Water Conservation Overrides Osmotic Diuresis During SGLT2 Inhibition in Patients With Heart Failure

BACKGROUND

Sodium-glucose cotransporter 2 inhibitors are believed to improve cardiac outcomes due to their osmotic diuretic potential.

OBJECTIVES

The goal of this study was to test the hypothesis that vasopressin-driven urine concentration overrides the osmotic diuretic effect of glucosuria induced by dapagliflozin treatment.

METHODS

DAPA-Shuttle1 (Hepato-renal Regulation of Water Conservation in Heart Failure Patients With SGLT-2 Inhibitor Treatment) was a single-center, double-blind, randomized, placebo-controlled trial, in which patients with chronic heart failure NYHA functional classes I/II and reduced ejection fraction were randomly assigned to receive dapagliflozin 10 mg daily or placebo (1:1) for 4 weeks. The primary endpoint was change from baseline in urine osmolyte concentration. Secondary endpoints included changes in copeptin levels and solute free water clearance.

RESULTS

Thirty-three randomized, sodium-glucose cotransporter 2 inhibitor-naïve participants completed the study, 29 of whom (placebo: n = 14; dapagliflozin: n = 15) provided accurate 24-hour urine collections (mean age 59 ± 14 years; left ventricular ejection fraction 31% ± 9%). Dapagliflozin treatment led to an isolated increase in urine glucose excretion by 3.3 mmol/kg/d (95% CI: 2.51-4.04; P < 0.0001) within 48 hours (early) which persisted after 4 weeks (late; 2.7 mmol/kg/d [95% CI: 1.98-3.51]; P < 0.0001). Dapagliflozin treatment increased serum copeptin early (5.5 pmol/L [95% CI: 0.45-10.5]; P < 0.05) and late (7.8 pmol/L [95% CI: 2.77-12.81]; P < 0.01), leading to proportional reductions in free water clearance (early: -9.1 mL/kg/d [95% CI: -14 to -4.12; P < 0.001]; late: -11.0 mL/kg/d [95% CI: -15.94 to -6.07; P < 0.0001]) and elevated urine concentrations (late: 134 mmol/L [95% CI: 39.28-229.12]; P < 0.01). Therefore, urine volume did not significantly increase with dapagliflozin (mean difference early: 2.8 mL/kg/d [95% CI: -1.97 to 7.48; P = 0.25]; mean difference late: 0.9 mL/kg/d [95% CI: -3.83 to 5.62]; P = 0.70).

CONCLUSIONS

Physiological-adaptive water conservation eliminated the expected osmotic diuretic potential of dapagliflozin and thereby prevented a glucose-driven increase in urine volume of approximately 10 mL/kg/d · 75 kg = 750 mL/kg/d. (Hepato-renal Regulation of Water Conservation in Heart Failure Patients With SGLT-2 Inhibitor Treatment [DAPA-Shuttle1]; NCT04080518).

Cardioprotective Properties of Mannitol-Involvement of Mitochondrial Potassium Channels

Cardiac preconditioning (PC) and postconditioning (PoC) are powerful measures against the consequences of myocardial ischemia and reperfusion (I/R) injury. Mannitol-a hyperosmolar solution-is clinically used for treatment of intracranial and intraocular pressure or promotion of diuresis in renal failure. Next to these clinical indications, different organ-protective properties-e.g., perioperative neuroprotection-are described. However, whether Mannitol also confers cardioprotection via a pre- and/or postconditioning stimulus, possibly reducing consequences of I/R injury, remains to be seen. Therefore, in the present study we investigated whether (1) Mannitol-induced pre- and/or postconditioning induces myocardial infarct size reduction and (2) activation of mitochondrial ATP-sensitive potassium (mKATP) channels is involved in cardioprotection by Mannitol. Experiments were performed on isolated hearts of male Wistar rats via a pressure controlled Langendorff system, randomized into 7 groups. Each heart underwent 33 min of global ischemia and 60 min of reperfusion. Control hearts (Con) received Krebs-Henseleit buffer as vehicle only. Pre- and postconditioning was achieved by administration of 11 mmol/L Mannitol for 10 min before ischemia (Man-PC) or immediately at the onset of reperfusion (Man-PoC), respectively. In further groups, the mKATP channel blocker 5HD, was applied with and without Mannitol, to determine the potential underlying cardioprotective mechanisms. Primary endpoint was infarct size, determined by triphenyltetrazolium chloride staining. Mannitol significantly reduced infarct size both as a pre- (Man-PC) and postconditioning (Man-PoC) stimulus compared to control hearts (Man-PC: 31 ± 4%; Man-PoC: 35 ± 6%, each p < 0.05 vs. Con: 57 ± 9%). The mKATP channel inhibitor completely abrogated the cardioprotective effect of Mannitol-induced pre- (5HD-PC-Man-PC: 59 ± 8%, p < 0.05 vs. Man-PC) and postconditioning (5HD-PoC-Man-PoC: 59 ± 10% vs. p < 0.05 Man-PoC). Infarct size was not influenced by 5HD itself (5HD-PC: 60 ± 14%; 5HD-PoC: 54 ± 14%, each ns vs. Con). This study demonstrates that Mannitol (1) induces myocardial pre- and postconditioning and (2) confers cardioprotection via activation of mKATP channels.

Rg1 in combination with mannitol protects neurons against glutamate-induced ER stress via the PERK-eIF2 α-ATF4 signaling pathway

AIMS

Ginseng and ginsenosides are known for their remarkable effects on the central nervous system. However, pharmacokinetic studies have suggested that the Ginsenoside Rg1 (Rg1) cannot be efficiently transported through the blood-brain barrier. To investigate the effects of Rg1 in combination with mannitol protects neurons against glutamate-induced ER stress via the PERK-eIF2 -ATF4 signaling pathway.

MAIN METHODS

Rg1, along with the BBB permeabilizer mannitol, exhibited a potent neuroprotective effect by significantly reducing the neurological scores and infarct volume in rats exposed to middle cerebral artery occlusion. We evaluated the effect of Rg1 on neuroprotection after MCAO, and also explored its potential mechanism of action.

KEY FINDINGS

Our results show that Rg1 reduced the number of terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive neurons. This neuroprotection may be dependent, at least in part, on the preservation of the endoplasmic reticulum and mitochondrial function. Ischemia-induced brain injury is largely caused by the excessive release of glutamate, which results in excitotoxicity and cell death. Neurons were pretreated with Rg1 before inducing endoplasmic reticulum stress with glutamate. A reduction in the expression of Bax and a concomitant increase in Bcl2 expression prevented the induction of apoptosis. Furthermore, Rg1 downregulated the expression of endoplasmic reticulum stress genes.

SIGNIFICANCE

Our results indicate that Rg1 modulation of stress-responsive genes helps prevent glutamate-induced endoplasmic reticulum stress in neurons through the PERK-eIF2-α-ATF4 signaling pathway.

Hypertonic saline and mannitol in patients with traumatic brain injury: A systematic and meta-analysis

BACKGROUND

To compare the effects of 3% hypertonic saline solution and 20% mannitol solution on intracranial hypertension.

METHODS

WAN-FANGDATA, CNKI, and CQVIP databases were searched, and relevant literatures of randomized controlled trials comparing 3% hypertonic saline solution with mannitol in reducing intracranial hypertension from 2010 to October 2019 were collected. Meta-analysis was performed using RevMan software.

RESULTS

As a result, 10 articles that met the inclusion criteria were finally included. A total of 544 patients were enrolled in the study, 270 in the hypertonic saline group and 274 in the mannitol group. There was no significant difference in the decrease of intracranial pressure and the onset time of drug between the 2 groups after intervention (all P > .05). There was a statistically significant difference between the hypertonic saline group and the mannitol group in terms of duration of effect in reducing intracranial pressure (95% confidence interval: 0.64-1.05, Z = 8.09, P < .00001) and cerebral perfusion pressure after intervention (95% confidence interval: 0.15-0.92, Z = 2.72, P = .007).

CONCLUSION

Both 3% hypertonic saline and mannitol can effectively reduce intracranial pressure, but 3% hypertonic saline has a more sustained effect on intracranial pressure and can effectively increase cerebral perfusion pressure.

Effects of Osmotic Therapy on Pupil Reactivity: Quantification Using Pupillometry in Critically Ill Neurologic Patients

BACKGROUND

Osmotic therapy is a critical component of medical management for cerebral edema. While up to 90% of neurointensivists report using these treatments, few quantitative clinical measurements guide optimal timing, dose, or administration frequency. Its use is frequently triggered by a qualitative assessment of neurologic deterioration and/or pupil size, and anecdotally appears to improve pupil asymmetry suggestive of uncal herniation. However, subjective pupil assessment has poor reliability, making it difficult to detect or track subtle changes. We hypothesized that osmotic therapy reproducibly improves quantitative pupil metrics.

METHODS

We included patients at two centers who had recorded quantitative pupil measurements within 2 h before and after either 20% mannitol or 23.4% hypertonic saline in the neurosciences intensive care unit. The primary outcome was the Neurologic Pupil Index (NPi), a composite metric ranging from 0 to 5 in which > 3 is considered normal. Secondary outcomes included pupil size, percent change, constriction and dilation velocity, and latency. Results were analyzed with Wilcoxon signed-rank tests, Chi-square and multi-level linear regression to control for other edema-reducing interventions.

RESULTS

Out of 72 admissions (403 paired pupil observations), NPi significantly differed within 2 h of osmotic therapy when controlling for other commonly used interventions in our whole cohort (β = 0.08, p = 0.0168). The effect was most pronounced (β = 0.57) in patients with abnormal NPi prior to intervention (p = 0.0235).

CONCLUSIONS

Pupil reactivity significantly improves after osmotic therapy in a heterogenous critically ill population when controlling for various other interventions. Future work is necessary to determine dose-dependent effects and clinical utility.

Osmotic diuresis by SGLT2 inhibition stimulates vasopressin-induced water reabsorption to maintain body fluid volume

Most of the filtered glucose is reabsorbed in the early proximal tubule by the sodium-glucose cotransporter SGLT2. The glycosuric effect of the SGLT2 inhibitor ipragliflozin is linked to a diuretic and natriuretic effect that activates compensatory increases in fluid and food intake to stabilize body fluid volume (BFV). However, the compensatory mechanisms that are activated on the level of renal tubules remain unclear. Type 2 diabetic Goto-Kakizaki (GK) rats were treated with vehicle or 0.01% (in diet) ipragliflozin with free access to fluid and food. After 8 weeks, GK rats were placed in metabolic cages for 24-hr. Ipragliflozin decreased body weight, serum glucose and systolic blood pressure, and increased fluid and food intake, urinary glucose and Na+ excretion, urine volume, and renal osmolar clearance, as well as urine vasopressin and solute-free water reabsorption (TcH2O). BFV, measured by bioimpedance spectroscopy, and fluid balance were similar among the two groups. Urine vasopressin in ipragliflozin-treated rats was negatively and positively associated with fluid balance and TcH2O, respectively. Ipragliflozin increased the renal membrane protein expression of SGLT2, aquaporin (AQP) 2 phosphorylated at Ser269 and vasopressin V2 receptor. The expression of SGLT1, GLUT2, AQP1, and AQP2 was similar between the groups. In conclusion, the SGLT2 inhibitor ipragliflozin induced a sustained glucosuria, diuresis, and natriuresis, with compensatory increases in fluid intake and vasopressin-induced TcH2O in proportion to the reduced fluid balance to maintain BFV. These results indicate that the osmotic diuresis induced by SGLT2 inhibition stimulates compensatory fluid intake and renal water reabsorption to maintain BFV.

Examining Mannitol Use in Kidney Cancer Surgery: A Cautionary Tale of Extrapolated Surgical Data

Mannitol for renal protection during partial nephrectomy is common but unsupported by evidence from clinical trials. The impact of mannitol on renal physiology includes both beneficial and harmful effects. Current understanding of renal ischemia reperfusion injury suggests potentially targetable processes that have a lower potential risk.

Phase III Trial of Intravenous Mannitol Versus Placebo During Nephron-sparing Surgery: Post Hoc Analysis of 3-yr Outcomes

Our recently reported phase III trial demonstrated that patients undergoing nephron-sparing surgery (NSS) with an estimated glomerular filtration rate (eGFR) of ≥45 ml/min/1.73 m² who received mannitol had no improvement in renal function at 6 mo compared with those who received placebo. Some authors have suggested that benefit is restricted to subgroups, such as those with comorbidities. We assessed whether preoperative eGFR, or other patient and surgical factors modified the effect of mannitol on postoperative outcomes at 6 mo and with extended follow-up. We also assessed whether mannitol was associated with differences in long-term GFR years after surgery. No significant difference between the mannitol or placebo groups (mean eGFR difference: 1.4; 95% confidence interval: -2.6, 5.3; p = 0.5) was found in the 134 patients with known eGFR at 3 yr after NSS. At both 6 mo and 3 yr, the effect of mannitol was not significantly modified by patient or surgical factors including preoperative eGFR. In summary, we validated our original trial conclusions by finding that intraoperative use of mannitol does not improve either short- or long-term renal function in patients undergoing NSS. Specifically, there is no evidence that comorbidities, including lower preoperative eGFR, modify the effect of mannitol. PATIENT SUMMARY: Use of mannitol at the time of partial nephrectomy does not improve either short- or long-term renal function even in patients with comorbidities, including lower preoperative renal function. The routine use of intraoperative mannitol should be discontinued.

Mannitol decreases neocortical epileptiform activity during early brain development via cotransport of chloride and water

Seizures and brain injury lead to water and Cl^- accumulation in neurons. The increase in intraneuronal Cl^- concentration ([Cl^-]_i) depolarizes the GABA_A reversal potential (E_GABA) and worsens seizure activity. Neocortical neuronal membranes have a low water permeability due to the lack of aquaporins necessary to move free water. Instead, neurons use cotransport of ions including Cl^- to move water. Thus, increasing the extracellular osmolarity during seizures should result in an outward movement of water and salt, reducing [Cl^-]_i and improving GABA_A receptor-mediated inhibition. We tested the effects of hyperosmotic therapy with a clinically relevant dose of mannitol (20 mM) on epileptiform activity, spontaneous multiunit activity, spontaneous inhibitory post-synaptic currents (sIPSCs), [Cl^-]_i, and neuronal volume in layer IV/V of the developing neocortex of C57BL/6 and Clomeleon mice. Using electrophysiological techniques and multiphoton imaging in acute brain slices (post-natal day 7-12) and organotypic neocortical slice cultures (post-natal day 14), we observed that mannitol: 1) decreased epileptiform activity, 2) decreased neuronal volume and [Cl^-]_i through CCCs, 3) decreased spontaneous multi-unit activity frequency but not amplitude, and 4) restored the anticonvulsant efficacy of the GABA_A receptor modulator diazepam. Increasing extracellular osmolarity by 20 mOsm with hypertonic saline did not decrease epileptiform activity. We conclude that an increase in extracellular osmolarity by mannitol mediates the efflux of [Cl^-]_i and water through CCCs, which results in a decrease in epileptiform activity and enhances benzodiazepine actions in the developing neocortex in vitro. Novel treatments aimed to decrease neuronal volume may concomitantly decrease [Cl^-]_i and improve seizure control.

Renal tubular epithelial cells injury induced by mannitol and its potential mechanism

Administration of mannitol with high dose could induce extensive isometric renal proximal tubular vacuolization and acute renal failure in clinic. We previously demonstrated that mannitol-induced human kidney tubular epithelial cell (HK-2) injury. The objective of our present work was to further study the cytotoxicity of mannitol in HK-2 cells and its potential mechanism. Cell viability was assessed by an MTT method. Cell morphological changes were observed. Furthermore, levels of malondialdehyde (MDA) and glutathione (GSH) were measured. Flow cytometry was performed to determine cell apoptosis by using Annexin V-FITC and PI. In addition, the F-actin of cells was labeled by FITC-Phalloidin for observation of cytoskeleton. The MTT assay displayed that the cell viability decreased significantly in a dose- and time-dependent manner. The morphological changes were observed, including cell membrane rapture and cell detachment. The GSH concentration in HK-2 cells decreased dramatically in mannitol treatment group, while MDA content increased significantly. The results of flow cytometry indicated that apoptotic percentages of HK-2 cells increased in 250 mmol/L mannitol treatment group. After treatment with 250 mmol/L mannitol for 48 h, HK-2 cells showed disorganization of cytoskeleton and even exhibited a totally destroyed cytoskeleton. Therefore, high dose of mannitol has a toxic effect on renal tubular epithelial cells, which might be attributed to oxidative stress, destroyed cellular cytoskeleton and subsequent cell apoptosis.

Modulation of Hyperosmotic and Immune-Induced Disruption of the Blood-Brain Barrier by the Nitric Oxide System

OBJECTIVES

The role of nitric oxide (NO) in modulating the blood-brain barrier (BBB) is not entirely clear. We examined the effect of different NO synthase (NOS) inhibitors and NO donors on the permeability of the BBB in animals with normally functioning brain blood vessels, following disruption by hyperosmotic mannitol and during immune inflammation.

METHODS

We administered L-NAME, aminoguanidine, S-methyl-thiocitrulline (SMT) and 7-indazole (NOS inhibitors) and NOR-4 (an NO donor) into the cerebral ventricle of rats. Disruption of the BBB was induced by intracarotid injection of mannitol (25%). Experimental autoimmune encephalomyelitis (EAE) was induced by brain homogenate. The extent of disruption was evaluated by Evans blue (2%) dye extravasation.

RESULTS

L-NAME (a nonspecific NOS inhibitor) and SMT (a neuronal and endothelial NOS inhibitor) increased mannitol-induced disruption of BBB. This effect was inhibited by NO donors. In animals with a normally functioning BBB, none of these inhibitors or NO donors caused a change in the permeability. 7-indazole (a specific neuronal NOS inhibitor) and aminoguanidine (an inducible NOS inhibitor) had no facilitatory effect on BBB permeability, either alone or in combination with hyperosmotic mannitol. Administration of L-NAME and SMT to rats with EAE significantly aggravated the clinical outcome. In contrast, the administration of NOR-4 diminished clinical signs of EAE.

CONCLUSION

The NOS system does not play a role in BBB permeability in naïve animals. Only endothelial NOS takes part in the facilitation of BBB compromised by mannitol and EAE. Extrinsic NO decreases this facilitatory effect.

Hypertonic saline for brain relaxation and intracranial pressure in patients undergoing neurosurgical procedures: a meta-analysis of randomized controlled trials

Background

A wealth of evidence from randomized controlled trials (RCTs) has indicated that hypertonic saline (HS) is at least as effective as, if not better than, mannitol in the treatment of increased intracranial pressure(ICP). However, there is little known about the effects of HS in patients during neurosurgery. Thus, this meta-analysis was performed to compare the intraoperative effects of HS with mannitol in patients undergoing craniotomy.

Methods

According to the research strategy, we searched PUBMED, EMBASE and Cochrane Central Register of Controlled Trials. Other sources such as the internet-based clinical trial registries and conference proceedings were also searched. After literature searching, two investigators independently performed literature screening, quality assessment of the included trials and data extraction. The outcomes included intraoperative brain relaxation, intraoperative ICP, total volume of fluid required, diuresis, hemodynamic parameters, electrolyte level, mortality or dependence and adverse events.

Results

Seven RCTs with 468 participants were included. The quality of the included trials was acceptable. HS could significantly increase the odds of satisfactory intraoperative brain relaxation (OR: 2.25, 95% CI: 1.32–3.81; P = 0.003) and decrease the mean difference (MD) of maximal ICP (MD: −2.51mmHg, 95% CI: −3.39—1.93mmHg; P<0.00001) in comparison with mannitol with no significant heterogeneity among the study results. Compared with HS, mannitol had a more prominent diuretic effect. And patients treated with HS had significantly higher serum sodium than mannitol-treated patients.

Conclusions

Considering that robust outcome measures are absent because brain relaxation and ICP can be influenced by several factors except for the hyperosmotic agents, the results of present meta-analysis should be interpreted with cautions. Well-designed RCTs in the future are needed to further test the present results, identify the impact of HS on the clinically relevant outcomes and explore the potential mechanisms of HS.

Prostaglandin E2 prevents hyperosmolar-induced human mast cell activation through prostanoid receptors EP2 and EP4

Background

Mast cells play a critical role in allergic and inflammatory diseases, including exercise-induced bronchoconstriction (EIB) in asthma. The mechanism underlying EIB is probably related to increased airway fluid osmolarity that activates mast cells to the release inflammatory mediators. These mediators then act on bronchial smooth muscle to cause bronchoconstriction. In parallel, protective substances such as prostaglandin E₂ (PGE₂) are probably also released and could explain the refractory period observed in patients with EIB.

Objective

This study aimed to evaluate the protective effect of PGE₂ on osmotically activated mast cells, as a model of exercise-induced bronchoconstriction.

Methods

We used LAD2, HMC-1, CD34-positive, and human lung mast cell lines. Cells underwent a mannitol challenge, and the effects of PGE₂ and prostanoid receptor (EP) antagonists for EP_1–4 were assayed on the activated mast cells. Beta-hexosaminidase release, protein phosphorylation, and calcium mobilization were assessed.

Results

Mannitol both induced mast cell degranulation and activated phosphatidyl inositide 3-kinase and mitogen-activated protein kinase (MAPK) pathways, thereby causing de novo eicosanoid and cytokine synthesis. The addition of PGE₂ significantly reduced mannitol-induced degranulation through EP₂ and EP₄ receptors, as measured by beta-hexosaminidase release, and consequently calcium influx. Extracellular-signal-regulated kinase 1/2, c-Jun N-terminal kinase, and p38 phosphorylation were diminished when compared with mannitol activation alone.

Conclusions

Our data show a protective role for the PGE₂ receptors EP₂ and EP₄ following osmotic changes, through the reduction of human mast cell activity caused by calcium influx impairment and MAP kinase inhibition.

Influence of environmental hypertonicity on the induction of ureogenesis and amino acid metabolism in air-breathing walking catfish (Clarias batrachus, Bloch)

Effect of environmental hypertonicity, due to exposure to 300 mM mannitol solution for 7 days, on the induction of ureogenesis and also on amino acid metabolism was studied in the air-breathing walking catfish, C. batrachus, which is already known to have the capacity to face the problem of osmolarity stress in addition to other environmental stresses in its natural habitats. Exposure to hypertonic mannitol solution led to reduction of ammonia excretion rate by about 2-fold with a concomitant increase of urea-N excretion rate by about 2-fold. This was accompanied by significant increase in the levels of both ammonia and urea in different tissues and also in plasma. Further, the environmental hypertonicity also led to significant accumulation of different non-essential free amino acids (FAAs) and to some extent the essential FAAs, thereby causing a total increase of non-essential FAA pool by 2-3-fold and essential FAA pool by 1.5-2.0-fold in most of the tissues studied including the plasma. The activities of three ornithine-urea cycle (OUC) enzymes such as carbamoyl phosphate synthetase, argininosuccinate synthetase and argininosuccinate lyase in liver and kidney tissues, and four key amino acid metabolism-related enzymes such as glutamine synthetase, glutamate dehydrogenase (reductive amination), alanine aminotransaminase and aspartate aminotransaminase were also significantly up-regulated in different tissues of the fish while exposing to hypertonic environment. Thus, more accumulation and excretion of urea-N observed during hypertonic exposure were probably associated with the induction of ureogenesis through the induced OUC, and the increase of amino acid pool was probably mainly associated with the up-regulation of amino acid synthesizing machineries in this catfish in hypertonic environment. These might have helped the walking catfish in defending the osmotic stress and to acclimatize better under hypertonic environment, which is very much uncommon among freshwater teleosts.

Hyperosmolality-mediated peritoneal microvascular vasodilation is linked to aquaporin function

Glucose-based peritoneal dialysis (PD) solutions dilate the parietal and visceral peritoneal microvasculature by endothelium-dependent mechanisms that primarily involve hyperosmolality. This PD-mediated dilation occurs by active intracellular glucose uptake and adenosine Al receptor activation, and by hyperosmolality-stimulated glibenclamide-sensitive potassium channels. Both pathways invoke NO as a second messenger for vasodilation. We hypothesized that during crystalloid-induced osmosis, the osmotic water flux through the transendothelial water-exclusive aquaporin 1 (AQP1) channels is the primary mechanism whereby the endothelium is being stimulated to instigate hyperosmolality-driven vasodilation. Four microvascular levels (diameters in the range 6 - 100 microm) were visualized by intravital videomicroscopy of the terminal ileum in anesthetized rats. Microvascular diameters and flow were measured after topical exposure to a 5% hypertonic mannitol or 2.5% glucose-based PD solution, at baseline and after brief tissue pre-treatment (with 0.1% glutaraldehyde for 10 seconds) or after combined tissue pre-treatment and pharmacologic blockade of AQP1 with HgCl2 (100 micromol/L). Vascular endothelial integrity was verified by the response to acetylcholine (10(-4) mol/L) and sodium nitroprusside (10(-4) mol/L). The hyperosmolar solutions both caused rapid and sustained vasodilation at all microvascular levels, which was not altered by tissue pre-treatment. Inhibition of AQP1 completely abolished the mannitol-induced vasodilation and markedly attenuated the PD fluid-mediated vasodilation. Neither glutaraldehyde pre-treatment nor HgCl2 affected tissue integrity or endothelial cell function. We conclude that the peritoneal microvascular vasodilation caused by hyperosmolar PD fluid is instigated by the osmotic water flux through AQP1. Clinical PD solutions have components other than hyperosmolality that can induce endothelium-dependent peritoneal microvascular vasodilation independent of the AQP1-mediated osmosis.

Cannulation of the internal carotid artery in mice: a novel technique for intra-arterial delivery of therapeutics

We have developed a novel minimally invasive technique for the intra-arterial delivery of therapeutics to the mouse brain. CD-1 mice were anesthetized and placed in a lateral decubitus position. A 10mm midline longitudinal incision was made over the thyroid bone. The omohyoid and sternomastoid muscles were retracted to expose the common carotid artery and external carotid artery (ECA). To maximize delivery of administered agents, the superior thyroid artery was ligated or coagulated, and the occipital artery and the pterygopalatine artery (PPA) were temporarily occluded with 6-0 prolene suture. The ECA was carefully dissected and a permanent ligature was placed on its distal segment while a temporary 6-0 prolene ligature was placed on the proximal segment in order to obtain a flow-free segment of vessel. A sterilized 169 μm outer diameter polyimide microcatheter was introduced into the ECA and advanced in retrograde fashion toward the carotid bifurcation. The catheter was then secured and manually rotated so that the microcatheter tip was oriented cephalad in the internal carotid artery (ICA). We were able to achieve reproducible results for selective ipsilateral hemispheric carotid injections of mannitol mediated therapeutics and/or gadolinium-based MRI contrast agent. Survival rates were dependent on the administered agent and ranged from 78 to 90%. This technique allows for reproducible delivery of agents to the ipsilateral cerebral hemisphere by utilizing anterograde catheter placement and temporary ligation of the PPA. This method is cost-effective and associated with a low rate of morbimortality.

Pulse-plethysmographic variables in hemodynamic assessment during mannitol infusion

Plethysmographic signal using pulse oximetry may be used to assess fluid status of patients during surgery as it resembles arterial pressure waveform. This will avoid placement of invasive arterial lines. This study was designed to find out whether intravascular volume changes induced by mannitol bolus in neurosurgical patients are detected by variations in arterial pressure and plethysmographic waveforms and also to assess the strength of correlation between different variables derived from these two waveforms. The time difference between the onset of arterial and plethysmographic waveforms as means of significant hemodynamic changes was also evaluated. Forty one adult ASA I and II neurosurgical patients requiring mannitol infusion were recruited. Arterial line and plethysmographic probe were placed in the same limb. Digitized waveforms were collected before, at the end, and 15, 30 and 60 min after mannitol infusion. Using MATLAB, the following parameters were collected for three consecutive respiratory cycles,-systolic pressure variation (SPV), pulse pressure variation (PPV), plethysmographic peak variation (Pl-PV), plethysmographic amplitude variation (Pl-AV) and blood pressure-plethysmographic time lag (BP-Pleth time lag). Changes in above parameters over the study period were studied using repeated measure analysis of variance. Correlation between the parameters was analysed. SPV and Pl-PV showed significant increase at 15, 30 and 60 min compared to end of mannitol infusion (P < 0.01 for SPV; P < 0.05 for Pl-PV). PPV and Pl-AV showed significant increase only at 30 min (P < 0.05). The correlation between ∆SPV-∆Pl-PV, ∆PPV-∆Pl-AV and ∆SPV-∆BP-Pleth time lag were significant (r = 0.3; P < 0.01). SPV and time lag had no significant interaction. Pl-PV correlates well with SPV following mannitol infusion and can be used as an alternative to SPV. (BP-Pleth) time-lag promises to be an important parameter in assessing the state of peripheral vascular resistance and deserves further investigation.

[Physiological analysis of various types of osmotic diuresis]

Efficacy of drugs reduced proximal reabsorption was compared in experiments with female Wistar rats. Urine flow rate for the 1st h of experiment was enhanced after polyethylene glycol-400 (PEG) and 6% Na2SO4 infusion by over 30-fold, exenatide--40-fold, glycerol--11-fold as compared with the control. The maximal values of Na+ excretion were observed during Na2SO4 and exenatide administration (280 +/- 31 micromol/h vs. 3.2 +/- 0.6 Imol/h/100 g bw). The highest K+ excretion was revealed in experiments with glycerol administration (41 +/- 5 micromol/h vs. 7 +/- 2 micromol/h/100 g bw), Mg2+ --after exenatide injection (5.3 +/- 1.3 micromol/h vs. 0.16 +/- 0.03 micromol/ h/100 g bw). Diuretic effects were additive after combined administration of maximal doses of exenatide and PEG which suggests a different mechanism of action of solutes filtrated (PEG) to the proximal nephron segment and generated due to Na+/HW-exchange inhibition (exenatide). Osmotic diuretics differ by potency, mechanism of diuretic action and selectivity of ion excretion).

Inhaled mannitol changes the sputum properties in asthmatics with mucus hypersecretion

BACKGROUND AND OBJECTIVES

Most asthmatics with mucus hypersecretion have difficulty in clearing their secretions so that mucus plugs and airway obstruction are commonly present. Inhaled mannitol facilitates clearance of mucus. This study investigated the changes in the physical properties of sputum in response to mannitol in asthmatics with chronic cough and sputum production.

METHOD

Sputum was collected from 12 asthmatics (26-73 year), lifelong non-smokers, at baseline, after eformoterol (24 mug) and after mannitol on each of four visits. Inhaled mannitol doses were: 635 mg (Visit 1), 240 mg (Visit 2), 360 mg (Visit 3) and 360 mg in the presence of montelukast (Visit 4). Eformoterol was inhaled before mannitol on each visit to prevent bronchoconstiction. Sputum measurements included viscosity, elasticity, surface tension, contact angle-glass and percentage solids.

RESULTS

There were no significant differences between the sputum properties at baseline and after eformoterol. Mannitol (360 mg) reduced the baseline (mean +/- SEM) elasticity from 29.9 +/- 4.5 to 15.1 +/- 1.4 Pa (P < 0.0001), viscosity from 18.4 +/- 3.2 to 8.1 +/- 1.2 Pa (P < 0.0001) at 1 rad/ s, surface tension from 92.1 +/- 2.2 to 81.9 +/- 2.5 mN/m (P < 0.0001), contact angle-glass from 57.5 +/- 3.2 to 49.6 +/- 2.0 degrees (P < 0.0001), and percentage solids from 6.9 +/- 0.7 to 5.7 +/- 0.4% (P < 0.0001). All doses of mannitol reduced the sputum properties similarly and no property was further reduced by montelukast (P > 0.4).

CONCLUSION

Inhaled mannitol reduced the viscoelasticity, surface tension, contact angle and the solids content of sputum in asthmatics with chronic cough and sputum production, consistent with the osmotic effect of mannitol causing water efflux in the airway lumen.

Activity of mannitol and hypertonic saline therapy on the oxidant and antioxidant system during the acute term after traumatic brain injury in the rats

In this study, our objective is to investigate the effects of mannitol and 7.5% hypertonic saline (HS) therapy on the levels of malondialdehyde (MDA), catalase and glutathione peroxidase (GSH-Px) in the early stages of experimental head traumas in rats. Rats included in the study were divided into four groups: Group I Control, Group II Trauma, Group III Mannitol, and Group IV 7.5% Hypertonic Saline. Rats in Group II were subject to head trauma only. Mannitol was injected intraperitoneally to rats in Group III after head trauma and 7.5% HS was injected intraperitoneally to rats in Group IV after head trauma. Rats were sacrificed 4 h after administration of mannitol or 7.5% HS, and the levels of MDA catalase and GSH-Px in brain tissues extracted from rats were determined. MDA levels in the trauma group were significantly increased compared with the control group (p<0.01), whereas there was a reduction in catalase and GSH-Px levels, although these differences were not significant. By contrast, in the mannitol group, MDA, catalase and GSH-Px levels were lower than the levels in the trauma group, and these reductions were statistically significant (p<0.05). The MDA, catalase and GSH-Px levels of the 7.5% HS group were lower than those of the trauma group; however, this reduction was not statistically significant. It was concluded that mannitol and 7.5% HS therapies that are used to reduce intracranial pressure and to increase the use of catalase, an antioxidant enzyme, and GSH-Px, are likely to reduce cellular damage by reducing the formation of MDA, the levels of which are known to be indicative of cellular level oxidant damage.

Intravenous hypertonic NaCl acts via cerebral sodium-sensitive and angiotensinergic mechanisms to improve cardiac function in haemorrhaged conscious sheep

Acute NaCl loading as resuscitation in haemorrhagic hypovolaemia is known to induce rapid cardiovascular recovery. Besides an osmotically induced increase in plasma volume the physiological mechanisms of action are unknown. We hypothesized that a CNS mechanism, elicited by increased periventricular [Na(+)] and mediated by angiotensin II type 1 receptors (AT(1)), is obligatory for the full effect of hypertonic NaCl. To test this we investigated the cardiovascular responses to haemorrhage and subsequent hypertonic NaCl infusion (7.5% NaCl, 4 ml (kg BW)(-1)) in six conscious sheep subjected to intracerebroventricular (i.c.v.) infusion of artificial cerebrospinal fluid (aCSF; control), mannitol solution (Man; 75 mmol l(-1) [Na(+)], total osmolality 295 mosmol kg(-1)) or losartan (Los; 1 mg ml(-1), AT(1) receptor antagonist) at three different occasions. Man normalized (144 +/- 6 mmol l(-1), mean +/- s.d.) the increase in i.c.v. [Na(+)] seen after aCSF (161 +/- 2 mmol l(-1)). Compared with control, both Man and Los significantly (P < 0.05) attenuated the improvement in mean arterial blood pressure (MAP), cardiac index and mesenteric blood flow (SMBF) in response to intravenous hypertonic NaCl: MAP, rapid response +45 mmHg versus +38 mmHg (Man) and +35 mmHg (Los); after 180 min, +32 mmHg versus +21 mmHg (Man) and +19 mmHg (Los); cardiac index after 180 min, +1.9 l min(-1) (m(2))(-1) versus +0.9 l min(-1) (m(2))(-1) (Man) and +0.9 l min(-1) (m(2))(-1) (Los); SMBF rapid response, +981 ml min(-1) versus +719 ml min(-1) (Man) and +744 ml min(-1) (Los); after 180 min, +602 ml min(-1) versus +372 ml min(-1) (Man) and +314 ml min(-1) (Los). The results suggest that increased periventricular [Na(+)] and cerebral AT(1) receptors contribute, together with plasma volume expansion, to improve systemic haemodynamics after treatment with hypertonic NaCl in haemorrhagic hypovolaemia.

Effects of mannitol in the prevention of lipid peroxidation during liver resection with hepatic vascular exclusion

STUDY OBJECTIVE

To examine the efficacy of mannitol in the prevention of lipid peroxidation during major liver resections performed during hepatic inflow occlusion.

DESIGN

Prospective, randomized, open-label study.

SETTING

Aretaieion Hospital, a university-affiliated hospital.

PATIENTS

30 ASA physical status II and III patients, less than 75 years of age, scheduled for elective liver resection.

INTERVENTIONS

All patients received combined general and epidural anesthesia. Laparotomy was performed through a bilateral subcostal incision, and hepatectomy was performed by inflow vascular exclusion (Pringle's maneuver). Before this maneuver, and if the patients were hemodynamically stable, they were randomized to receive either mannitol 20% 1.5 mL kg(-1) (group M) or normal saline 1.5 mL kg(-1) (group S) intravenously for 30 minutes.

MEASUREMENTS

Venous blood malondialdehyde (MDA) concentration, as an index of lipid peroxidation, was measured spectrophotometrically at selected time points.

MAIN RESULTS

Patients in both groups presented with raised MDA values (P < 0.05) for the period starting before the release of vascular occlusion until 6 days postoperatively. In patients receiving mannitol, lower MDA values were observed (P < 0.05) compared with group S at the end of operation.

CONCLUSION

Mannitol has an antioxidant activity, but we were unable to confirm a positive impact on the postoperative clinical course.

Low osmolarity transforms ventricular fibrillation from complex to highly organized, with a dominant high-frequency source

BACKGROUND

An osmotic challenge activates volume-regulated chloride currents (I(Cl,vol)), resulting in depolarization of the resting membrane potential and shortening of action potential duration (APD). I(Cl,vol) is activated in ischemia/reperfusion, but the effects of osmotic challenges and I(Cl,vol) on ventricular fibrillation (VF) are unknown.

OBJECTIVES

The purpose of this study was to investigate the influence of hypo-osmotic and hypotonic stress and I(Cl,vol) activation on VF dynamics.

METHODS

Guinea pig hearts were isolated, stained with di-4 ANEPPS to optically map action potentials (APs) from epicardium using a photodiode array, and perfused with iso-osmotic (low NaCl Ringer plus 45 mM mannitol) or hypo-osmotic (low NaCl Ringer) solution.

RESULTS

Hypo-osmotic solution shortened APDs (143 +/- 5 ms --> 115 +/- 10 ms) and increased APD gradients between right and left ventricles (21 +/- 7 ms --> 41 +/- 10 ms, n = 4). In VF induced by burst stimulation, switching to hypo-osmotic solution increased VF frequencies (15.3 +/- 1.2 Hz to 28.9 +/- 3.6 Hz, n = 11), transforming complex fast Fourier transformation spectra to a single dominant high frequency on the left but not the right ventricle. Perfusion with the I(Cl,vol) blocker indanyloxyacetic acid-94 (10 muM) reversed organized VF to complex VF with lower (13.5 +/- 3.7 Hz in left ventricle) frequencies (n = 8), indicating that I(Cl,vol) underlies the changes in VF dynamics. Consistent with this interpretation, the levels of ClC-3 channel protein were 27% greater on left than right ventricles (n = 10), and computer simulations showed that insertion of I(Cl,vol) transformed complex VF to a stable spiral.

CONCLUSION

Activation of I(Cl,vol) by decreasing osmolarity (45 mOsm) has a major impact on VF dynamics by transforming random multiple wavelets to a highly organized VF with a single dominant frequency.

Effects of acute hyperosmolality on blood-brain barrier function in ovine fetuses and lambs

We examined the effects of hyperosmolality on blood-brain barrier (BBB) permeability during development to test the vulnerability of the immature barrier to stress. The BBB response to hyperosmolality was quantified using the blood-to-brain transfer constant (Ki) with alpha-aminoisobutyric acid in fetuses at 60% and 90% gestation, premature, newborn, and older lambs. Ki plotted against osmolality increased as a function of increases in osmolality in all groups and brain regions. The relationship was described (P < 0.05) by a segmented regression model. At lower osmolalities, changes in Ki were minimal, but after a break point (threshold) was reached, the increase (P < 0.05) was linear. We examined the responses of Ki to hyperosmolality within each brain region by comparing the thresholds and slopes of the second regression segment. Lower thresholds and higher slopes imply greater vulnerability to hyperosmolality in the younger groups. Thresholds increased (P < 0.05) with development in the thalamus, superior colliculus, pons, and spinal cord, and slopes of the second regression segment decreased (P < 0.05) in the cerebellum, hippocampus, inferior colliculus, medulla, and spinal cord. BBB resistance to hyperosmolality increased (P < 0.05) with development in most brain regions. The pattern of the Ki plotted against osmolality was (P < 0.05) heterogenous among brain regions in fetuses and premature and newborn lambs, but not in older lambs. We conclude that 1) BBB permeability increased as a function of changes in osmolality, 2) the barrier becomes more resistant to hyperosmolality during development, and 3) the permeability response to hyperosmolality is heterogenous among brain regions in fetuses and premature and newborn lambs.

Role of pH in protection by low sodium against hypoxic injury in isolated perfused rat livers

BACKGROUND/AIMS

The purpose of the present study was to characterize the role of Na+, pH and cellular swelling in the pathogenesis of hypoxic injury to rat livers.

METHODS AND RESULTS

When livers were perfused with hypoxic Krebs-Henseleit bicarbonate buffer (KHB) containing 143 mM Na+, release of LDH began after 30 min and was maximal after 60 min. In livers perfused with choline-substituted low-Na+ KHB (25 mM Na+), LDH release began after 60 min and peaked after 120 min or longer. Supplementation of KHB with mannitol, a permeant sugar with antioxidant properties, suppressed LDH release, whereas sucrose, an impermeant disaccharide, did not afford protection. At the end of hypoxic perfusions with KHB and low-Na+ KHB, liver weight was not different, whereas mannitol but not sucrose increased liver weight after hypoxia. At pH 7.4, monensin, a Na+-H+ ionophore, reversed protection against hypoxia by low-Na+ KHB (10 mM Na+) but had no effect at pH 6.8. As measured directly by confocal microscopy of biscarboxyethylcarboxyfluorescein fluorescence, pH was lower during perfusion with low-Na+ KHB than KHB.

CONCLUSIONS

Cytoprotection by low Na+ was not mediated by prevention of Na+-dependent tissue swelling. Rather, promotion of intracellular acidification likely mediates cytoprotection in low-Na+ buffer.

Effect of free radical scavengers on myocardial function and Na+, K+-ATPase activity in stunned rabbit myocardium

OBJECTIVES

The role of reactive oxygen species (ROS) in the mechanism of myocardial stunning was investigated.

MATERIAL AND METHODS

Isolated Langendorff-perfused rabbit hearts were subjected to 15 min normothermic ischemia followed by 10 min reperfusion with Krebs-Henseleit solution+/-mannitol or histidine.

RESULTS

In hearts reperfused without free radical scavenger the left ventricular developed pressure as well as its maximal positive and negative first derivatives (+dP/dt, -dP/dt) was significantly depressed, whereas end diastolic pressure (LVEDP) increased when compared to preischemic values. Treatment with mannitol had little protective effects, whereas singlet oxygen scavenger histidine significantly improved the recovery of LVEDP and -dP/dt. Sarcolemmal Na+, K+-ATPase activity (control, 400+/-41 nmol Pi.min-1.mg-1) was depressed in untreated stunned hearts (260+/-27 nmol Pi.min-1.mg-1), but was almost completely recovered in hearts pretreated with histidine (364+/-27 nmol Pi.min-1.mg-1). The inhibition of Na+, K+-ATPase was only slightly prevented by mannitol (302+/-29 nmol Pi.min-1.mg-1l).

CONCLUSIONS

The results suggest that ROS-induced inhibition of Na+, K+-ATPase activity is involved in the mechanism of postischemic contractile dysfunction and support the view that singlet oxygen may be one of the major causes of oxidative injury during ischemia and reperfusion.

Isosorbide delays gentamicin-induced vestibular sensory cell death

The efficacy of isosorbide for protection from vestibular sensory cell damage was investigated. The effects of isosorbide on gentamicin-induced production of nitric oxide (NO) and reactive oxygen species (ROS) were studied by means of the fluorescence indicators 4,5-diaminofluorescein diacetate and dihydrotetramethylrosamine. The effect on gentamicin-induced vestibular sensory cell damage was examined by using an in vitro LIVE/DEAD system. Isosorbide inhibited the production of both NO and ROS. Isosorbide limited the vestibular sensory cell damage caused by gentamicin. It is, therefore, suggested that isosorbide may help to treat inner ear disorders.

Mannitol but not dantrolene prevents myocardial dysfunction following intra-cranial hypertension in rats

Cardiac complications stemming from intra-cranial hypertension may result from impaired intra-cellular Ca(2+) homeostasis. The aim of this study was to examine the effects of dantrolene, a blocker of sarcoplasmic reticulum (SR) Ca(2+) release, on myocardial dysfunction associated with intra-cranial hypertension in rats. Dantrolene (10 mg) with and without 15% mannitol was administered to halothane-anesthetized rats prior to induction of intra-cranial hypertension by subdural balloon inflation. Its effects were compared to 3% and 15% mannitol and 5% Pentaspan. Dantrolene with mannitol or 15% mannitol alone prevented the transient intra-cranial hypertension-induced hyperdynamic response and ensuing circulatory collapse that was found in animals pre-treated with 3% mannitol solution or pentaspan. Moreover, hemodynamic function was preserved irrespective of TnI cleavage. However, only animals treated with high dose 15% mannitol exhibited lower lipid peroxidation content in the heart. In contrast, pre-treatment with dantrolene alone did not prevent the cardiac complications associated with intra-cranial hypertension. In conclusion, 15% mannitol attenuated the cardiopulmonary complications associated with intra-cranial hypertension. Dantrolene without mannitol was without effect. Since mannitol exhibits free radical scavenging properties, protection could be the result of a decrease in oxidative stress after intra-cranial hypertension.

Water transport by Na+-coupled cotransporters of glucose (SGLT1) and of iodide (NIS). The dependence of substrate size studied at high resolution

The relation between substrate and water transport was studied in Na+-coupled cotransporters of glucose (SGLT1) and of iodide (NIS) expressed in Xenopus oocytes. The water transport was monitored from changes in oocyte volume at a resolution of 20 pl, more than one order of magnitude better than previous investigations. The rate of cotransport was monitored as the clamp current obtained from two-electrode voltage clamp. The high resolution data demonstrated a fixed ratio between the turn-over of the cotransporter and the rate of water transport. This applied to experiments in which the rate of cotransport was changed by isosmotic application of substrate, by rapid changes in clamp voltage, or by poisoning. Transport of larger substrates gave rise to less water transport. For the rabbit SGLT1, 378+/-20 (n=18 oocytes) water molecules were cotransported along with the 2 Na+ ions and the glucose-analogue alpha-MDG (MW 194); using the larger sugar arbutin (MW 272) this number was reduced by a factor of at least 0.86+/-0.03 (15). For the human SGLT1 the respective numbers were 234+/-12 (18) and 0.85+/-0.8 (7). For NIS, 253+/-16 (12) water molecules were cotransported for each 2 Na+ and 1 thiocyanate (SCN-, MW 58), with I- as anion (MW 127) only 162+/-11 (19) water molecules were cotransported. The effect of substrate size suggests a molecular mechanism for water cotransport and is opposite to what would be expected from unstirred layer effects. Data were analysed by a model which combined cotransport and osmosis at the membrane with diffusion in the cytoplasm. The combination of high resolution measurements and precise modelling showed that water transport across the membrane can be explained by cotransport of water in the membrane proteins and that intracellular unstirred layers effects are minute.

Hyperosmotic mannitol induces Src kinase-dependent phosphorylation of beta-catenin in cerebral endothelial cells

Mannitol, which is a cell-impermeable and nontoxic polyalcohol, has been shown to be a useful tool for reversible opening of the blood-brain barrier (BBB). Despite successful clinical trials, the molecular mechanism of the mannitol-induced changes in cerebral endothelial cells (CECs) are poorly understood. For our experiments, we used CECs in culture, which were treated with different, clinically relevant concentrations of mannitol. We found that mannitol induced a rapid, concentration-dependent, and reversible tyrosine phosphorylation of a broad range of proteins between 50 and 190 kDa. One of the targets of tyrosine phosphorylation turned out to be the adherens junction protein beta-catenin. Phosphorylation of beta-catenin on tyrosine residues caused its subcellular redistribution and its dissociation from cadherin and alpha-catenin as shown by coimmunoprecipitation studies. All these effects could be inhibited by the Src kinase inhibitor PP-1 but not by the Erk inhibitor U0126, the Rho kinase inhibitor Y27632, or the calcium channel blocker verapamil. Because beta-catenin is a key component of the junctional complex, its Src-mediated phpsphorylation may play an important role in the mannitol induced reversible opening of the BBB.

Hyperosmolar therapy in the treatment of severe head injury in children: mannitol and hypertonic saline

Traumatic brain injury is the result of a primary, acute injury and is complicated by the development of secondary injury due to hypotension and hypoxia. Cerebral edema due to brain injury compromises the delivery of essential nutrients and alters normal intracranial pressure. The Monroe-Kellie Doctrine defines the principles of intracranial pressure homeostasis. Treatment for intracranial hypertension is aimed at reducing the volume of 1 of the 3 intracranial compartments, brain tissue, blood, and cerebrospinal fluid. Hyperosmolar therapy is one treatment intervention in the care of patients with severe head injury resulting in cerebral edema and intracranial hypertension. The effect of hyperosmolar solutions on brain tissue was first studied nearly 90 years ago. Since that time, mannitol has become the most widely used hyperosmolar solution to treat elevated intracranial pressure. Increasingly, hypertonic saline solutions are being used as an adjunct to mannitol in basic science research and clinical studies. Hyperosmolar solutions are effective in reducing elevated intracranial pressure through 2 distinct mechanisms: plasma expansion with a resultant decrease in blood hematocrit, reduced blood viscosity, and decreased cerebral blood volume; and the creation of an osmotic gradient that draws cerebral edema fluid from brain tissue into the circulation. The pediatric section of the Society of Critical Care Medicine and the World Federation of Pediatric Intensive and Critical Care Societies adapted previously published guidelines for the treatment of adult brain injury into guidelines for the treatment of children with traumatic brain injury. These guidelines offer recommendations for the management of children with severe head injury, including the use of mannitol and hypertonic saline to treat intracranial hypertension. Acute and critical care pediatric advanced practice nurses caring for children with severe head injury should be familiar with management guidelines and the use of hyperosmolar solutions. The purpose of this article is to assist the advanced practice nurse in understanding the role of hyperosmolar therapy in the treatment of pediatric traumatic brain injury and review current guidelines for the use of mannitol and hypertonic saline.

Brain dysfunction in uremia: a question of cortical hyperexcitability?

OBJECTIVE

To investigate whether patients with end-stage renal disease (ESRD) in different stages of the disease and undergoing different treatments display alterations in cortical excitability.

METHOD

A total of 36 patients with ESRD were evaluated at different stages of the disease and under different treatment by using standard transcranial magnetic stimulation (TMS) parameters. Moreover patients under haemodialysis underwent a double-blind crossover study (mannitol vs placebo) in order to better elucidate the pathophysiology of the acute effects of haemodialysis on cortical excitability.

RESULTS

Patients with ESRD in conservative therapy showed a significant reduction of short-interval intra-cortical inhibition (SICI). This alteration could be reversed by haemodialysis, peritoneal dialysis and by renal transplantation. After haemodialysis there was a significant increase of intra-cortical facilitation (ICF) inversely correlated with the drop in plasma osmolarity induced by the dialytic procedure. Mannitol infusion prevented the drop in plasma osmolarity and the haemodialysis-related changes in ICF.

CONCLUSIONS

ESRD patients showed alterations in cortical excitability that can be reversed by replacement therapies. We propose that the drop in plasma osmolarity is a key to the mechanism underlying post-haemodialysis cortical hyperexcitability.

SIGNIFICANCE

The results of this study give further insight to the pathophysiology of brain abnormalities in patients with chronic renal failure.

Systemic mannitol-induced hyperosmolality amplifies rAAV2-mediated striatal transduction to a greater extent than local co-infusion

Recombinant viral vectors derived from adeno-associated virus serotype 2 (rAAV2) have been investigated as highly effective vehicles for gene transfer to the central nervous system (CNS). Transduction with rAAV2 vectors results in long-term transgene expression in CNS neurons. Optimal injection parameters leading to efficient targeting and spread of the transgene to large neuroanatomical regions are important in molecular gene therapy studies of the CNS. In the present study, we reexamined the effects of both local and systemic administration of mannitol-induced hyperosmolality on facilitation of transgene expression and vector distribution in the CNS. Systemic intraperitoneal administration of mannitol prior to vector administration improved gene transfer to striatal neurons, increasing the total number of transduced cells by 400% and vector distribution by 200%. On the other hand, local coadministration of mannitol in the striatum increased the number of transduced striatal neurons by 25% and had little effect on transduction volume. In conclusion, we have demonstrated that systemic coadministration of mannitol significantly enhances transgene spread of rAAV2 viral delivery in the brain to a much greater degree than local coadministration.

Heat shock treatment protects osmotic stress-induced dysfunction of the blood-brain barrier through preservation of tight junction proteins

The blood-brain barrier (BBB) is a specialized structure in the central nervous system (CNS), which participates in maintenance of a state of cerebrospinal fluid homeostasis. The endothelial cells of the cerebral capillaries and the tight junctions between them form the basis of the BBB. Research has shown that destruction of the BBB is associated with diseases of the CNS. However, there is little research on how the BBB might be protected. In this study, we used a high osmotic solution (1.6 M D-mannitol) to open the BBB of rats and Evans blue dye as a macromolecular marker. The effect of heat shock treatment was evaluated. The results show that increased synthesis of heat shock protein 72 (Hsp72) was induced in the heated group only. BBB permeability was significantly less in the heat shock-treated group after hyperosmotic shock. The major tight junction proteins, occludin and zonula occludens (ZO)-1, were significantly decreased after D-mannitol treatment in the nonheated group, whereas they were preserved in the heated group. The coimmunoprecipitation studies demonstrated that Hsp72 could be detected in the precipitates of brain extract interacting with anti-ZO-1 antibodies as well as those interacting with anti-occludin antibodies in the heated group. We conclude that the integrity of tight junctions could be maintained by previous heat shock treatment, which might be associated with the increased production of Hsp72.

Characterization of rPEPT2-Mediated Gly-Sar Transport Parameters in the Rat Kidney Proximal Tubule Cell Line SKPT-0193 cl.2 Cultured in Basic Growth Media

The rat proximal kidney tubule cell line SKPT-0193 cl.2 (SKPT) expresses the di-/tripeptide transporter PEPT2 (rPEPT2) and has been used to study PEPT2-mediated transport. Traditionally, SKPT cells have been cultured in growth media supplemented with epidermal growth factor (EGF), apotransferrin, dexamethasone, and insulin. It was recently demonstrated that omission of EGF from the culture media caused a drastic increase in the expression of rPEPT2. The hypothesis was therefore that the SKPT cell line might be able to differentiate and express rPEPT2 in the absence of the four agonists traditionally added. The aim of the study was thus to characterize Gly-Sar transport parameters in SKPT cells cultured in basic growth media (conventional media without added agonists). Morphology was studied using confocal laser scanning microscopy (CLSM) and immunohistochemistry. Monolayer integrity was evaluated using transepithelial electrical resistance (TEER) measurements and [(3)H]-mannitol permeabilities. Di-/tripeptide transporter activity was studied using [(14)C]-glycylsarcosine ([(14)C]-Gly-Sar). SKPT cells grown in basic media for 4 days formed confluent monolayers with a TEER of 5.03 +/- 0.33 kOmega.cm(2) (n = 5). Apical Gly-Sar uptake peaked after 3-6 days in culture. Uptake at day 4 was 5.89 +/- 0.30 pmol.cm(-2).min(-1) (n = 3). Di-/tripeptide uptake displayed an optimum at approximately pH 6. Affinity values for cephalexin, kyotorphin, and delta-aminolevulinic acid were comparable to those obtained in other PEPT2-expressing model systems. It can be concluded that SKPT cells grown in the absence of the agonists traditionally added to the culture media retain all necessary properties for PEPT2-mediated peptide uptake studies. Furthermore, the absence of the agonists might facilitate studies of hormonal regulation of PEPT2 expression and transport activity.

Involvement of Adenosine Triphosphate-Sensitive Potassium Channels in the Response of Membrane Potential to Hyperosmolality in Cultured Human Aorta Endothelial Cells

The membrane potential of endothelial cells is an important determinant of endothelial functions, including regulation of vascular tone. We investigated whether adenosine triphosphate-sensitive potassium (K(ATP)) channels were involved in the response of membrane potential to hyperosmolality in cultured human aorta endothelial cells. The voltage-sensitive fluorescent dye, bis-(1,3-diethylthiobarbiturate)trimethine oxonol, was used to assess relative changes in membrane potential semiquantitatively. To investigate the effect of mannitol-, sucrose-, and NaCl-induced hyperosmolality on membrane potential, cells were continuously perfused with Earle's balanced salt solution (285 mOsm/kg H(2)O) containing 200 nM bis-(1,3-diethylthiobarbiturate)trimethine oxonol and exposed to 315 and 345 mOsm/kg H(2)O hyperosmotic medium sequentially in the presence and absence of 1 muM glibenclamide, a well-known K(ATP) channel blocker. Hyperosmotic mannitol significantly induced hyperpolarization of the endothelial cells, which was prevented by 1 microM glibenclamide (n = 6). Estimated changes of membrane potential at 315 and 345 mOsm/kg H(2)O were 13 +/- 8 and 21 +/- 8 mV, respectively. Hypertonic sucrose induced similar changes. However, although hypertonic saline also significantly induced hyperpolarization of the endothelial cells (n = 6), the hyperpolarization was not prevented by 1 muM glibenclamide. In conclusion, K(ATP) channels may participate in hyperosmotic mannitol- and sucrose-induced hyperpolarization, but not in hypertonic saline-induced hyperpolarization in cultured human aorta endothelial cells.

Effects of vasoactive intestinal polypeptide microinjected into the nucleus tractus solitarius on jejunal electrolytes absorption in rats

It has been shown that vasoactive intestinal polypeptide (VIP) injected into the nucleus tractus solitarius inhibits alanine absorption across the jejunum. The aim of the present study was to investigate the effects of VIP injection into the nucleus tractus solitarius on jejunal absorption of electrolytes in the rat. Fifty-three Wistar rats were submitted to midline laparotomy to expose and isolate 20 cm of jejunal loop and to perform a subdiaphragmatic troncular vagotomy. Saline or VIP (10 pg 100 nl(-1)) was injected into the rostral nucleus tractus solitarius using a stereotaxic instrument. Tyrode solution, pH 8, containing twice glucose, sodium and potassium concentration was infused (0.5 ml min(-1)) into the jejunal loop. Samples were taken at 10-min intervals during the 40-min-experiment. Injection of VIP into the nucleus tractus solitarius increased jejunal potassium absorption. Moreover, VIP associated with vagotomy resulted in inhibition of jejunal potassium absorption by VIP alone at 40 min after perfusion (5.99 +/- 0.74 vs. 9.83 +/- 0.57 microM). There was no change in jejunal sodium absorption in any of the experimental groups. VIP had a modulatory action on jejunal potassium absorption when injected into the nucleus tractus solitarius.

Effect of hyperosmolarity on beta2-adrenergic stimulation in human atrium

The purpose of the present study was to determine whether extracellular osmotic pressure modulates beta2-adrenergic stimulation of the contraction force and L-type Ca2+ current in human atrial myocytes. Experiments were performed on human atrial trabeculae and myocytes isolated from the right atrium. We have studied the effect of salbutamol (SAL), a beta2-adrenoceptor agonist, on peak tension (P), time to half peak tension (tc), time to half relaxation (tr), resting tension (contracture) (C) and L-type calcium current (ICaL) under isosmotic (345 mOsm) and hyperosmotic (525 mOsm in experiments for P, and 405 mOsm for ICaL) conditions. Salbutamol (10(-8)/10(-5) M) added to the control solution increased P, with a half-stimulation constant EC50=(2.7+/-0.6)x10(-8) M (p<0.05) and the maximal stimulation of contraction force Pmax=180.6+/-45.8% (n=10). The time to half peak and time to half relaxation were reduced by salbutamol to 89.1+/-2.7% and 78.8+/-4.1% (n=8), respectively. Mannitol (180 mM) added to the Tyrode solution decreased Pmax to 34+/-5.5%; tc, tr and C were increased to 126.3+/-7.2%, 158.3+/-22.6% (n=4) and 0.54+/-0.22 (n=5) of the control level, respectively. Under these hyperosmotic conditions the same concentrations of SAL increased P with a half-stimulation constant EC50=(6.4+/-2.6)x10(-7) M and Pmax=57.2+/-12.6% (n=4). The tc and tr were reduced by 23.2+/-5.9% and 53.1+/-19.4% (n=4), respectively (as compared to mannitol). There was no significant effect of salbutamol on the resting tension induced by mannitol. Under isosmotic conditions salbutamol (10(-9)/10(-6) M) increased ICaL with an EC50 value of (2.9+/-0.9)x10(-9) M and Emax 182.3+/-19.8% (n=4). In hyperosmotic solutions the EC50 and Emax for ICaL were (1.2+/-0.5)x10(-8) M and 217.2+/-70.5%, respectively (n=5). These results indicated that hyperosmolarity reduced the effect of beta2-adrenergic stimulation on human atrial cells.

Effect of mannitol on regional cerebral blood flow in patients with intracerebral hemorrhage

AIM

To evaluate the regional cerebral blood flow (rCBF) changes following IV mannitol bolus in patients with intracerebral hemorrhage (ICH).

METHODS

In a hospital based randomized placebo controlled study, 21 CT proven ICH patients with Glasgow coma scale (GCS) score of 5 or more were subjected to clinical evaluation including GCS and Canadian Neurological stroke (CNS) scale. Cranial SPECT study was undertaken before and 60 min after 20% mannitol 100 ml IV in 20 min or sham infusion. The SPECT images were semi-quantitatively analyzed and asymmetry index of basal ganglia, frontal, parietal and occipital regions were calculated.

RESULTS

There were 12 patients in mannitol and nine in control group who were evenly matched for age, mean arterial blood pressure, GCS score and size of hematoma. Only one patient died in mannitol group. Following mannitol, GCS score improved in six, worsened in two and remained unaltered in four patients. In the control group, GCS improved in seven, worsened in none and was unchanged in two patients. SPECT studies revealed reduction in asymmetry index in basal ganglia in four, frontal region in six, parietal in four and occipital region in five patients in mannitol group. In control group, asymmetry index was reduced in basal ganglia in one, frontal and parietal region in three each and occipital region in five patients. These differences between control and study group were not significant.

CONCLUSION

Mannitol does not seem to significantly change the regional cerebral blood flow (rCBF) in ICH patients as evaluated by SPECT study.

Self-complementary adeno-associated virus serotype 2 vector: global distribution and broad dispersion of AAV-mediated transgene expression in mouse brain

The blood-brain barrier is the main obstacle to efficient delivery of therapeutic reagents, including viral vectors, into the central nervous system (CNS) for treating global CNS diseases. In this study, the effects of mannitol infusions on global brain gene expression of a novel AAV vector were examined after intravenous (i.v.) or intracisternal injection. Initially, a self-complementary adeno-associated virus serotype 2 vector (scAAV) was compared to traditional single-stranded AAV2 vector for reporter gene expression in the brain of adult mice with or without pretreatment of an i.v. mannitol infusion. One to two months postinjection, analysis of vector-transduced green fluorescent protein (GFP) expression in the brain revealed that vector delivery to the CNS via i.v. injection required pretreatment with mannitol. This expression was observed only when scAAV vectors were used. Using these conditions, transgene expression was observed in various neurons and glial cells throughout the brain. The peripherally administered scAAV vectors also transduced the cells in multiple somatic tissues with efficient expression in liver (20-30% of hepatocytes), but was less efficient in other somatic tissues. Intracisternal injection of scAAV vector produced a broad and intense transgene expression in both neurons and glial cells in the CNS of injected mice ranging from the olfactory area to the brain stem and spinal cord. More than 50% of the Purkinje cells in the cerebellum expressed GFP. Intravenous infusion of mannitol before intracisternal injection of the scAAV vector enhanced the dispersion of the vector in the CNS. Further optimization of these steps combining peripheral and intracisternal scAAV gene delivery should facilitate the development of treatments for global CNS diseases, especially diseases involving both the somatic system and the CNS, such as lysosomal storage disorders.

Hormone release is tied to changes in cell size in the osmoreceptive prolactin cell of a euryhaline teleost fish, the tilapia, Oreochromis mossambicus

Prolactin (PRL) cells from a teleost fish, the tilapia, Oreochromis mossambicus, facilitate the direct study of osmoreception. The release of two prolactins, PRL(188) and PRL(177), which act in freshwater osmoregulation in teleost fish, rises in vitro within 5 min after extracellular osmolality falls. An increase in cell size accompanied this rise. Cell size and PRL release also increased, albeit more slowly, following the partial replacement of medium NaCl (55 mOsmolal) with an equivalent concentration of urea, a membrane-permeant molecule. Similar replacement using mannitol, which is membrane-impermeant, elicits no response. These findings suggest that osmoreception is linked to changes in cell volume rather than to extracellular osmolality per se.

Application of red laser video-rate scanning confocal microscopy toin vivoassessment of tubular function in the rat: selective action of diuretics on tubular diameter

This study examined the use of a red laser illuminated, video-rate scanning confocal reflection microscopy (VRSCM) system, with improved structural and functional imaging at high temporal resolution, to visualize physiological changes in the kidney in response to pharmacological stimuli. We applied VRSCM to superficial nephrons in vivo and measured temporal changes in the diameter of proximal and/or distal tubular segments in response to the administration of three major classes of diuretics with known selective actions at specific nephron sites. Mannitol caused measurable increases in both proximal and distal tubular diameter, whereas frusemide and hydrochlorothiazide caused dilation of the distal tubules only. The findings indicate that VRSCM is capable of detecting and quantifying predicted dynamic changes in renal tubular diameter.

Gene regulation of renal-osmotic stress-induced Na-CL organic solute cotransporter

BACKGROUND

Na- and Cl-dependent organic solute cotransporters participate in transporting neurotransmitters in the brain and organic osmolytes in the kidney.

METHODS

We examined the intranephron localization and regulation of the renal osmotic-stress-induced Na-Cl organic solute cotransporter (ROSIT) mRNA expression using microdissected nephron segments from control and dehydrated rats and RT-PCR. To further know the mechanisms of gene regulation of ROSIT, microdissected proximal straight tubules (PST) were incubated in isotonic (290 mosm/kg H2O) or hyperosmotic (490- 1,090 mosm/kg H2O) solution.

RESULTS

ROSIT mRNA was expressed predominantly in PST and to a lesser extent in cortical thick ascending limbs and cortical collecting ducts in control rats, and dehydration caused an increase in the expression in whole nephron segments. ROSIT mRNA in PST was decreased with time by incubation in isotonic solution. Incubation of PST in hypertonic solution by adding NaCl increased mRNA expression as early as 15 min (1.5- and 3-fold at 15 and 30 min, respectively). This stimulating effect of NaCl was largest at 890 mosm/kg H2O. Hypertonicity by mannitol or myoinositol also increased ROSIT mRNA expression. In contrast, hyperosmolality by urea reduced ROSIT mRNA expression. GAPDH mRNA expression, an internal standard, did not change by incubation in NaCl or mannitol solution.

CONCLUSION

In summary, ROSIT mRNA expression was most abundant in PST in control and it was stimulated in whole nephron segments by dehydration. ROSIT mRNA expression in PST was stimulated by hypertonicity but not by urea. These data suggest that ROSIT may participate in the transport of amino acid under control conditions and organic osmolytes in dehydration.

Time Course of Dehydrating Effects of Isosorbide on Experimentally Induced Endolymphatic Hydrops in Guinea Pigs

Osmotic diuretics are therapeutic agents used to reduce endolymphatic hydrops. However, glycerol-induced change in endolymph volume is followed by a rebound phenomenon. In this study, we investigated the rebound phenomenon occurring with isosorbide, an osmotic diuretic used as a therapeutic agent for Ménière's disease in Japan. Forty guinea pigs underwent surgical obliteration of the endolymphatic sac. Thirty received isosorbide orally 1 month after surgery. These animals were sacrificed 3, 6, or 12 h after isosorbide intake. The remaining 10 animals served as controls. Quantitative assessment of changes in the endolymphatic space was performed light-microscopically. Isosorbide reduced cochlear endolymph volume, with a peak reduction 6 h after intake. Thereafter, no prominent rebound phenomenon was noted. Clinically, since isosorbide is orally administered every 8 h, rebound phenomenon need not be considered in the treatment with isosorbide.

[Effects of metabolic substrates and mannitol on efficiency of cardioplegic protection in isolated rat heart]

The aim of this work was to study rationality of addition of aspartic acid, phosphocreatine, mannitol and tris(bydroxymethyl) aminomethane (trisamine) to a sanguineous cardioplegic solution. Isolated perfused rat hearts were subjected to 40-min normothermic total ischemia and 30-min reperfusion. Cardioplegic solutions were infused for 5 min prior to ischemia. A modified Ringer solution with 25 mM KCI was used as control. Osmolarity and pH of cardioplegic solutions were 340+/-5 mOms and 7.6+/-0.1 at 22 degreesC, respectively. Efficiency of myocardial protection was evaluated by recovery of contractile and pump function during reperfusion. The optimal solution contained aspartic acid (21.5 mM), mannitol (20.0 mM) and trisamine (5 mM). By the end of reperfusion the heart protected by this solution showed almost complete recovery of coronary flow (98+/-3% of the initial value vs. 77+/-3% in the control), and 2.6-fold higher recovery of stroke volume compared to the control. As a result, recovery of external cardiac work index, calculated as cardiac output-mean perfusion pressure, was 64+/-1% of the initial value vs. 24+/-5% in the control. Increase in buffer capacity of this cardioplegic solution by trisamine (up to 20.0 mM) as well as addition of phosphocreatine (10.0 mM) did not result in further augmentation of cardiac function recovery. The results suggest promising perspectives for development of medicinal form of this solution.

Glucose-induced changes in the phenotype of human peritoneal mesothelial cells: effect of L-2-oxothiazolidine carboxylic acid

BACKGROUND

During peritoneal dialysis, mesothelial cells are chronically exposed to high concentrations of glucose. Therefore, the cytotoxic effect of glucose may alter the function and reactivity of these cells.

METHODS

For 4 weeks, human peritoneal mesothelial cells were cultured in vitroin medium supplemented with 45 mM glucose or 45 mM mannitol or with 45 mM glucose and 1 mM L-2-oxothiazolidine-4-carboxylic acid (OTZ), the latter being a precursor for glutathione synthesis. Peroxidation of the mesothelial cell lipids, synthetic activity and reaction of these cells to peritoneal dialysis fluids were studied.

RESULTS

In contrast to mannitol, glucose enhanced the peroxidation of the cellular lipids (+65%, p < 0.01) an effect that was prevented by OTZ. Synthesis of hyaluronan and vascular endothelial growth factor was reduced in mesothelial cells treated with glucose by 36% (p < 0.01) and 44% (p < 0.05), respectively; both glucose effects were reversed when cells were incubated with glucose plus OTZ. Monocyte chemoattractant protein-1 synthesis by cells exposed to glucose was increased by 31% (p < 001), and again that effect was prevented by OTZ. Glucose and mannitol stimulated synthesis of fibronectin (+32%, p < 0.05). Mesothelial cells chronically exposed to glucose became activated after subsequent exposure to the dialysis fluid, as reflected by the increased release of interleukin (IL)-6, in contrast to control mesothelial cells, in which IL-6 synthesis was suppressed.

CONCLUSIONS

Chronic exposure of mesothelial cells to glucose changes their synthetic activity and their reaction after exposure to dialysis fluids. Some of these effects are prevented by OTZ, which suggests that glucose-induced free radicals are responsible for a change in mesothelial cell phenotype under the conditions of peritoneal dialysis.

Effect of mannitol in experimental spinal cord injury: an ultrastructural and electrophysiological study

BACKGROUND

Although many experimental and clinical studies were performed on the pathophysiology and treatment of spinal cord injury (SCI), the electrophysiological and ultrastructural changes of the spinal cord were not precisely evaluated.

AIMS

To investigate the effect of mannitol on Somatosensory Evoked Potentials (SSEP), postoperative neurological recovery and ultrastructural findings after an experimental SCI.

SETTING

The experimental microsurgery laboratory of a university hospital.

DESIGN

A prospective, randomized animal study.

MATERIAL AND METHODS

Sprague-Dawley rats were used and divided into three groups (Groups I-III) for this study. Those in Group I were control animals who underwent laminectomy only, and non-traumatized spinal cord samples were obtained 2 weeks later. SCI was produced in Groups II and III using clip compression technique, and cord samples were obtained 2 weeks later. The rats in Group II received 2 g/kg of 20% mannitol intraperitoneally, immediately and three hours after trauma was induced; and those in Group III received the same amount of 0,9% NaCl in the same manner. Preoperative and postoperative SSEP records at the end of 2 weeks were obtained. Electron microscopy examination of the cord samples was done at 2 weeks postoperatively.

STATISTICAL ANALYSIS USED

Fischer's Exact Test.

RESULTS

SSEP records, ultrastructural findings and clinical recovery showed that minor neural damage and significant recovery occurred in Group II.

CONCLUSION

This study demonstrates that the administration of 2 g/kg of 20% mannitol produces significant improvement in the neural structures and protects the spinal cord following injury.

An evaluation of the effects of three laryngeal lubricants on phonation threshold pressure (PTP)

Clinicians frequently offer advice to performers and voice-disordered patients aimed ostensibly to manipulate the water content and/or viscosity of the mucus blanket covering the vocal folds. To evaluate the relative effects of three potential laryngeal lubricants on phonatory function (ie, water, Mannitol--an osmotic agent, and Entertainer's Secret Throat Relief (Kli Corp., Carmel, IN)--a glycerin-based product), phonation threshold pressure (PTP) was measured in 18 healthy, vocally normal female participants twice before (baseline) and then four times after 2 ml of each substance were nebulized. PTP is the minimum subglottal pressure required to initiate vocal fold oscillation, and the lowering of PTP is assumed to correspond to physiologically more efficient phonation and reduced phonatory effort. Over a 3-week period, participants were tested on three separate occasions (at 1-week intervals). On each occasion, a different nebulized treatment was administered. PTP for both comfortable and high fundamental frequency productions was measured using an oral pressure-flow system (Perci-Sars, MicroTronics Corp., Chapel Hill, NC). Analysis of the results revealed that Mannitol, an agent that encourages osmotic water flux to the luminal airway surface, lowered PTP immediately after its administration (ie, p = 0.071, for high-pitched productions only). However, the duration of its PTP lowering effect was less than 20 minutes. The other two substances did not demonstrate any significant postadministration effect on PTP.

Release of inflammatory mediators from eosinophils following a hyperosmolar stimulus

Airway dehydration and subsequent hyperosmolarity of periciliary fluid are considered critical events in exercise-induced bronchoconstriction (EIB). It has been shown that an in vitro hyperosmolar stimulation of basophils and mast cells with mannitol can induce the release of histamine and leukotrienes. The aim of this study was to establish if a hyperosmolar challenge could trigger activation of eosinophils to release chemokines and lipid mediators. Peripheral blood eosinophils were isolated from seven asthmatic and six non-asthmatic subjects. Hyperosmolar stimulation of eosinophils with mannitol (0.7 M), resulted in a significant increase in LTC4 levels compared to baseline in both asthmatic (15.2+/-4.6 vs. 70.1+/-9.5; P = 0.0002) and control subjects (14.3+/-4.0 vs. 55.6+/-5.6; P = 0.0001). ECP levels did not increase significantly above baseline following mannitol stimulation in either group. This study shows that eosinophils can be activated by a hyperosmolar stimulus. Therefore it seems reasonable to suggest that eosinophils could contribute to EIB.

Comparative study of the use of diltiazem as an antispasmodic drug in coronary angiography via the transradial approach

OBJECTIVE

To evaluate the impact of the use, prior to the procedure, of injectable diltiazem to prevent complications.

METHODS

Between September 2000 and July 2001, 50 patients underwent transradial coronary angiography and were randomized to receive placebo (GI) or diltiazem (GII) through a catheter inserted into the radial artery. All patients received isosorbide mononitrate. Ultrasound analyses of the radial artery were performed before examination, 30 minutes afterwards, and 7 days afterwards to evaluate the flow, the diameter, and the artery output.

RESULTS

The radial artery diameter of GI was 2.4d +/- 0.5 mm before the procedure and 2.3 +/- 0.5 mm after 30 minutes (NS), whereas in GII the diameter was 2.2 +/- 0.3 mm before the examination and +/- 2.5 0.4 mm 30 minutes after it (P<0.001). Radial artery output in group 1 was 7.3 +/- 5.l2 mL/min before the examination and 6.1 +/- 3.5 mL/min 30 minutes after the examination (NS), and GII had an increase of 5.9 +/- 2.5 mL/min before examination to 9.05 +/- 7.78 mL/min after the examination (P=0.04). Complications (spasm, occlusion, and partial obstruction) occurred in 4 patients (17.4%) in GI and did not occur in GII (P=0.04).

CONCLUSION

The study suggests a decrease in vascular complications through the transradial access for coronary angiography with the use of diltiazem as an antispasmodic drug, resulting in the significant increase in the diameter of the radial artery and radial artery output.