mg/kg; P<0.05) concentrations in BAL and the superoxide dismutase activity (0.02mg/kg; P=0.01) were significantly elevated compared to control group. We conclude that, in SHR, the presence of DEP in the systemic circulation leads not only to cardiac and systemic changes, but also triggers pulmonary inflammatory reaction involving IL-6, LTB4 and oxidative stress.