Disorders of water imbalance

Intravenous Infusion of Sterile Water for the Treatment of Hypernatraemia

Little research has been carried out into the infusion of intravenous sterile water for the treatment of hypernatraemia, and it remains a contentious issue. We conducted a review of the literature and extract results following an extensive search of Medline 1946, Embase 1974, ProQuest, evidence-based practice resources, national and international guideline sites and the publications of various professional bodies. The review is presented on the infusion of sterile water (hypotonic fluid) to lower serum sodium level in those circumstances when enteral supplementation of water is not possible, such as in postoperative patients or when other isotonic fluids (such as 5% dextrose in water infusion) are less than ideal—for example, hyperglycaemic patients on an insulin infusion. Absence of guidelines has limited the use of sterile water, even as an off-label drug when it can be administered relatively safely via a central line.

Continuous veno-venous hemofiltration in the treatment of severely burned patients with acute hypernatremia: A retrospective study of 13 cases

OBJECTIVES

This study aimed to evaluate the clinical effects of continuous veno-venous hemofiltration in the treatment of severely burned patients with acute hypernatremia.

METHODS

A total of 13 severely burned patients with acute hypernatremia admitted to Xijing Hospital were included in this study. All patients received continuous veno-venous hemofiltration treatment in addition to conventional treatment. The original sodium level in the replacement fluid was set to be lower than the serum sodium level by 8 mmol/L and subsequently undergoes a reduction rate of 2.16 ± 0.18 mmol/L every 4 h. Patients' clinical features, serum laboratory tests, hemodynamic variables, changes in sodium levels in serum, and replacement fluid during continuous veno-venous hemofiltration treatment were monitored.

RESULTS

Patients had an average total burn surface area of 66.69% ± 20.28%. Two patients died of systematic Pseudomonas aeruginosa infections, and 11 patients survived. After continuous veno-venous hemofiltration treatment, patients showed a significant reduction in the serum sodium level (168.91 ± 4.88 mmol/L vs 144.62 ± 2.98 mmol/L, p < 0.01). Likewise, the serum levels of urea and creatinine decreased from 24.8 ± 6.5 mmol/L to 14.9 ± 8.3 mmol/L and from 278.6 ± 155.3 μmol/L to 152.6 ± 29.7 μmol/L, respectively (p < 0.05). The patients also displayed improvements in the Acute Physiology and Chronic Health Evaluation II and Glasgow scores (p < 0.05) and showed a significant reduction in hemoglobin and serum albumin levels (p < 0.05), but no obvious change in levels of platelets, alanine aminotransferase, and aspartate aminotransferase (p > 0.05).

CONCLUSION

Our results indicate that continuous veno-venous hemofiltration with gradient sodium replacement fluid is effective in treating hypernatremia in severely burned patients with the controllable sodium reduction rate and satisfactory clinical outcomes.

NFAT5 Has a Job in the Brain

Nuclear factor of activated T cells 5 (NFAT5) has recently been classified as a new member of the Rel family. In addition, there are 5 more well-defined members (NF-κB and NFAT1-4) in the Rel family, which participate in regulating the expression of immune and inflammatory response-related genes. NFAT5 was initially identified in renal medullary cells where it regulated the expression of osmoprotective-related genes during the osmotic response. Many studies have demonstrated that NFAT5 is highly expressed in the nuclei of neurons in fetal and adult brains. Additionally, its expression is approximately 10-fold higher in fetal brains. With the development of detection technologies (laser scanning confocal microscopy, transgene technology, etc.), recent studies suggest that NFAT5 is also expressed in glial cells and plays a more diverse functional role. This article aims to summarize the current knowledge regarding the expression of NFAT5, its regulation of activation, and varied biological functions in the brain.

A simple high throughput assay to evaluate water consumption in the fruit fly

Water intake is essential for survival and thus under strong regulation. Here, we describe a simple high throughput system to monitor water intake over time in Drosophila. The design of the assay involves dehydrating fly food and then adding water back separately so flies either eat or drink. Water consumption is then evaluated by weighing the water vessel and comparing this back to an evaporation control. Our system is high throughput, does not require animals to be artificially dehydrated, and is simple both in design and implementation. Initial characterisation of homeostatic water consumption shows high reproducibility between biological replicates in a variety of experimental conditions. Water consumption was dependent on ambient temperature and humidity and was equal between sexes when corrected for mass. By combining this system with the Drosophila genetics tools, we could confirm a role for ppk28 and DopR1 in promoting water consumption, and through functional investigation of RNAseq data from dehydrated animals, we found DopR1 expression in the mushroom body was sufficient to drive consumption and enhance water taste sensitivity. Together, we provide a simple high throughput water consumption assay that can be used to dissect the cellular and molecular machinery regulating water homeostasis in Drosophila.

Continuous veno-venous hemodialysis and filtration for extensive burn with severe hypernatremia

Case

A 51-year-old man presented with severe burns, with a burn index of 33.5. Relaxation incisions were made in the trunk and right arm. Ringer's solution (12,000 mL) was used as initial fluid therapy for the first 24 h. The patient's serum Na level gradually increased to 170 mEq/L; infusion was carried out to correct the hypernatremia. Continuous veno-venous hemodialysis and filtration succeeded in maintaining the serum Na level at approximately 145 mEq/L.

Outcome

After the initiation of continuous veno-venous hemodialysis and filtration, the skin graft survival rate improved markedly with the normalization of the Na level, and the patient recovered smoothly. He was discharged on foot.

Conclusion

Hypernatremia, frequently observed in patients with extensive burns, is considered to be markedly disadvantageous for the survival of skin grafts. Continuous veno-venous hemodialysis and filtration may be one of the options for the treatment of refractory hypernatremia in severe burns.

Widespread Inducible Transcription Downstream of Human Genes

Pervasive transcription of the human genome generates RNAs whose mode of formation and functions are largely uncharacterized. Here, we combine RNA-seq with detailed mechanistic studies to describe a transcript type derived from protein-coding genes. The resulting RNAs, which we call DoGs for downstream of gene containing transcripts, possess long non-coding regions (often >45 kb) and remain chromatin bound. DoGs are inducible by osmotic stress through an IP3 receptor signaling-dependent pathway, indicating active regulation. DoG levels are increased by decreased termination of the upstream transcript, a previously undescribed mechanism for rapid transcript induction. Relative depletion of polyA signals in DoG regions correlates with increased levels of DoGs after osmotic stress. We detect DoG transcription in several human cell lines and provide evidence for thousands of DoGs genome wide.

Disorders of sodium and water balance

Dysnatremias occur simultaneously with disorders in water balance. The first priority is to correct dehydration; once the patient is euvolemic, the sodium level can be reassessed. In unstable patients with hyponatremia, the clinician should rapidly administer hypertonic saline. In unstable patients with hypernatremia, the clinician should administer isotonic intravenous fluid. In stable patients with either hyponatremia or hypernatremia, the clinician should aim for correction over 24 to 48 hours, with the maximal change in serum sodium between 8 to 12 mEq/L over the first 24 hours. This rate of correction decreases the chances of cerebral edema or osmotic demyelination syndrome.

Population pharmacokinetics of tolvaptan in healthy subjects and patients with hyponatremia secondary to congestive heart failure or hepatic cirrhosis

Tolvaptan is a selective V2 -receptor antagonist used to treat hypervolemic and euvolemic hyponatremia. A population pharmacokinetic (PK) analysis was performed for tolvaptan in NONMEM® based upon data obtained from three trials conducted in 93 healthy subjects and six trials conducted in 628 congestive heart failure (CHF) patients or 24 hepatic cirrhosis patients receiving oral tolvaptan (5 to 240 mg). A two-compartment model with first-order absorption and elimination best described tolvaptan PK. Relative oral bioavailability was modeled relative to 100% for a 30 mg dose and ranged from 79.4% to 122%. Body weight and the impact of CHF or hepatic cirrhosis relative to healthy subjects were statistically significant (p < 0.001) predictors of both the apparent oral clearance (CL/F) and apparent central volume of distribution (Vc /F). The CL/F was reduced to 58.2% for New York Heart Association (NYHA) Class 1 or 2 CHF, 45.5% for NYHA Class 3 or 4 CHF, and 58.0% for hepatic cirrhosis relative to healthy subjects. Vc /F was reduced to 59.9% for NYHA Class 1 or 2 CHF and 51.3% for NYHA Class 3 or 4 CHF, and was 64.8% larger for severe hepatic cirrhosis (Child-Pugh score ≥ 10) relative to healthy subjects. A slight additional decrease in CL/F of 18.3% was also detected for patients with moderate hyponatremia (serum sodium of 115-130 mEq/l) after adjusting for CHF or cirrhosis (p < 0.001). This population PK model enabled assessment of tolvaptan PK with varying degrees of CHF and hepatic cirrhosis with fluid overload and may be used to explore PK-PD relationships with respect to fluid and electrolyte balance.

Endothelin-3 expression in the subfornical organ enhances the sensitivity of Na(x), the brain sodium-level sensor, to suppress salt intake

Salt homeostasis is essential to survival, but brain mechanisms for salt-intake control have not been fully elucidated. Here, we found that the sensitivity of Na(x) channels to [Na(+)](o) is dose-dependently enhanced by endothelin-3 (ET-3). Na(x) channels began to open when [Na(+)](o) exceeded ~150 mM without ET-3, but opened fully at a physiological [Na(+)](o) (135–145 mM) with 1 nM ET-3. Importantly, ET-3 was expressed in the subfornical organ (SFO) along with Nax, and the level was robustly increased by dehydration. Pharmacological experiments revealed that endothelin receptor B (ET(B)R) signaling is involved in this modulation of Na(x) gating through protein kinase C and ERK1/2 activation. ET(B)R agonists increased the firing rate of GABAergic neurons via lactate in the SFO, and an ET(B)R antagonist attenuated salt aversion during dehydration. These results indicate that ET-3 expression in the SFO is tightly coupled with body-fluid homeostasis through modulation of the [Na(+)](o) sensitivity of Na(x).

Acute kidney injury, sodium disorders, and hypercalcemia in the aging kidney: diagnostic and therapeutic management strategies in emergency medicine

This article summarizes the current literature regarding the structural and functional changes of the aging kidney and describes how these changes make the older patient more susceptible to acute kidney injury and fluid and electrolyte disorders. It discusses the clinical manifestations, evaluation, and management of hyponatremia and shows how the management of hypernatremia in geriatric patients involves addressing the underlying cause and safely correcting the hypernatremia. The current literature regarding evaluation and management of hypercalcemia in older patients is summarized. The management of severe hypercalcemia is discussed in detail. The evaluation and management of acute kidney injury is described.

Nuclear factor of activated T cells 5 deficiency increases the severity of neuronal cell death in ischemic injury

Nuclear factor of activated T cells 5 (NFAT5) has been implicated in regulating several genes that are thought to be neuroprotective in ischemic injury. Because of the embryonic lethality of NFAT5 knockout (NFAT5(-/-)) mice, the heterozygous (NFAT5(+/-)) mice were used to study the in vivo role of NFAT5 in hypoxia/ischemia (H/I) condition. The NFAT5(+/-) mice exhibited more severe neurological deficits, larger infarct area and edema formation associated with increased aquaporin 4 expressions in the brain. Under in vitro H/I condition, increased apoptotic cell death was found in NFAT5(-/-) neurons. Moreover, SMIT, a downstream to NFAT5, was upregulated in NFAT5(+/+) neurons, while the SMIT level could not be upregulated in NFAT5(-/-) neurons under H/I condition. The elevation of reactive oxygen species generation in NFAT5(-/-) neurons under H/I condition further confirmed that NFAT5(-/-) neurons were more susceptible to oxidative stress. The present study demonstrated that activation of NFAT5 and its downstream SMIT induction is important in protecting neurons from ischemia-induced oxidative stress.

Progressive fluid removal can avoid electrolyte disorders in severely burned patients

INTRODUCTION

Extensive burn injury has systemic consequences due to capillary leak. After restoration of cellular integrity, infused fluid volume has to be removed partially. This can provoke electrolyte disorders.

PURPOSE

We investigated the effect of progressive fluid removal on serum sodium level.

METHOD

Retrospective study. Patients admitted to a burn unit were analyzed and separated in two groups without (Group A) or with (Group B) prolonged hypernatremia. Daily infusion-diuresis-ratio (IDR) was analyzed.

RESULTS

Fourty (12 female; 28 male) patients with a mean age of 47±19 years, a total burn surface area (TBSA) of 26±12%, and a mean abbreviated burned severity index (ABSI) score of 7.3±2 were included. In Group A 25 patients with a mean age of 47±18 years, a mean TBSA of 23±11%, and a mean ABSI score of 6.9±2.1 were summarized. In Group B 15 patients with a mean age of 47±22 years, a mean TBSA of 30±13%, and a mean ABSI score of 8.1±1.7 were included. Hypernatremia occurred on day 5±1.4. There was no significant difference between both groups for fluid resuscitation amount within the first 24 hours. Statistical analysis of the first 7 days after burn injury showed a significantly higher percentage of removed fluid in Group B for day 3, day 4, day 5, day 6 and day 7.

CONCLUSIONS

Amount and velocity of fluid removal regimen after burn injury can provoke electrolyte disorders. Serum sodium concentration can be used to calculate need of fluid resuscitation for fluid maintenance. There is a need of an established fluid removal strategy.

Does hypernatremia impact mortality in Toxic Epidermal Necrolysis?

Introduction: In-hospital hypernatremia is associated with increased mortality rates. We want to elucidate the impact of in-hospital acquired hypernatremia in mortality of Toxic Epidermal Necrolysis (TEN).

Purpose: Is there an association between hypernatremia and mortality in patients with TEN?

Method: Retrospective study of 25 patients with TEN. Laboratory electrolyte results, diuresis and survival were analyzed. Patients were separated in two groups without (Group A) or with (Group B) hypernatremia.

Results: In Group A 10 patients with a TBSA of 74±25% (mean ± standard deviation), and a SCORTEN-Score of 2.7±0.9 were summarized. Diuresis within the first 10 days after admission was 1±0.3 ml/kg/hour. In Group B 15 patients with a TBSA of 76±19%, and a SCORTEN-Score of 3.5±1 were included. Diuresis within the first 10 days after admission was 1.4±0.4 ml/kg/hour. Hypernatremia occurred on day 3.3±2.4 after admission and persisted for 5.3±2.9 days. Statistical analysis showed a significantly higher diuresis (p=0.007) and SCORTEN-Score (p=0.04) in the hypernatremic patients. One normonatremic and 8 hypernatremic patients died during ICU-stay (overall mortality rate 36%). A significantly higher mortality rate was found in Group B (odds ratio: 13,5; 95% confidence interval: 1.34–135.98; p=0.01) during ICU-stay.

Conclusion: TEN patients with an in-hospital acquired hypernatremia have an increased mortality risk. Close electrolyte monitoring is advisable in these patients.

Transdermal fluid loss in severely burned patients

INTRODUCTION

The skin protects against fluid and electrolyte loss. Burn injury does affect skin integrity and protection against fluid loss is lost. Thus, a systemic dehydration can be provoked by underestimation of fluid loss through burn wounds.

PURPOSE

We wanted to quantify transdermal fluid loss in burn wounds.

METHOD

Retrospective study. 40 patients admitted to a specialized burn unit were analyzed and separated in two groups without (Group A) or with (Group B) hypernatremia. Means of daily infusion-diuresis-ratio (IDR) and the relationship to totally burned surface area (TBSA) were analyzed.

RESULTS

In Group A 25 patients with a mean age of 47 ± 18 years, a mean TBSA of 23 ± 11%, and a mean abbreviated burned severity index (ABSI) score of 6.9 ± 2.1 were summarized. In Group B 15 patients with a mean age of 47 ± 22 years, a mean TBSA of 30 ± 13%, and a mean ABSI score of 8.1 ± 1.7 were included. Statistical analysis of the period from day 3 to day 6 showed a significant higher daily IDR-amount in Group A (Group A vs. Group B: 786 ± 1029 ml vs. -181 ± 1021 ml; p<0.001) and for daily IDR-TBSA-ratio (Group A vs. Group B: 40 ± 41 ml/% vs. -4 ± 36 ml/%; p<0.001).

CONCLUSIONS

There is a systemic relevant transdermal fluid loss in burn wounds after severe burn injury. Serum sodium concentration can be used to calculate need of fluid resuscitation for fluid maintenance. There is a need of an established fluid removal strategy to avoid water and electrolyte imbalances.

Hyponatremia and the syndrome of inappropriate secretion of antidiuretic hormone (SIADH)

The syndrome of inappropriate ADH secretion (SIADH), also recently referred to as the "syndrome of inappropriate antidiuresis", is an often underdiagnosed cause of hypotonic hyponatremia, resulting for instance from ectopic release of ADH in lung cancer or as a side-effect of various drugs. In SIADH, hyponatremia results from a pure disorder of water handling by the kidney, whereas external Na+ balance is usually well regulated. Despite increased total body water, only minor changes of urine output and modest edema are usually seen. Renal function and acid-base balance are often preserved, while neurological impairment may range from subclinical to life-threatening. Hypouricemia is a distinguishing feature. The major causes and clinical variants of SIADH are reviewed, with particular emphasis on iatrogenic complications and hospital-acquired hyponatremia. Effective treatment of SIADH with water restriction, aquaretics, or hypertonic saline + loop diuretics, as opposed to worsening of hyponatremia during parenteral isotonic fluid administration, underscores the importance of an early accurate diagnosis and careful follow-up of these patients.

Autoimmunity to the sodium-level sensor in the brain causes essential hypernatremia

Na(x) is the sodium-level sensor of body fluids in the brain involved in sodium homeostasis. Na(x)-knockout mice do not stop ingesting salt even when dehydrated. Here we report a case with clinical features of essential hypernatremia without demonstrable hypothalamic structural lesions, who was diagnosed as a paraneoplastic neurologic disorder. The patient had autoantibodies directed against Na(x), along with a ganglioneuroma composed of Schwann-like cells robustly expressing Na(x). The removal of the tumor did not reduce the autoantibody levels or relieve the symptoms. Intravenous injection of the immunoglobulin fraction of the patient's serum into mice induced abnormalities in water/salt intake and diuresis, which led to hypernatremia. In the brains of these mice, cell death was observed along with focal deposits of complement C3 and inflammatory infiltrates in circumventricular organs where Na(x) is specifically expressed. Our findings thus provide new insights into the pathogenesis of hypernatremia relevant to the sodium-level-sensing mechanism in humans.

Increased mortality in hypernatremic burned patients

Introduction: In-hospital hypernatremia develops usually iatrogenically from inadequate or inappropriate fluid prescription. In severely burned patient an extensive initial fluid resuscitation is necessary for burn shock survival. After recovering of cellular integrity the circulating volume has to be normalized. Hereby extensive water and electrolyte shifts can provoke hypernatremia.

Purpose: Is a hypernatremic state associated with increased mortality?

Method: Retrospective study for the incidence of hypernatremia and survival in 40 patients with a totally burned surface area (TBSA) >10%. Age, sex, TBSA, ABSI-Score and fluid resuscitation within the first 24 hours were analyzed. Patients were separated in two groups without (Group A) or with (Group B) hypernatremia.

Results: Hypernatremia occurred on day 5±1.4. No significant difference for age, sex, TBSA, ABSI-Score and fluid resuscitation within the first 24 hours were calculated. In Group A all patients survived, while 3 of the hypernatremic patient in Group B died during ICU-stay (Odds-ratio = 1.25; 95% CI 0.971–1.61; p=0.046).

Conclusion: Burned patients with an in-hospital acquired hypernatremia have an increased mortality risk. In case of a hypernatremic state early intervention is obligatory. There is a need of a fluid removal strategy in severely burned patient to avoid water imbalance.

[Incidence of hyponatremia and its causes in neurological patients]

INTRODUCTION

Hyponatremia is considered the most frequent electrolyte disorder found in hospitalized patients and seems to be a prognostic factor during hospitalization.

METHODS

A prospective observational study was carried out in consecutive neurological patients admitted to our hospital over a 3-month period. Blood and urinary ionogram and osmolality were determined at entry and 3-5 days after admission in all patients with hyponatremia.

RESULTS

Of the 130 patients admitted, 19 (14.6%) had hyponatremia. The causes of hyponatremia were as follows: inappropriate fluid replacement in 4 patients (21%), antihypertensive drugs in 4 (21%), syndrome of inappropriate secretion of antidiuretic hormone in 4 (21%), cerebral salt wasting syndrome in 2 (10%), and edematous status caused by liver disease in one and digestive loss in one (5%) each. Mortality was one (5%) and 0 (0%) among patients with and without hyponatremia, respectively.

CONCLUSION

Hyponatremia is common in hospitalized neurological patients and can be misdiagnosed as a worsening of the main illness.

eIF2alpha phosphorylation tips the balance to apoptosis during osmotic stress

Regulation of cell volume is of great importance because persistent swelling or shrinkage leads to cell death. Tissues experience hypertonicity in both physiological (kidney medullar cells) and pathological states (hypernatremia). Hypertonicity induces an adaptive gene expression program that leads to cell volume recovery or apoptosis under persistent stress. We show that the commitment to apoptosis is controlled by phosphorylation of the translation initiation factor eIF2alpha, the master regulator of the stress response. Studies with cultured mouse fibroblasts and cortical neurons show that mutants deficient in eIF2alpha phosphorylation are protected from hypertonicity-induced apoptosis. A novel link is revealed between eIF2alpha phosphorylation and the subcellular distribution of the RNA-binding protein heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1). Stress-induced phosphorylation of eIF2alpha promotes apoptosis by inducing the cytoplasmic accumulation of hnRNP A1, which attenuates internal ribosome entry site-mediated translation of anti-apoptotic mRNAs, including Bcl-xL that was studied here. Hypertonic stress induced the eIF2alpha phosphorylation-independent formation of cytoplasmic stress granules (SGs, structures that harbor translationally arrested mRNAs) and the eIF2alpha phosphorylation-dependent accumulation of hnRNP A1 in SGs. The importance of hnRNP A1 was demonstrated by induction of apoptosis in eIF2alpha phosphorylation-deficient cells that express exogenous cytoplasmic hnRNP A1. We propose that eIF2alpha phosphorylation during hypertonic stress promotes apoptosis by sequestration of specific mRNAs in SGs in a process mediated by the cytoplasmic accumulation of hnRNP A1.

Iatrogenic water intoxication after pelvic ultrasonography imaging

Ultrasound (US) is a simple, easily accessible, and noninvasive method. Thus, it is commonly used. The bladder should be sufficiently filled to acquire pelvic images by US. This report describes water poisoning in 3 patients with no hepatic, cardiac, or renal disease. Both patients had a history of excessive fluid intake.

Assessment of the efficacy and safety of intravenous conivaptan in patients with euvolaemic hyponatraemia: subgroup analysis of a randomized, controlled study

OBJECTIVE AND DESIGN

Most cases of euvolaemic hyponatraemia are associated with elevated plasma levels of AVP. Conivaptan is a high-affinity, nonpeptide vasopressin V(1A)/V(2)-receptor antagonist. We performed a subgroup analysis of a multicentre, randomized, placebo-controlled, double-blind, parallel-group study to evaluate the efficacy and safety of intravenous (i.v.) conivaptan for the treatment of euvolaemic hyponatraemia.

PATIENTS

Fifty-six euvolaemic patients with serum [Na(+)] of 115 to < 130 mmol/l received conivaptan 40 or 80 mg/day or placebo via continuous i.v. infusion for 4 days. A 20-mg loading dose was administered intravenously over 30 min in the conivaptan groups; the placebo group received a placebo loading dose.

MEASUREMENTS

Change in serum [Na(+)], measured by the baseline-adjusted area under the serum [Na(+)]-time curve (AUC), was the primary efficacy parameter. Secondary efficacy measures included the time from the first dose to a confirmed > or = 4 mmol/l increase in serum [Na(+)], total time with serum [Na(+)] > or = 4 mmol/l above baseline, change in serum [Na(+)] from baseline, and number of patients with a confirmed > or = 6 mmol/l increase in serum [Na(+)] or normal [Na(+)]. Safety assessments included adverse events (AE), incidence of overly rapid correction of serum [Na(+)], and changes in vital signs and electrocardiographic and clinical laboratory parameters.

RESULTS

During the first 2 days of treatment, and over the entire 4-day treatment period, both conivaptan doses significantly increased the serum [Na(+)] AUC more than placebo (P < 0.01). Conivaptan 40 and 80 mg/day significantly improved all secondary efficacy measures. Conivaptan was generally well tolerated; infusion-site reaction was the most common AE.

CONCLUSIONS

In hospitalized patients with euvolaemic hyponatraemia, i.v. conivaptan significantly increased serum [Na(+)] promptly and was well tolerated.

Gene expression profiling in brain following acute systemic hypertonicity: novel genes possibly involved in osmoadaptation

In brain osmoprotective genes known to be involved in cellular osmoadaptation to hypertonicity, as well as the related transcription factor tonicity-responsive enhancer binding protein (TonEBP) are only expressed in some cell subsets. In the search for other genes possibly involved in osmoadaptation of brain cells we have analyzed, through microarray, the transcriptional profile of forebrain from rats subjected to 45 min, 90 min, and 6 h systemic hypertonicity. Microarray data were validated by quantitative real-time PCR. Around 23 000 genes gave a reliable hybridization signal. The number of genes showing a higher expression increased from around 15 (45 min) up to nearly 200 (6 h). Among about 30 immediate early genes (IEGs) encoding transcription factors, only Atf3, Verge, and Klf4 showed a rapid increased expression. TonEBP-mRNA tissue level and TonEBP-mRNA labeling in neurons remained unchanged whereas TonEBP labeling was rapidly increased in neurons. Sodium-dependent neutral amino acid transporter-2 (SNAT2) encoded by gene Slc38a2 showed a delayed increased expression. The rapid tonicity-induced activation of Atf3, Verge, and Klf4 may regulate genes involved in osmoadaptation. Nfat5 encoding TonEBP is not an IEG and the early tonicity-induced expression of TonEBP in neurons may result from translational activation. Increased expression of sodium-dependent neutral amino-acid transporter 2 may lead to the cellular accumulation of amino acids for adaptation to hypertonicity.

SSRIs and the syndrome of inappropriate antidiuretic hormone secretion

Selective serotonin reuptake inhibitors, which include some of the mostly widely prescribed drugs in the United States, produce fewer adverse effects than other types of antidepressants. But their use can be associated with disruption of the action of antidiuretic hormone in the body, which wreaks havoc with homeostasis. This may lead to the syndrome of inappropriate antidiuretic hormone secretion (SIADH), which is characterized by hyponatremia, a potentially fatal condition that is typically asymptomatic until it becomes severe. SIADH is more likely in some populations, including people who are elderly or who take diuretics. Serum sodium levels should be monitored closely in those at higher risk.

N/A

N/A