The recently discovered angiotensin-converting enzyme-related carboxypeptidase 2 (ACE2)-[Angiotensin-(1-7)(Ang-(1-7)]-Mas receptor axis has an opposing function to that of the ACE-Angiotensin II (Ang II)-Angiotensin type 1 (AT1) receptor axis. Ang-(1-7) is present in the kidneys at concentrations comparable to those of Ang II and is associated with vasodilation, modulation of sodium and water transport, and stimulation of nitric oxide (NO) synthase. Ang-(1-7) also acts as a physiological antagonist of Ang II by counterbalancing the Ang IImediated intracellular signaling pathway. In a hypertensive model, increased ACE and decreased ACE2 along with a higher ACE/ACE2 ratio in hypertensive kidneys appeared to favor Ang II generation, leading to hypertensive renal damage. In addition, the administration of a selective Ang-(1-7) receptor blocker or an ACE2 inhibitor was associated with worsening of hypertension and renal function. Ang-(1-7)-mediated increases in renal blood flow were abolished by blockade of the Mas receptor and by inhibition of prostaglandin release and NO in spontaneously hypertensive rats and in Wistar-Kyoto controls. Further research on the function of the ACE2-Ang-(1-7)-Mas receptor axis could lead to a novel target for inhibiting kidney disease progression.

• ACE
• ACE2
• angiotensin II
• angiotensin-(1-7)

Renal ammonia metabolism is the predominant component of net acid excretion and new bicarbonate generation. Renal ammonia metabolism is regulated by acid-base balance. Both acute and chronic acid loads enhance ammonia production in the proximal tubule and secretion into the urine. In contrast, alkalosis reduces ammoniagenesis. Hypokalemia is a common electrolyte disorder that significantly increases renal ammonia production and excretion, despite causing metabolic alkalosis. Although the net effects of hypokalemia are similar to metabolic acidosis, molecular mechanisms of renal ammonia production and transport have not been well understood. This mini review summarizes recent findings regarding renal ammonia metabolism in response to chronic hypokalemia.

• kidney
• ammonia
• acids
• hypokalemia

Hyponatremia is the most common electrolyte disorder in hospitalized patients. Many studies documented that it was related to increased morbidity and mortality in patients with congestive heart failure, liver cirrhosis, and neurologic diseases. Although knowledge of hyponatremia has been cumulated, the optimal management of hyponatremia remains incompletely established in clinical practice because of the diversity of underlying disease states, and its multiple causes with differing pathophysiologic mechanisms. Since vasopressin receptor antagonists have unique aquaretic effect to selectively increase electrolytesfree water excretion, clinicians could apply a more effective method to treat hyponatremia. Tolvaptan has significant evidence that it improves serum sodium levels in patients with euvolemic or hypervolemic hyponatremia related with heart failure, cirrhosis or syndrome of inappropriate antidiuretic hormone. Tolvaptan has acceptable safety and tolerability for longterm usage in chronic hyponatremia, and the beneficial effects on serum Na+ occurred in patients with both mild and marked hyponatremia.

• tolvaptan
• hyponatremia
• arginine vasopressin receptors

Proteinuria is a major promoter that induces tubulointerstitial injury in glomerulopathy. Dietary salt restriction may reduce proteinuria, although the mechanism is not clear. We investigated the effects of dietary salt restriction on rat kidneys in an animal model of glomerular proteinuria. Male SpragueDawley rats were used and divided into 3 groups: vehicletreated normalsalt controls, puromycin aminonucleoside (PA)­treated normalsalt rats, and PAtreated lowsalt rats. PA was given at a dose of 150 mg/kg BW at time 0, followed by 50 mg/kg BW on days 28, 35, and 42. Sodiumdeficient rodent diet with and without additional NaCl (0.5%) were provided for normalsalt rats and lowsalt rats, respectively. On day 63, kidneys were harvested for histopathologic examination and immunohistochemistry. PA treatment produced overt proteinuria and renal damage. Dietary salt restriction insignificantly reduced proteinuria in PAtreated rats, and PAtreated lowsalt rats had lower urine output and lower creatinine clearance than vehicletreated normalsalt controls. When tubulointerstitial injury was semiquantitatively evaluated, it had a positive correlation with proteinuria. The tubulointerstitial injury score was significantly increased by PA treatment and relieved by lowsalt diet. ED1positive infiltrating cells and immunostaining for interstitial collagen III were significantly increased by PA treatment. These changes appeared to be less common in PAtreated lowsalt rats, although the differences in PAtreated normalsalt versus lowsalt rats did not reach statistical significance. Our results suggest that renal histopathology in PA nephrosis may potentially be improved by dietary salt restriction. Nonhemodynamic mechanisms induced by lowsodium diet might contribute to renoprotection.

• puromycin
• diet
• sodiumrestricted
• proteinuria
• kidney

Accurate measurement of the volume status in hemodialysis patients is important as it can affect mortality. However, no studies have been conducted regarding volume management in cases where a sudden change of body fluid occurs, such as during puerperium in hemodialysis patients. This report presents a case in which the patient was monitored for her body composition and her volume status was controlled using a body composition monitor (BCM) during the puerperal period. This case suggests that using a BCM for volume management may help maintain hemodynamic stability in patients with a rapidly changing volume status for a short term period, such as during puerperium.

• body composition
• hemodialysis
• postpartum period
• volume control