The kidney collecting duct is an important renal tubular segment for the regulation of body water and salt homeostasis. Water reabsorption in the collecting duct cells is regulated by arginine vasopressin (AVP) via the vasopressin V2- receptor (V2R). AVP increases the osmotic water permeability of the collecting duct cells through aquaporin-2 (AQP2) and aquaporin-3 (AQP3). AVP induces the apical targeting of AQP2 and transcription of AQP2 gene in the kidney collecting duct principal cells. The signaling transduction pathways resulting in the AQP2 trafficking to the apical plasma membrane of the collecting duct principal cells, include AQP2 phosphorylation, RhoA phosphorylation, actin depolymerization and calcium mobilization, and the changes of AQP2 protein abundance in water balance disorders have been extensively studied. These studies elucidate the underlying cellular and molecular mechanisms of body water homeostasis and provide the basis for the treatment of body water balance disorders.

• Arginine vasopressin
• Aquaporins
• Body water balance

Hypertension is a complex trait determined by both genetic and environmental factors and is a major public health problem due to its high prevalence and concomitant increase in the risk for cardiovascular disease. With the recent large increase of dietary salt intake in most developed countries, the prevalence of hypertension increases tremendously which is about 30% of the world population. There is substantial evidence that suggests some people can effectively excrete high dietary salt intake without an increase in arterial BP, and another people cannot excrete effectively without an increase in arterial BP. Salt sensitivity of BP refers to the BP responses for changes in dietary salt intake to produce meaningful BP increases or decreases. The underlying mechanisms that promote salt sensitivity are complex and range from genetic to environmental influences. The phenotype of salt sensitivity is therefore heterogeneous with multiple mechanisms that potentially link high salt intake to increases in blood pressure. Moreover, excess salt intake has functional and pathological effects on the vasculature that are independent of blood pressure. Epidemiologic data demonstrate the role of high dietary salt intake in mediating cardiovascular and renal morbidity and mortality. Almost five decades ago, Guyton and Cole- man proposed that whenever arterial pressure is elevated, pressure natriuresis enhances the excretion of sodium and water until blood volume is reduced sufficiently to return arterial pressure to control values. According to this hypothesis, hypertension can develop only when something impairs the excretory ability of sodium in the kidney. However, recent studies suggest that nonosmotic salt accumulation in the skin interstitium and the endothelial dysfunction which might be caused by the deterioration of vascular endothelial glycocalyx layer (EGL) and the epithelial sodium channel on the endothelial luminal surface (EnNaC) also play an important role in nonosmotic storage of salt. These new concepts emphasize that sodium homeostasis and salt sensitivity seem to be related not only to the kidney malfunction but also to the endothelial dysfunction. Further investigations will be needed to assess the extent to which changes in the sodium buffering capacity of the skin interstitium and develop the treatment strategy for modulating the endothelial dysfunction.

• Salt
• Sensitivity
• Hypertension
• Kidney malfunction
• Endothelial dysfunction

Diuretics are commonly used to control edema across various clinical fields. iuretics inhibit sodium reabsorption in specific renal tubules, resulting in increased rinary sodium and water excretion. Loop diuretics are the most potent iuretics. In this article, we review five important aspects of loop diuretics, in articular furosemide, which must be considered when prescribing this medicine: 1) oral versus intravenous treatment, (2) dosage, (3) continuous versus olus infusion, (4) application in chronic kidney disease patients, and (5) side ffects. The bioavailability of furosemide differs between oral and intravenous herapy. Additionally, the threshold and ceiling doses of furosemide differ according o the particular clinical condition of the patient, for example in patients ith severe edema or chronic kidney disease. To maximize the efficiency of furosemide, a clear understanding of how the mode of delivery will impact bioavailability and the required dosage is necessary.

• Loop diuretics
• Furosemide
• Chronic kidney disease

Background: The relationship between abdominal obesity (AO) and mortality in peritoneal dialysis (PD) patients is controversial. Methods: The prevalence of AO in 84 PD patients was assessed in a cross- section manner and followed up for 9 years at a single center. AO was defined as a waist circumference (WC) of more than 90 cm in males or more than 80 cm in females. The patients were classified as either with AO(AO group) or without AO(nAO group). Results: The AO group was older, contained more diabetics, more females, and had higher Charlson comorbidity index (aCCI) scores, BMI, and triglyceride and lower serum creatinine than the non-AO subjects. The follow-up duration was 53.2±34.4 months. At the end of the follow-up, eighteen patients (21.4%) were dead; 9 died of cardiovascular causes. The five year survival rate was 40.8%. Kaplan-Meier analysis revealed that both all-cause and cardiovascular- cause mortalities were similar in the AO and nAO groups. Multivariate analysis revealed the presence of AO not to be an independent risk factor of all-cause and cardiovascular-cause mortality. Conclusion: AO itself might not be a risk factor for mortality in PD patients. Nevertheless, further prospective studies with a large number of patients will be needed to prove this.

• Abdominal obesity
• Continuous ambulatory peritoneal dialysis
• Mortality
• Risk factors
• Chronic kidney failure

Osmotic demyelination syndrome is a demyelinating disorder associated with rapid correction of hyponatremia. But, it rarely occurs in acute hypernatremia, and it leads to permanent neurologic symptoms and is associated with high mortality. A 44-year-old woman treated with alternative medicine was admitted with a history of drowsy mental status. Severe hypernatremia (197mEq/L) with hyperosmolality (415mOsm/kgH2O) was evident initially and magnetic resonance imaging revealed a high signal intensity lesion in the pons, consistent with central pontine myelinolysis. She was treated with 0.45% saline and 5% dextrose water and intravenous corticosteroids. Serum sodium normalized and her clinical course gradually improved. Brain lesion of myelinolysis also improved in a follow-up imaging study. This is the first report of a successful treatment of hypernatremia caused by iatrogenic salt intake, and it confirms the importance of adequate fluid supplementation in severe hypernatremia.

• Hypernatremia
• Osmotic demyelination syndrome
• Magnetic resonance imaging