PAST ISSUES

Membrane Trafficking of Collecting Duct Water Channel Protein AQP2 Regulated by Akt/AS160

Hyun Jun Jung, Tae Hwan Kwon

Akt (protein kinase B (PKB)) is a serine/threonine kinase that acts in the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway. The PI3K/ Akt signaling pathway, triggered by growth factors and hormones including vasopressin, is an important pathway that is widely involved in cellular mechanisms regulating transcription, translation, cell growth and death, cell proliferation, migration, and cell cycles. In particular, Akt and Akt substrate protein of 160 kDa (AS160) are likely to participate in the trafficking of aquaporin-2 (AQP2) in the kidney collecting duct. In this study, we demonstrated that 1) small interfering RNA (siRNA)-mediated gene silencing of Akt1 significantly decreased Akt1 and phospho-AS160 protein expression; and 2) confocal laser scanning microscopy of AQP2 in mouse cortical collecting duct cells (M-1 cells) revealed AS160 knockdown by siRNA increased AQP2 expression in the plasma membrane compared with controls, despite the absence of dDAVP stimulation. Thus, the results suggest that PI3K/Akt pathways could play a role in AQP2 trafficking via the AS160 protein

  • Electrolytes & Blood Pressure Vol.8:59-65, 7 Pages, 2010

Acid-Base Disorders in ICU Patients

Yun Kyu Oh

Metabolic acid-base disorders are comnom clinical problems in ICU patients. Arterial blood gas analysis and anion gap (AG) are important laboratory data in approaching acid-base interpretation. When measuring the AG, several factors such as albumin have influence on unmeasured anions and unmeasured cations. If a patient has hypoalbuminemia, the AG should be adjusted according to the albumin level. High AG metabolic acidoses including lactic acidosis, ketoacidosis, and ingestion of toxic alcohols are common in ICU patients. The treatment target of lactic acidosis and ketoacidosis is not the acidosis, but the underlying condition causing acidosis. Gastric acid loss, diuretics, volume depletion, renal compensation for respiratory acidosis, hypokalemia, and mineralocorticoid excess are common causes of metaboic alkalosis. In chloride responsive metaboic alkalosis, volume and potassium repletion are mandatory.

  • Electrolytes & Blood Pressure Vol.8:66-71, 6 Pages, 2010

Fluid and Electrolyte Disturbances in Critically Ill Patients

Jay Wook Lee

Disturbances in fluid and electrolytes are among the most common clinical problems encountered in the intensive care unit (ICU). Recent studies have reported that fluid and electrolyte imbalances are associated with increased morbidity and mortality among critically ill patients. To provide optimal care, health care providers should be familiar with the principles and practice of fluid and electrolyte physiology and pathophysiology. Fluid resuscitation should be aimed at restoration of normal hemodynamics and tissue perfusion. Early goaldirected therapy has been shown to be effective in patients with severe sepsis or septic shock. On the other hand, liberal fluid administration is associated with adverse outcomes such as prolonged stay in the ICU, higher cost of care, and increased mortality. Development of hyponatremia in critically ill patients is associated with disturbances in the renal mechanism of urinary dilution. Removal of nonosmotic stimuli for vasopressin secretion, judicious use of hypertonic saline, and close monitoring of plasma and urine electrolytes are essential components of therapy. Hypernatremia is associated with cellular dehydration and central nervous system damage. Water deficit should be corrected with hypotonic fluid, and ongoing water loss should be taken into account. Cardiac manifestations should be identified and treated before initiating stepwise diagnostic evaluation of dyskalemias. Divalent ion deficiencies such as hypocalcemia, hypomagnesemia and hypophosphatemia should be identified and corrected, since they are associated with increased adverse events among critically ill patients.

  • Electrolytes & Blood Pressure Vol.8:72-81, 10 Pages, 2010

Recent Advances of Oral Rehydration Therapy (ORT)

Jin Soon Suh, Won Ho Hahn, Byoung Soo Cho

Diarrheal disease is one of the leading causes of worldwide morbidity and mortality, especially in children. It causes loss of body fluid, which may lead to severe dehydration, electrolyte imbalance, shock and even to death. The mortality rate from acute diarrhea has decreased over the last few decades. This decline, especially in developing countries is largely due to the implantation of the standard World Health Organization-oral rehydration solution (WHOORS). However, the use of standard ORS has been limited by its inability to reduce fecal volume or diarrhea duration. Subsequently, this has led to various attempts to modify its compositions. And these modifications include the use of reduced osmolarity ORS, polymer-based ORS and zinc supplementation. Some of these variations have been successful and others are still under investigation. Therefore, further trials are needed to progress toward the ideal ORS. In this article, we briefly reviewed the pathophysiologic basis of the ORS, followed by the standard WHO-ORS and several modifications to improve the ORS.

  • Electrolytes & Blood Pressure Vol.8:82-86, 5 Pages, 2010

Atherosclerotic Renovascular Hypertension: Lessons from Recent Clinical Studies

Woo Kyung Chung, Se Joong Kim

Atherosclerotic renovascular hypertension is a form of secondary hypertension due to renal artery stenosis. After the introduction of medical therapy such as with statins and angiotensin blocking agents, it has been considered a very slowly progressive disease. In the 1990s, surgical methods were compared to radiological intervention and showed no additional benefits. Recent clinical data also demonstrate that in cases of relatively stable atherosclerotic renovascular disease, medical therapy is as effective as other interventions with regard to patient outcomes. In this paper the recent clinical outcomes are reviewed.

  • Electrolytes & Blood Pressure Vol.8:87-91, 5 Pages, 2010

Hypercalcemia Associated with Acute Kidney Injury and Metabolic Alkalosis

Jong Hyeok Jeong, Eun Hui Bae

Most cases of hypercalcaemia are secondary to malignancy or primary hyperparathyroidism. We report a patient presenting with a triad of hypercalcemia, metabolic alkalosis, and renal failure secondary to treatment of iatrogenic hypoparathyroidism and osteoporosis. Persistent ingestion of calcium carbonate and vitamin D caused milk-alkali syndrome. The patient was managed with intravenous fluids and withdrawal of calcium carbonate and vitamin D. She responded well to the treatment and the calcium concentration, renal function and metabolic alkalosis were normalized. Milk-alkali syndrome may be important as a reemerging cause of hypercalcemia.

  • Electrolytes & Blood Pressure Vol.8:92-94, 3 Pages, 2010