Brown Norway rat ovalbumin-specific immunoglobulin E antibodies increase the human basophil expression of CD63 marker.

Anaphylactic shock is an immunoglobulin E (IgE)-dependent hypersensitivity. Biological tests like leucocyte histamine release (LHR) and human basophil activation (HBA), frequently used in human allergy, reflect both the amount of IgE fixed on cells and the cellular reactivity. To assess whether serum-specific IgE from Brown Norway (BN) rats prepared for ovalbumin (OVA)-induced anaphylactic shocks can activate human basophils which has a potential interest in experimental allergy: such a test could rapidly assert an IgE sensitization in laboratory animals genetically T-helper 2 (Th2)-predisposed. Rats (n = 39) were immunized three times (day 0, day 5 and day 21) with OVA injected subcutaneously. One week after the third immunization, a shock was induced with an intravenous (i.v.) bolus of OVA. Sensitization was assessed by passive cutaneous anaphylaxis (PCA) test and dosages of serum IgE antibodies anti-OVA by enzyme-linked immunosorbent assay. Blood basophils were counted before and during the shock. Before the shock induction (at day 21), an LHR test was performed on rat blood, and human basophils were sensitized with rat sera. HBA was demonstrated by the increase in the percentage of cells expressing CD63 antigen membrane, measured by flow cytometry. Twenty-one days after the first subcutaneous (s.c.) immunization, the rat serum induced a significant HBA. HBA was observed neither with the same serum previously heated nor with the serum from nonimmunized rats (NIRs). OVA-specific IgEs were significantly increased in immunized rat (IR) serum. The PCA test was negative when the serum was previously heated (56 degrees C). We never observed any circulating basophils, and LHR test was negative. After OVA i.v. administration, all IRs died rapidly. HBA testing strongly suggests a mediation by specific IgE in the increase of CD63 in BN rats. Thus, HBA test seems useful in assessing whether an experimental allergy was induced in animals genetically predisposed to an immune response, Th2-mediated, like BN rat. We also conclude that rat basophil activation does not participate in the histamine release during anaphylactic shock in sensitized BN rats.

Renal handling of salt and water in humans during exercise with or without hydration.

Plasma sodium (Na+) concentration, i.e. natraemia, results from body tonicity equilibrium. During exercise, a change in body tonicity can result from an imbalance between intake and loss of Na+, potassium (K+) and water (H2O) due to renal and/or extra-renal mechanisms. Whether exercise-induced changes in kidney function could be responsible for such an imbalance was studied by measuring glomerular filtration rate (creatinine clearance), proximal tubule activity (lithium clearance) and renal handling of Na+ and K+ at rest and during exercise. Since hyponatraemia during or after exercise has been reported, we also investigated whether a water load could be appropriately excreted during exercise. Ten young men pedalled on a cycle ergometer at 60% of maximal oxygen uptake for 45 min with (HE, hydrated exercise) or without (DHE, dehydrated exercise) a supply of water. In both conditions, creatinine, lithium, and electrolyte (Na+ + K+) clearances decreased and natraemia did not change. The DHE induced a loss of body mass (-1.29%), decreased diuresis and large extra-renal water loss [mean (SEM)] [880 (73) ml]. The HE led to no loss in body mass, increased diuresis and lower extrarenal water loss [680 (48) ml]. Electrolyte-free water excretion, negative for DHE, represented 60% of diuresis during HE. Thus the kidney, by increasing electrolyte reabsorption mainly in the proximal tubule, and appropriately excreting a water load, seems efficacious in regulating extracellular fluid volume and body tonicity and so not responsible for the imbalance between (Na+ + K+)/H2O intake and loss. Therefore, extra-renal changes could be the main causes of exercise-induced tonicity imbalances which could ultimately lead to dysnatraemia.

[A new concept to explain dysnatremia: the tonicity balance of entries and exits]. / Un nouveau concept pour expliquer les dysnatrémies: le bilan de la tonicité des entrées et des sorties.

Plasma sodium concentration, or natremia, results from three main factors: exchangeable sodium (Na+), exchangeable potassium (K+) and total body water (H2O). Its alterations often imply a change in cell volume. Understanding dysnatremias is essential for the treatment and prevention of hydromineral disorders. Extra-cellular fluid tonomoles consist almost exclusively of Na+ salts. Their dilution is the tonicity. K+ is an essential tonomole for intra-cellular fluid tonicity. The balance between intra and extracellular tonicities depends on water movements and is responsible for changes in intra- and extracellular fluid volumes. Cell volume is therefore depending on the tonicity balance. A change in body tonicity (which is not osmolality) can be correctly and rapidly appreciated by measuring the (Na+ + K+) and H2O balances. Clinical cases emphasize the misleadings resulting from the free-water clearance calculation or the only measurements of urinary losses. They also demonstrate that tonicity balance provides indications for therapy whereas analyses based upon electrolyte-free water do not. Intakes should be quantified with the same care than losses. The units used must be coherent to allow a quick and easy understanding at the bedside. Tonicity balance should be taught and Na+ + K+ and H2O balances should be routinely utilized by practitioners, dieticians and nurses in the concerned pediatrics, in particular intensive care, internal medicine, nephrology, pediatry and anesthesiology.

Tonicity balance, and not electrolyte-free water calculations, more accurately guides therapy for acute changes in natremia.

The usual way to decide why hyponatremia or hypernatremia has developed and to plan goals for its therapy is to analyze events in electrolyte-free water (EFW) terms. We shall demonstrate that an EFW balance does not supply this information. Rather, one must calculate mass balances for water and sodium plus potassium separately (a tonicity balance) to understand the basis for the change in natremia and the proper goals for its therapy. These points are illustrated with a clinical example.

Comparison of systemic and regional effects of dobutamine and dopexamine in norepinephrine-treated septic shock.

OBJECTIVES: To compare the effects of dobutamine and dopexamine on systemic hemodynamics, lactate metabolism, renal function and the intramucosal-arterial PCO(2) gap in norepinephrine-treated septic shock. DESIGN: A prospective, interventional, randomized clinical trial. SETTING: Adult medical/surgical intensive care unit in a university hospital. PATIENTS: After volume resuscitation, 24 patients were treated with norepinephrine alone titrated to obtain a mean arterial pressure of 75 mmHg and a cardiac index greater than 3. 5 l/min(-1). m(-2). INTERVENTIONS: Patients were randomized to receive an infusion of dobutamine (n = 12) (5 microg/kg per min) or dopexamine (n = 12) (1 microg/kg per min). MEASUREMENTS AND MAIN RESULTS: Baseline measurements included: hemodynamic parameters, renal parameters (diuresis, creatinine clearance and urinary sodium excretion), gastric mucosal-arterial PCO(2) gap, arterial and mixed venous gases and arterial lactate and pyruvate levels. These measurements were repeated after 1 (H(1)), 4 (H(4)) and 24 (H(24)) h. No difference was found between dobutamine and dopexamine among H(0) and H(1), H(4) and H(24) values for hemodynamics. Dobutamine and dopexamine at low doses had no significant effect on mean arterial pressure, heart rate, cardiac index, oxygen delivery, oxygen consumption and pulmonary artery occlusion pressure. No patients developed arrhythmia or electrocardiographic signs of myocardial ischemia. After 4 and 24 h lactate concentration decreased in the dobutamine group from 2.4 +/- 1 mmol/l to 1.7 +/- 0. 7 mmol/l and 1.5 +/- 0.4 mmol/l, respectively, while it increased in the dopexamine group from 2.3 +/- 1 mmol/l to 2.7 +/- 1 mmol/l after 4 h and returned to baseline values after 24 h (2.2 +/- 0.6). After 24 h the lactate/pyruvate ratio decreased in the dobutamine group from 15 +/- 5 to 12 +/- 3 (p < 0.05) while it was unchanged in the dopexamine group (from 16 +/- 6 to 17 +/- 4). Arterial pH increased in the dobutamine group from 7.35 +/- 0.05 to 7.38 +/- 0.07 (p < 0. 05) while it was unchanged in the dopexamine group (from 7.34 +/- 0. 01 to 7.35 +/- 0.10). The PCO(2) gap decreased after 1 and 4 h in both the dobutamine and dopexamine groups (p < 0.05 with respect to baseline). When looking at individual responses, however, patients from both groups exhibited an increased gastric PCO(2) gap. No difference was found between dobutamine and dopexamine for renal parameters. CONCLUSIONS: In norepinephrine-treated septic shock, low doses of neither dobutamine nor dopexamine caused significant effects on systemic hemodynamics and renal function and both dobutamine and dopexamine inconsistently improved the PCO(2) gap. The present results support the need for individual measurement of the effects of catecholamine on the PCO(2) gap.

Beneficial effects of L-canavanine, a selective inhibitor of inducible nitric oxide synthase, on lactate metabolism and muscle high energy phosphates during endotoxic shock in rats.

Overproduction of NO by an inducible NO synthase (iNOS) plays a role in the pathophysiology of septic shock. In such situations, NOS inhibition might be of therapeutic value, although detrimental side effects possibly related to inhibition of constitutive NOS have been reported. The use of L-canavanine, a selective inhibitor of iNOS, might be more suitable. The aim of the study was to compare in a rodent endotoxic shock the effects of saline (2 mL/h), N(G)-methyl-L-arginine(L-NMMA) (10 mg/kg/h) and L-canavanine (100 mg/kg/h) on muscle intracellular pH (pHi) and intracellular bioenergetic patterns (ATP, phosphocreatine/inorganic phosphate ratio) using in vivo 31P magnetic resonance spectroscopy (31P MRS). Three groups of anesthetized, mechanically ventilated and paralyzed rats received an intravenous infusion of 15 mg/kg of endotoxin. A fourth time-matched control group (n = 8) received 2 mL/h of saline. Mean arterial pressure, femoral blood flow, arterial blood gases, lactate, nitrate level, and 31P nuclear magnetic resonance (31P MRS) measurements were acquired at onset (T = 0), 90 min (T = 90), and 180 min (T180) after the endotoxin challenge. Femoral oxygen delivery was calculated as the product of femoral blood flow (mL/min) and arterial oxygen content. Endotoxin induced a marked decrease in arterial pressure and femoral oxygen delivery and an increase in lactate level. Intracellular pH and phosphocreatine/inorganic phosphate ratio decreased. ATP level did not change. Both L-NMMA and L-canavanine reversed the endotoxin-induced decrease in arterial pressure. L-NMMA attenuated the decrease in femoral oxygen delivery and the increase in lactate level while these were corrected by L-canavanine. Considering 31P MRS derived bioenergetic indices, the endotoxin-induced decrease in pHi and Pcr/Pi was attenuated by L-NMMA and corrected by L-canavanine. In conclusion, in a rodent model of endotoxinic shock, the continuous infusion of L-canavanine, a selective iNOS inhibitor, improved the systemic hemodynamic parameters and the intracellular bio-energetic patterns estimated by in vivo 31P MRS. To the contrary, the continuous infusion of both constitutive and inducible NOS inhibitor L-NMMA was not followed by the same achievement.

Variations in plasma sodium concentration in post-operative patients depend on an electrolyte-free water balance, part of a tonicity balance.

BACKGROUND: There is an inverse relationship between changes in the concentration of sodium in plasma (PNa) and intracellular fluid (ICF) volume. Intakes and losses of sodium (Na), potassium (K) and water can be divided into two volumes: isotonic and electrolyte-free water (EFW). Calculations of these volumes assess a tonicity balance, a tonicity imbalance results in a change of PNa: when EFW is added to body fluids, PNa decreases. Moreover, the concept of EFW permits a good understanding of the renal contribution to the defence of body tonicity. PURPOSE: To illustrate that the measurement of a tonicity balance provides the best estimate of changes in PNa in an ICU setting. METHODS: Twenty-two patients were admitted to the Post-Operative Intensive Care Unit. We investigated how well changes in EFW balance correlated with PNa variations and what is the best formula to calculate EFW in this setting. RESULTS: PNa changes depend on EFW balance; there is no significant relationship with other classical factors such as urinary osmolality or Na-free water. CONCLUSION: The utility of a tonicity balance is demonstrated. A formula is derived facilitating at the bedside the prediction of changes in PNa following fluid therapy: PNa2 = [(PNa1.TBW) + balance (Na + K)]/[TBW + balance H2O]. PNa changes can be understood and/or modified exclusively by a careful measurement of intakes and losses of Na, K and water.

Acute hyponatremia in the perioperative period: insights into its pathophysiology and recommendations for management.

Our purpose is to review the topic of acute postoperative hyponatremia by focusing on pertinent aspects of the physiology of water and solute excretion. Four areas will be highlighted: an examination of the source of addition of electrolyte-free water, an exploration of the basis for the very large natriuresis that occurs during cerebral salt wasting following neurosurgery, possible reasons to explain why acute postoperative hyponatremia may pose a greater risk for young women [Ayus and Arieff 1996, Ayus et al. 1992, Arieff 1986, Wijdick et al. 1991], and issues related to treatment of acute hyponatremia.

[Hyponatremia, toward a logical approach: the balance of tonicity]. / Hyponatrémies, pour une attitude logique: la balance de la tonicité.

Derangements in plasma sodium concentration are best analyzed by carefully determining entries and output for water, sodium and potassium, that is, by calculating a tonicity balance. Five clinical hyponatremic examples are discussed: the beer drinker has a severe deficit in total body sodium: the elderly female patient treated with a thiazide needs to be firstly repleted in potassium; the hypertensive transplanted patient with a multidrug treatment requires an increase of the urinary electrolyte-free water which has been obtained by the oral administration of urea; the post-operative hyponatremic cases (cases 4 and 5) are complex and involve a desalination phenomenon. Close observation, repeated determinations of electrolytes in plasma, urine and entries, together with measurements of water input and output, will allow the tonicity balance of the patient to be understood and thus occasional tragedies such as observed in cases 4 and 5 to be prevented.

Effective water clearance and tonicity balance: the excretion of water revisited.

OBJECTIVE: To demonstrate (1) that hyponatremia is usually due to an inappropriately low rate of excretion of electrolyte-free water and (2) that the measure "effective water clearance" (EWC) provides better information about renal defence of the body tonicity than does the classic measure free-water clearance, and to provide the rationale for calculating a "tonicity balance," which involves using water and sodium plus potassium intakes and their renal excretion to reveal the basis for changes in body tonicity. DESIGN: Prospective study. PARTICIPANTS: Four normal subjects with no conditions affecting excretion, 10 patients with advanced congestive heart failure (CHF) and 5 patients with the syndrome of inappropriate antidiuretic hormone secretion (SIADH). INTERVENTION: Normals and patients were administered a standard water load (20 mL per kg of body weight) during 45 minutes, and blood and urine samples were taken before, during and after the load was given. MAIN OUTCOME MEASURES: Urine and blood sodium and potassium concentrations, osmolar clearance, free-water clearance, electrolyte clearance and EWC. RESULTS: The water load was excreted rapidly by normals, more slowly by patients with CHF, and not at all by patients with SIADH. The EWC was positive in normals and those with CHF, but negative in those with SIADH. In patients with CHF, the EWC, but not the free-water clearance, helped explain why hyponatremia was corrected after the water load was given. CONCLUSIONS: In subjects with abnormal water excretion, the EWC provides the physiologic explanation for the renal role in variations in natremia. The authors propose a bedside evaluation of renal water and electrolyte handling that takes into consideration the role of urinary potassium in body tonicity. Changes in body tonicity can be explained by a "tonicity balance," a calculation in which the source and the net balance of sodium, potassium and water are considered.

What is the impact of potassium excretion on the intracellular fluid volume: importance of urine anions.

Hyponatremia is a common electrolyte abnormality that causes symptoms as a result of swelling of brain cells. We evaluated the impact of a negative balance for sodium (Na) and potassium (K) salts on the intracellular fluid (ICF) volume, emphasizing the role of anions excreted with K. Rats (N = 10) were deprived of food and water for 24 hours. They received half-isotonic saline to expand their extracellular fluid (ECF) volume by 20%; a long acting antidiuretic hormone (DDAVP) preparation was given to prevent the excretion of electrolyte-free water. The concentration of Na in plasma fell from 139 +/- 1 mM to 120 +/- 2 mM 24 hours after the infusion of hypotonic saline (P < 0.01). Since these rats had a small negative balance for water (4 +/- 1 ml), hyponatremia was due to their negative balances for Na (2.2 +/- 0.3 mmol) and K (2.2 +/- 0.1). There were negative balances for Cl (2.4 +/- 0.2 mmol) and phosphate (0.7 +/- 0.05 mmol). Despite the negative balance for NaCl, the ECF volume as assessed by 3H-inulin space was not contracted. In this model for acute hyponatremia, its basis was electrolyte loss, but the ECF volume was not contracted, suggesting that water shifted from the ICF to the ECF. Hyponatremia is associated with cell swelling only if its cause is positive water balance and/or is loss of Na from the ECF. It is critical to examine the urine anions to determine the compartment of origin of particles excreted with K and thereby whether hyponatremia will result in overall expansion or contraction of the ICF volume.

Functional renal maturation in rat neonates after prenatal exposure to furosemide.

We investigated the pattern of functional renal maturation and electrolyte handling on postnatal day 1, (PD1), day 5 (PD5), and day 12 (PD12) in rat neonates, after mothers were given furosemide during pregnancy. The drug was administered (75 mg/kg per day i.p.) on day 7-11 (organogenesis) and 14-18 (nephrogenesis) of gestation. On PD1 and PD5, there was a disturbance of the urinary concentrating ability with a hyperdiuresis and an over-stimulated ionic exchange, mainly the distal sodium reabsorption. From PD1 to PD12, a progressive functional recovery in electrolyte handling appeared. However, on PD12, when nephrogenesis was achieved, the renal concentrating defect remained. We discuss the possibility of a drug-induced delay in the development of the loop of Henle, leading to functional and morphological adaptations of already developed parts of the nephron.

Urea recycling: an aid to the excretion of potassium during antidiuresis.

Urea absorption in the inner medullary collecting duct provides a mechanism to elevate the concentration of urea in the papillary interstitial fluid and thereby permit the excretion of urea with as little water as possible. Urea reabsorption may have another important effect - to aid in the excretion of potassium (K). K excretion depends on two processes: first, factors such as aldosterone which cause the concentration of K in the luminal fluid of the cortical distal nephron to be high and, second, factors which augment the flow rate through those nephron segments. Since, the osmolality of the luminal fluid in the cortical collecting duct (CCD) and plasma are equal when antidiuretic hormone acts, the flow rate in the CCD is dependent on solute delivery. Urea is a major solute in the lumen of the CCD and thereby plays an important role in maintaining the CCD flow rate. Since urea and K are often found in the same foods, having urea help the excretion of K is potentially advantageous. If the excretion of urea was low, the flow rate in the terminal CCD would decline. In this circumstance, the luminal K concentration would have to rise in proportion to the fall in flow rate or there would be a diminished rate of excretion of K and, possibly, hyperkalemia.

Transplacental effects of gentamicin on endocytosis in rat renal proximal tubule cells.

Changes in kidney maturation in utero have been reported after gentamicin administration to pregnant rats. While the proteinuria commonly observed could be related to modifications of the glomerular basement membrane, perturbed renal protein handling could be accounted for by changes in the proximal tubular cells. Therefore, we studied the effect of gentamicin on the renal handling and transport of proteins in proximal tubular cells using the horseradish peroxidase, a fluid-phase marker, as a probe. Gentamicin was administered intraperitoneally to pregnant Wistar rats (75 mg/kg body weight per day) and neonatal kidneys were studied 1 day after birth. In proximal tubular cells of the deep cortical area, containing the fully matured nephrons of neonates, the transport and digestion of reabsorbed peroxidase was considerably reduced compared with controls where peroxidase reached lysosomes after endocytosis. Urinary protein excretion increased in treated animals. We conclude that gentamicin, entering the proximal tubular cells via the endocytic pathway, decreases the tubular reabsorption of proteins, thus increasing urinary protein excretion.

[Central pontine myelinolysis: apropos of an oligosymptomatic form]. / Myélinolyse centropontine: à propos d'une forme paucisymptomatique.

The authors report a case of paucisymptomatic central pontine myelinolysis (CMP). A 66 years old female had severe hypochloronatremia and hypokaliemia due to diuretic. Despite a slow hydroelectrolytic correction, she presented with dumbness and seizure. CT scan showed hypodensity of protuberance and magnetic resonance imaging (MRI) shown hypersignal of protuberance and undercortex, compatible with central and extra pontine myelinolysis. The long term clinical outcome was good, as MRI's data. Rapid and important correction of severe hyponatremia should be the most important factors of demyelination, secondary to interference with cerebral adaptation mechanisms to hypoosmolality. These factors were not present in this case.

Effects of sodium bicarbonate on striated muscle metabolism and intracellular pH during endotoxic shock.

The effects of HCO3Na load on acid-base balance and muscle intracellular bioenergetics have been investigated using 31P-magnetic resonance spectroscopy in an experimental model of endotoxinic shock. Anesthetized, mechanically ventilated, and paralyzed rats (n = 16) were given an intravenous bolus of Escherichia coli lipopolysaccharide (15 mg/kg). When shock was established they were randomly assigned to receive either HCO3Na intravenously (2 mmol/kg in 2 min) or an equimolar saline injection. Lipopolysaccharide induced a significant decrease in the levels of mean arterial pressure (58 +/- 6 vs. 120 +/- 8 mmHg), arterial pH (7.20 +/- .03 vs. 7.35 +/- .01), intracellular pH (6.86 +/- .04 vs. 7.08 +/- .01), a marked hyperlactatemia (7 +/- 3 vs. 1.2 +/- .2 mmol/L) and a drop in the phosphocreatine-inorganic phosphate ratio. In the bicarbonate-loaded rats, mean arterial pressure further decreased whereas it remained unchanged in the saline group. Bicarbonate increased arterial pH and PaCO2 transiently. In the saline group, arterial pH decreased and PaCO2 remained stable. In both groups, intracellular pH and high energy phosphates had a similar evolution. In this model of septic shock, partial correction of arterial pH using HCO3Na did not reduce the metabolic cellular injury in skeletal muscle. Based on these results, HCO3Na may be of limited therapeutic value in severe septic metabolic acidosis.

Abnormalities in histamine pharmacodynamics in chronic urticaria.

Histamine plays a key role in the pathogenesis of chronic urticaria (CU). The authors of this paper have studied the effects of ingested histamine in 25 patients with CU. A 120 mg dose of histamine, well-tolerated in the healthy subject, was instillated into the duodenum. Concomitantly, plasma histamine (H) levels and plasma and urinary methylhistamine (MH) levels were measured. Intraduodenal administration of histamine was responsible for the development of an attack of urticaria in 64% of patients, while control subjects were asymptomatic. Plasma histamine levels were significantly higher after digestive histamine challenge (DHC) in patients with CU compared with controls. An abnormal increase in plasma histamine was observed in 72% of them. Plasma MH exhibited the same kinetic behaviour with a usually delayed time-pattern. Urinary MH concentration was higher in patients presenting with early-onset urticaria during the first hour than in those with the late-onset type between 1 and 12 hr after DHC. The coefficient of methylation (plasma MH/MH+H) was not significantly different in patients presenting with an attack of urticaria following DHC and in other subjects. Urinary excretion of MH and urinary flow increased significantly in patients presenting with an attack of urticaria following DHC which corresponds to increased absorption of histamine during the 5-hr period following DHC and its role on excretion by the kidney via vasodilation which it induces. This study demonstrates the abnormal frequency of disturbances in the metabolism of exogenous histamine in patients with CU. Increased plasma H accounts for the abnormal passage of H across the intestinal barrier which can result either from intestinal hyperpermeability and/or a deficit in the enzymatic catabolism of histamine. The systems of methylation and urinary clearance of MH appear to be effective. It is thus postulated that there is a deficit in diamine oxidase (DAO) in the enterocyte. The lack of correlation between the kinetic behaviour of plasma H and the onset of urticaria draws attention to the extent of individual variability in skin reactivity to histamine.