Biomedical subjects

F Feihl

Publications and source records attributed to F Feihl.

At least 19 recordsLinked to original sources

PubMed2006

[Clinical implications of central blood pressure].

The diagnosis and the treatment of hypertension are based on blood pressure readings traditionally taken at the level of the brachial artery. It is currently possible to determine central blood pressure using the aplanation tonometry technique and applying a transfer function to calculate the impact of reflecting waves on pressure prevailing in thoracic aorta. The reflected waves which reach the thoracic aorta in systole are more marked when the stiffness of the arterial wall is increased, leading to augmentation of central systolic blood pressure. Recent clinical trials have shown that, for the same decrease in peripheral blood pressure, different therapeutic strategies do not necessarily impact identically on central blood pressure. This fact might influence their ability to prevent cardiovascular complications.

Blood Pressure↗

PubMed2005

Foot skin blood flow following infrainguinal revascularization for critical lower limb ischemia.

INTRODUCTION: The aim of this study was to assess the blood flow in the feet before and after lower limb revascularization using laser Doppler imaging (LDI). METHODS: Ten patients with critical lower limb ischemia were prospectively enrolled from June to October 2004. All patients underwent successful unilateral surgical interventions including above-knee bypass, distal bypass and endarterectomy. Skin blood flow (SBF) over the plantar surface of both forefeet and heels was measured by LDI 24h before and 10 days after revascularization, expressed in perfusion units (PU), and reported as mean+/-SD. RESULTS: Measurements in the forefoot and heel were similar. Before revascularization mean SBF was significantly lower in the ischemic foot (130+/-71 PU) compared to the contralateral foot (212+/-68 PU), p<0.05. After revascularization a significant increase of the SBF in the forefoot (from 135+/-67 to 202+/-86 PU, p=0.001) and hindfoot (from 148+/-58 to 203+/-83, p=0.001) was observed on the treatment side. However, a large decrease of the SBF was seen in forefoot and hindfoot on the untreated side (from 250+/-123 PU to 176+/-83 and from 208+/-116 to 133+/-40, p=0.001, respectively). CONCLUSION: This study confirms the benefits of revascularization in patients with nonhealing foot lesions due to critical limb ischemia. A significant increase of the SBF was observed on the treatment side. However, an unexpected decrease was observed on the untreated side.

Aged↗

PubMed2005

Peroxynitrite activates ERK via Raf-1 and MEK, independently from EGF receptor and p21Ras in H9C2 cardiomyocytes.

Peroxynitrite is a potent oxidant and nitrating species proposed as a direct effector of myocardial damage in a wide range of cardiac diseases. Whether peroxynitrite also acts indirectly, by modulating cell signal transduction pathways in the myocardium, has not been investigated. Here, we examined the ability of peroxynitrite to activate extracellular signal-related kinase (ERK), a MAP kinase which has been linked with hypertrophic and anti-apoptotic responses in the heart, in cultured H9C2 cardiomyocytes. Peroxynitrite elicited a concentration- and time-dependent activation of ERK, secondary to the upstream activation of MEK 1 (ERK kinase). Activation of MEK-ERK by peroxynitrite was related to the upstream activation of Raf-1 kinase, as ERK and MEK phosphorylation were prevented by the Raf-1 inhibitor BAY43-9006. These effects of peroxynitrite were not associated with the activation of p21(Ras), known as a common signaling target of cellular oxidative stress. In contrast to ERK activation mediated by the epidermal growth factor (EGF), ERK activation by peroxynitrite was not prevented by AG1478 (EGF receptor inhibitor). Peroxynitrite acted through oxidative, but not nitrative chemistry, as ERK remained activated while nitration was prevented by the flavanol epicatechin. In addition to ERK, peroxynitrite also potently activated two additional members of the MAP kinase family of signaling proteins, JNK and p38. Thus, peroxynitrite activates ERK in cardiomyocytes through an unusual signaling cascade involving Raf-1 and MEK 1, independently from EGFR and P21(Ras), and also acts as a potent activator of JNK and p38. These results provide the novel concept that peroxynitrite may represent a previously unrecognized signaling molecule in various cardiac pathologies.

Animals↗

PubMed2005

Increased plasma levels of N-terminal brain natriuretic peptide (NT-proBNP) in type 2 diabetic patients with vascular complications.

AIMS: The plasma levels of either brain natriuretic peptide (BNP) or the N-terminal fragment of the prohormone (NT-proBNP) have recently gained extreme importance as markers of myocardial dysfunction. Patients with type 2 diabetes are at high risk of developing cardiovascular complications. This study was aimed to assess whether plasma NT-proBNP levels are at similar levels in type 2 diabetics with or without overt cardiovascular diseases. METHODS: We assayed plasma NT-proBNP in 54 type 2 diabetics, 27 of whom had no overt macro- and/or microvascular complications, while the remaining ones had either or both. The same assay was carried out in 38 healthy control subjects age and sex matched as a group with the diabetics. RESULTS: Plasma NT-proBNP was higher in diabetics (median 121 pg/ml, interquartile range 50-240 pg/ml, ) than in those without complications (37 pg/ml, 21-54 pg/ml, P<0.01). Compared with the controls (55 pg/ml, 40-79 pg/ml), only diabetics with vascular complications had significantly increased plasma NT-proBNP levels (P<0.001). In the diabetics, coronary heart disease and nephropathy (defined according to urinary excretion of albumin) were each independently associated with elevated values of plasma NT-proBNP. CONCLUSIONS: In type 2 diabetes mellitus, patients with macro- and/or micro-vascular complications exhibit an elevation of plasma NT-proBNP levels compared to corresponding patients with no evidence of vascular disease. The excessive secretion of this peptide is independently associated with coronary artery disease and overt nephropathy. The measurement of circulating NT-proBNP concentration may therefore be useful to screen for the presence of macro- and/or microvascular disease.

Blood Pressure↗

PubMed2004

[Intrauniversitary selection: a good or a bad way to identify the best medical students?].

During their first two years at the medical faculty of the University of Lausanne, selection of medical students is based on their performance in tests in basic sciences. However, this carries the risk that scientifically talented students who perhaps do not necessarily possess the personal skills to make them a good doctor are given preferential admission to the clinical semesters. This study followed a student cohort (n = 115), which had passed the first part of their state examination at the end of the third year course. The examination included an oral examination in psychosocial medicine (PSM) that tested the student's skills with regard to patient-physician communication. The PSM grade is compared with the grade achieved in the written tests in physics and physiology taken at the end of the first year of study. The findings showed that the performance achieved in the basic science examination had no predicative value for the student's future performance in the PSM test. Moreover, it was found that the type of pre-graduate degree had no major influence on the student's progress in their preclinical years of medical school.

Cohort Studies↗

PubMed2004

Similarity of cutaneous reactive hyperemia in the forearm of women with and without hyperinsulinemia.

OBJECTIVE: The present study was undertaken to assess in pre- and postmenopausal women whether obesity influences cutaneous reactive hyperemia in the forearm. DESIGN: Cross-sectional study. SUBJECTS AND METHODS: Eight lean premenopausal (age 24.6+/-3.5 y, BMI=21.9+/-1.5 kg/m(2), mean+/-1 s.d.), eight obese premenopausal (age 27.8+/-5.1 y, BMI=35.3+/-5.8 kg/m(2)), eight lean postmenopausal (age 56.1+/-8.3 y, BMI=20.2+/-2.2 kg/m(2)) and eight obese postmenopausal women (age 57.4+/-6.1 y, BMI=32.8+/-3 kg/m(2)) were included. Plasma glucose, insulin and lipid profile were determined in fasting state, and a glucose tolerance test was performed. The skin blood flow response to transient occlusion of the forearm circulation (reactive hyperemia, RH) was measured using a laser-Doppler imaging system. RESULTS: Obese women had hyperinsulinemia, suggesting that they were insulin-resistant. The magnitude of the RH was similar in postmenopausal compared to premenopausal women. Obesity did not influence this microvascular response. CONCLUSION: Obesity, which is known to be associated with impaired endothelial-dependent vasodilation in the skeletal musculature, has no effect on the RH of the forearm skin microcirculation.

Adult↗

PubMed2001

Protective effects of hypercapnic acidosis on ventilator-induced lung injury.

To investigate whether respiratory acidosis modulates ventilator-induced lung injury (VILI), we perfused (constant flow) 21 isolated sets of normal rabbit lungs, ventilated them for 20 min (pressure controlled ventilation [PCV] = 15 cm H(2)O) (Baseline) with an inspired CO(2) fraction adjusted for the partial pressure of CO(2) in the perfusate (PCO(2) approximately equal to 40 mm Hg), and then randomized them into three groups. Group A (control: n = 7) was ventilated with PCV = 15 cm H(2)O for three consecutive 20-min periods (T1, T2, T3). In Group B (high PCV/normocapnia; n = 7), PCV was given at 20 (T1), 25 (T2), and 30 (T3) cm H(2)O. The targeted PCO(2) was 40 mm Hg in Groups A and B. Group C (high PCV/hypercapnia; n = 7) was ventilated in the same way as Group B, but the targeted PCO(2) was approximately equal to 70 to 100 mm Hg. The changes (from Baseline to T3) in weight gain (Delta WG: g) and in the ultrafiltration coefficient (Delta K(f) = gr/min/ cm H(2)O/100g) and the protein and hemoglobin concentrations in bronchoalveolar lavage fluid (BALF) were used to assess injury. Group B experienced a significantly greater Delta WG (14.85 +/- 5.49 [mean +/- SEM] g) and Delta K(f) (1.40 +/- 0.49 g/min/cm H(2)O/100 g) than did either Group A (Delta WG = 0.70 +/- 0.43; Delta K(f) = 0.01 +/- 0.03) or Group C (Delta WG = 5.27 +/- 2.03 g; Delta K(f) = 0.25 +/- 0.12 g/min/cm H(2)O/ 100 g). BALF protein and hemoglobin concentrations (g/L) were higher in Group B (11.98 +/- 3.78 g/L and 1.82 +/- 0.40 g/L, respectively) than in Group A (2.92 +/- 0.75 g/L and 0.38 +/- 0.15 g/L) or Group C (5.71 +/- 1.88 g/L and 1.19 +/- 0.32 g/L). We conclude that respiratory acidosis decreases the severity of VILI in this model.

Acidosis, Respiratory↗

PubMed2001

Cardiovascular effects of fentanyl in conscious rats.

The polymicrobial sepsis induced by cecal ligation and puncture (CLP) in the rat is widely used in shock research. For ethical reasons, narcotic analgesics are often administered in this model, with the potential risk of confounding effects. In conscious non-septic rats, we investigated the cardiovascular effects of a continuous i.v. infusion of fentanyl (20 microg/kg per h) administered with fluid loading (10 ml/kg per h) for 24 h, a regimen commonly applied in rat CLP. Animals were randomly allocated to receive analgesia with fluid loading (Fentanyl group), or fluid loading alone (Control). All endpoints were assessed after 24 h of infusion. At that time, Control animals had mild respiratory alkalosis, which was essentially abolished by fentanyl. Analgesia mildly elevated the plasma norepinephrine levels [median (interquartile range): Control 232 pg/ml (0-292), Fentanyl 302 pg/ml (234-676), P=0.045] but was devoid of any effect on blood pressure, heart rate, cardiac output (mean +/-SD: Control 388+/-61 ml/kg per min, Fentanyl 382+/-62 ml/kg per min, P=0.87) and indices of left ventricular function derived from high-fidelity recordings of left ventricular pressure (dP/dtmax: Control 11782+/-2324 mmHg/s, Fentanyl 12107+/-2816 mmHg/s, P=0.77). In ex vivo experiments carried out immediately after animal sacrifice, no differences were noted between the Control and Fentanyl groups in the sensitivity of endothelium-intact aortic rings to norepinephrine-induced vasoconstriction (-logEC50: Control 8.78+/-0.28, Fentanyl 8.83+/-0.26, P=0.52) or acetylcholine-induced vasodilatation (-logEC50: Control 7.00+/-0.37, Fentanyl 7.06+/-0.26+/-0.53, P=0.75). In conclusion, the present data provide no contraindication, and even some support for the ethical use of a high dose i.v. infusion of fentanyl in cardiovascular studies of conscious catheterized rats undergoing CLP or other painful procedures.

Acetylcholine↗

PubMed2001

Is nitric oxide overproduction the target of choice for the management of septic shock?

Sepsis is a heterogeneous class of syndromes caused by a systemic inflammatory response to infection. Septic shock, a severe form of sepsis, is associated with the development of progressive damage in multiple organs, and is a leading cause of patient mortality in intensive care units. Despite important advances in understanding its pathophysiology, therapy remains largely symptomatic and supportive. A decade ago, the overproduction of nitric oxide (NO) had been discovered as a potentially important event in this condition. As a result, great hopes arose that the pharmacological inhibition of NO synthesis could be developed into an efficient, mechanism-based therapeutic approach. Since then, an extraordinary effort by the scientific community has brought a deeper insight regarding the feasibility of this goal. Here we present in summary form the present state of knowledge of the biological chemistry and physiology of NO. We then proceed to a systematic review of experimental and clinical data, indicating an up-regulation of NO production in septic shock; information on the role of NO in septic shock, as provided by experiments in transgenic mice that lack the ability to up-regulate NO production; effects of pharmacological inhibitors of NO production in various experimental models of septic shock; and relevant clinical experience. The accrued evidence suggests that the contribution of NO to the pathophysiology of septic shock is highly heterogeneous and, therefore, difficult to target therapeutically without appropriate monitoring tools, which do not exist at present.

Animals↗

PubMed2001

Beta-blockade with nebivolol enhances the acetylcholine-induced cutaneous vasodilation.

Nebivolol is a selective beta(1)-adrenoceptor blocker that has a vasorelaxant activity thought to be the result of a facilitation of the release of nitric oxide from the endothelium. This study was undertaken in 12 healthy male volunteers to assess whether this compound increases the vasodilatory response to acetylcholine when administered orally at a dose commonly recommended for the treatment of cardiovascular diseases. The subjects were randomly allocated to an 8-day treatment with nebivolol (5 mg once a day) and atenolol (50 mg once a day) according to a cross-over design. The two treatments were separated by a 1-week washout period. On the first and the last day of each treatment phase, both before drug administration and 3 hours after drug administration, the forearm skin blood flow response to acetylcholine applied by iontophoresis was determined with the use of a laser Doppler scanner imaging system. The reactivity to acetylcholine was significantly increased 3 hours after the administration of nebivolol on both the first and the last day of treatment, whereas atenolol had no effect on this parameter. These data therefore indicate that nebivolol, but not atenolol, enhances the vasorelaxant activity of acetylcholine in the skin vascular bed; this is compatible with a facilitation by this beta-blocker of the endothelium-dependent vasodilation.

Acetylcholine↗

PubMed2001

Diabetes and hypertension.

The incidence of hypertension is increased in individuals with diabetes mellitus. This is especially true in patients with type 2 diabetes. In these patients high blood pressure is common at the time of diagnosis of diabetes, but the development of diabetes is often preceded by a period during which hyperinsulinemia and insulin resistance is already present. Diabetes represents by itself a major risk of cardiovascular morbidity and mortality. This risk is considerably enhanced by the co-existence of hypertension. One of the main complications of type 2 diabetes is nephropathy, which manifests initially by microalbuminuria, then by clinical proteinuria, leading to a progressive chronic renal failure and end-stage renal disease. Microalbuminuria is considered today as an indicator of renal endothelial dysfunction as well as an independent predictor of the cardiovascular risk. During recent years a number of studies have shown that tight blood pressure control is essential in diabetic patients in order to provide maximal protection against cardiovascular events and the deterioration of renal function. Of note, there is recent evidence indicating that blockade of the renin-angiotensin system with angiotensin II antagonists has marked nephroprotective effects in patients with hypertension and type 2 diabetes, both at early and late stages of renal disease.

Antihypertensive Agents↗

PubMed2001

Does the activation of poly (ADP-ribose) synthetase mediate tissue injury in the sepsis induced by cecal ligation and puncture?

Poly (ADP-ribose) synthetase (PARS) is a DNA protective enzyme activated by single-strand breakage. It is suspected that exaggerated PARS activation related to biochemical stress by reactive oxygen and nitrogen species contributes to cellular injury in sepsis. The main hypothesis is that PARS activation leads to massive ATP and NAD consumption and consequent cellular energy depletion. The PARS inhibitor 3-amino-benzamide (3AB) is protective in rodents challenged with either endotoxin or intraperitoneal zymozan. The present experiment was designed to test the effect of 3AB in a more clinically relevant model of sepsis, namely polymicrobial sepsis induced by cecal ligature and puncture (CLP). Adult male Wistar rats were anesthetized, instrumented with catheters in the jugular vein and in the carotid artery, and then randomized into three groups: Sham (no laparotomy, n = 13), CLP (n = 15), and CLP/3AB (n = 18). All animals were allowed to recover and they received a continuous intravenous infusion of saline (20 mL/kg/h) and fentanyl (20 microg/kg/h). 3AB was administered to the CLP/3AB group as an intravenous bolus (10 mg/kg) followed by a continuous intravenous infusion (10 mg/kg/h). After 24 h, blood was drawn for the determination of biological indicators of organ injury. Rats were then anesthetized and biopsies of the liver were quickly frozen into liquid nitrogen for the subsequent determination of NAD and ATP levels. Further organ samples were collected for the assay of myeloperoxidase (MPO) to indicate tissue infiltration by leukocytes, and nitrotyrosine to indicate the level of biochemical stress by reactive nitrogen species. Twenty-four-hour mortality was 0/13 (Sham), 1/15 (CLP), and 5/18 (CLP/3AB; p = NS). In the surviving rats, CLP induced a clear elevation of liver enzymes, bilirubin, and pancreatic lipase, but not creatinine in the plasma, as well as a marked increase of MPO activity in liver, jejunum, and lung, but not kidney or heart. None of these variables was affected by treatment with 3AB. Furthermore, CLP did not cause depletion of NAD or ATP in the liver, nor any change in the nitrotyrosine content of any organ. These data argue against a general role of PARS activation in the pathogenesis of sepsis-induced tissue injury.

Adenosine Triphosphate↗

PubMed2000

Reproducibility of laser Doppler imaging of skin blood flow as a tool to assess endothelial function.

Endothelial dysfunction might be an important and early event in the pathogenesis of major cardiovascular diseases. Therefore, the evaluation of endothelial function in humans may be of great clinical relevance. Usual methods for that purpose are either invasive and/or technically demanding. In the dermal microcirculation, endothelial function may be assessed noninvasively from the laser Doppler measurement of increases in blood flow after either the transdermal application of acetylcholine by iontophoresis, or the release of transient arterial occlusion (reactive hyperemia). An endothelium-independent response may be provided by the iontophoresis of sodium nitroprusside. This approach is notable for technical simplicity, but of uncertain reproducibility. Sixteen young, healthy, nonsmoking males were examined in the fasting state. Changes in skin blood flow were measured with a laser Doppler imager during the iontophoresis of acetylcholine and sodium nitroprusside, as well as during reactive hyperemia, on two different days, at each of two different sites on the volar face of the forearm. Nonspecific effects related to the stimulation of terminal nerve fibers by the iontophoretic current were suppressed by prior surface anesthesia. The iontophoresis of acetylcholine and sodium nitroprusside induced a seven- to eightfold increase in dermal blood flow. The corresponding figure for peak reactive hyperemia was approximately fourfold. The mean coefficients of variation of responses recorded on different days, on the same site, in the same individual were <10% for iontophoresis of acetylcholine and for peak reactive hyperemia, and between 10 and 20% for iontophoresis of sodium nitroprusside. This day-to-day variation was significantly smaller than the site-to-site variation (p < 0.01 for all three responses). Endothelium-dependent and -independent responses of dermal blood flow evaluated with laser Doppler imaging are highly reproducible from day to day, at least in healthy nonsmoking young male subjects, and provided some simple precautions are observed, foremost among which is the strict standardization of the recording site. These observations may have implications for the testing of endothelial function in clinical studies.

Acetylcholine↗

PubMed2000

Tissue oxygenation and hemodynamic response to NO synthase inhibition in septic shock.

The objective of the study was to evaluate the tissue oxygenation and hemodynamic effects of NOS inhibition in clinical severe septic shock. Eight patients with septic shock refractory to volume loading and high level of adrenergic support were prospectively enrolled in the study. Increasing doses of NOS inhibitors [N(G)-nitro-L-arginine-methyl ester (L-NAME) or N(G)-monomethyl-L-arginine (L-NMMA)] were administered as i.v. bolus until a peak effect = 10 mmHg on mean blood pressure was obtained or until side effects occurred. If deemed clinically appropriate, a continuous infusion of L-NAME was instituted and adrenergic support weaning attempted. The bolus administration of NOS inhibitors transiently increased mean blood pressure by 10 mm Hg in all patients. Seven out of eight patients received an L-NAME infusion, associated over 24 h with a progressive decline in cardiac index (P < 0.001) and an increase in systemic vascular resistance (P < 0.01). Partial or total adrenergic support weaning was rapidly possible in 6/8 patients. Oxygen transport decreased (P < 0.001), but oxygen consumption remained unchanged in those patients in whom it could be measured by indirect calorimetry (5/8). Blood lactate and the difference between tonometric gastric and arterial PCO2 remained unchanged. There were 4/8 ICU survivors. We conclude that nitric oxide synthase inhibition in severe septic shock was followed with a progressive correction of the vasoplegic hemodynamic disturbances with finally normalization of cardiac output and systemic vascular resistances without any demonstrable deterioration in tissue oxygenation.

Adrenergic Agonists↗

PubMed2000

Permissive hypercapnia impairs pulmonary gas exchange in the acute respiratory distress syndrome.

Current recommendations for mechanical ventilation in the acute respiratory distress syndrome (ARDS) include the use of small tidal volumes (VT), even at the cost of respiratory acidosis. We evaluated the effects of this permissive hypercapnia on pulmonary gas exchange with the multiple inert gas elimination technique (MIGET) in eight patients with ARDS. After making baseline measurements, we induced permissive hypercapnia by reducing VT from 10 +/- 2 ml/kg to 6 +/- 1 ml/kg (mean +/- SEM) at constant positive end-expiratory pressure. After restoration of initial VT, we infused dobutamine to increase cardiac output (Q) by the same amount as with hypercapnia. Permissive hypercapnia increased Q by an average of 1.4 L. min(-)(1). m(2), decreased arterial oxygen tension from 109 +/- 10 mm Hg to 92 +/- 11 mm Hg (p < 0.05), markedly increased true shunt (Q S/Q T), from 32 +/- 6% to 48 +/- 5% (p < 0.0001), and had no effect on the dispersion of VA/Q.VA/Q. On reinstatement of baseline V T with maintenance of a high Q, Q S/Q T remained increased, to 38 +/- 6% (p < 0.05), and Pa(O(2 ))remained decreased, to 93 +/- 4 mm Hg (p < 0. 05). These results agreed with effects of changes in VT and Q predicted by the mathematical lung model of the MIGET. We conclude that permissive hypercapnia increases pulmonary shunt, and that deterioration in gas exchange is explained by the combined effects of increased Q and decreased alveolar ventilation.

Adolescent↗

PubMed2000

[Volume expansion during septic shock].

At its very early phase, septic shock is characterized by severe hypovolemia related to abundant fluid losses, increased venous compliance and maldistribution of extracellular fluid (interstitial edema, splanchnic pooling). It results in a drop in venous return and cardiac output. Volume expansion, with crystalloids or colloids produces a hyperdynamic state with high cardiac output and low peripheral resistances. The quantity of liquid administered rather than its composition is the main determinant. Clinical examination and hemodynamic monitoring (Swan-Ganz catheter) appear to provide the most useful criteria to assess the limits of liquid administration. Better understanding in the mechanisms of circulatory dysfunction due to the inflammation cascades might soon lead to a new approach in fluid therapy.

Blood Volume↗

PubMed1999

Hypoxic contraction of small pulmonary arteries from normal and endotoxemic rats: fundamental role of NO.

The present study was aimed at examining the role of nitric oxide (NO) in the hypoxic contraction of isolated small pulmonary arteries (SPA) in the rat. Animals were treated with either saline (sham experiments) or Escherichia coli lipolysaccharide [LPS, to obtain expression of the inducible NO synthase (iNOS) in the lung] and killed 4 h later. SPA (300- to 600-micrometer outer diameter) were mounted as rings in organ chambers for the recording of isometric tension, precontracted with PGF2alpha, and exposed to either severe (bath PO2 8 +/- 3 mmHg) or milder (21 +/- 3 mmHg) hypoxia. In SPA from sham-treated rats, contractions elicited by severe hypoxia were completely suppressed by either endothelium removal or preincubation with an NOS inhibitor [NG-nitro-L-arginine methyl ester (L-NAME), 10(-3) M]. In SPA from LPS-treated rats, contractions elicited by severe hypoxia occurred irrespective of the presence or absence of endothelium and were largely suppressed by L-NAME. The milder hypoxia elicited no increase in vascular tone. These results indicate an essential role of NO in the hypoxic contractions of precontracted rat SPA. The endothelium independence of HPV in arteries from LPS-treated animals appears related to the extraendothelial expression of iNOS. The severe degree of hypoxia required to elicit any contraction is consistent with a mechanism of reduced NO production caused by a limited availability of O2 as a substrate for NOS.

Animals↗

PubMed1998

Nonselective versus selective inhibition of inducible nitric oxide synthase in experimental endotoxic shock.

The effects of two nitric oxide synthase (NOS) inhibitors with different isoform selectivity were compared in a murine model of endotoxemia. Mice challenged with 70 mg/kg intraperitoneal (ip) lipopolysaccharide (LPS) were treated 6 h after LPS with either NG-gamma-L-arginine methyl ester (L-NAME, nonselective NOS inhibitor, 10-60 mg/kg), L-canavanine (selective inhibitor of inducible NOS, 50-300 mg/kg), or saline (0.2 mL) given ip. In a subset of mice, plasma concentrations of nitrate (NO breakdown product), lipase (pancreas injury), lactate dehydrogenase, and transaminases (liver injury) were measured 16 h after LPS. Although both inhibitors reduced plasma nitrate, they produced contrasting effects on survival and organ injury. L-NAME enhanced liver damage and tended to accelerate the time of death, while L-canavanine significantly reduced mortality and had no deleterious effects in terms of organ damage. These results indicate that nonselective NOS inhibitors are detrimental in endotoxic shock and support the potential usefulness of selective inducible NOS inhibitors in this setting.

Animals↗