Plasma calcium concentration is maintained within a narrow range (8.5-10.5 mg/dL) by the coordinated action of parathyroid hormone (PTH), 1,25(OH)2D3, calcitonin, and ionized calcium (iCa2+) itself. The kidney plays a key role in this process by the fine regulation of calcium excretion. More than 95% of filtered calcium is reabsorbed along the renal tubules. In the proximal tubules, 60% of filtered calcium is reabsorbed by passive mechanisms. In the thick ascending limb, 15% of calcium is reabsorbed by paracellular diffusion through paracellin-1 (claudin-16). The calcium sensing receptor (CaSR) in the basolateral membrane of the thick ascending limb senses the change in iCa2+ and inhibits calcium reabsorption independent to PTH and 1,25(OH)2D3. The fine regulation of calcium excretion occurs in the distal convoluted tubules and connecting tubules despite the fact that only 10-15% of filtered calcium is reabsorbed there. Transient receptor potential vanilloid 5 (TRPV5) and 6 (TRPV6) in the apical membrane act as the main portal of entry, calbindin-D28K delivers Ca2+ in the cytoplasm, and then Na2+/Ca2+ exchanger (NCX1) and plasma membrane Ca2+-ATPase in the basolateral membrane serve as an exit. In the cortical collecting duct, TRPV6 is expressed, but the role might be negligible. In addition to PTH and 1,25(OH)2D3, acid-base disturbance, diuretics, and estrogen affect on these calcium channels. Recently, klotho and fibroblast growth factor 23 (FGF23) are suggested as new players in the calcium metabolism. Klotho is exclusively expressed in the kidney and co-localized with TRPV5, NCX1, and calbindin-D28K. Klotho increases calcium reabsorption through trafficking of TRPV5 to the plasma membrane, and also converts FGF receptor to the specific FGF23 receptor. FGF23:klotho complex bound to FGF receptor inhibits 1alpha- hydroxylase of vitamin D, and contributes to calcium reabsorption and phosphate excretion in the kidney.
Calcitonin ; Calcium ; Calcium Channels ; Calcium-Binding Protein, Vitamin D-Dependent ; Cell Membrane ; Cytoplasm ; Diffusion ; Diuretics ; Estrogens ; Extremities ; Fibroblast Growth Factors ; Homeostasis ; Kidney ; Membranes ; Parathyroid Hormone ; Plasma ; Receptors, Calcium-Sensing ; Receptors, Fibroblast Growth Factor ; TRPV Cation Channels ; Vitamin D

Diuretic drugs are the most commonly used agents to control edema or volume overload. However, the clinical use of diuretics is not confined to edema control. Recently, diuretics have been revisited for the management of various diseases, including hypertension and congestive heart failure. Diuretics are classified mainly by their sites of action in the renal tubules, and have unique characteristics and adverse effects according to their mechanisms of action. To use diuretics adequately, it is very important to understand their characteristics.
Diuretics ; Edema ; Heart Failure ; Hypertension

Hypematremia is a rare but important medical condition and is associated with mortality rate of 40 to 70%. However, little has been known about its prognostic factors or treatment guidlines. To evaluate the prognostic factors and the outcome following treatment, we reviewed 22 available medical records among twenty five hypernatremic patients (0.2%) in 12841 admissions at medical ward from January to December 1995. We defined hypernatremia as serum sodium concentration more than or equal to 150 mEq/L. Of these patients, two had hypematrernia at admission and the remaining patients became hypernatremic during admission. Mean peak serum sodium concentration was 158 (150-178) mEq/L and mean total body water deficit was 11.4 (6.7-21.3)%. Factors correlated with the development of hypernatremia were diverse and multiple, and the most frequent factor was diminished access to water. Mortality rate was 59%, but mortality was not correlated with age, correction rate of hyper-natremia, primary route of fluid loss, and the severity of hypernatremia or total body water deficit. Mortality rate was higher in patients whose serum sodium concentrations were below 130 mEq/L at admission (P<0.05). In our study, development of hypernatremia from initial hyponatremic state was significantly associated with poor outcome, and age, rapidity of correction, route of fluid loss, and the severity of hypernatremia or total body water deficit were not.
Body Water ; Humans ; Hypernatremia* ; Medical Records ; Mortality ; Sodium ; Water

The aim of this cross-over study was to investigate whether albumin infusion before furosemide administration could potentiate the diuretic action of furosemide. Seven patients with nephrotic syndrome were given the following infusions in random order on two separate days: 1) a sham solution followed by 160 mg of furosemide, 2) 100 ml of 20% human albumin followed by 160 mg of furosemide. Urine and serum furosemide concentrations were measured by high-performance liquid chromatography. The increment of urine volume was greater in albumin preinfusion than in furosemide alone. However, the increments of sodium and chloride excretions between furosemide alone and albumin preinfusion were not different. No significant differences in the pharmacokinetic parameters between the two treatments were observed: area under the concentration-time curve (AUC: 12.7+/-2.2 vs 15.1+/-4.4 g/ml hr), total plasma clearance (253+/-41 vs 256+/-54 ml/min), volume of distribution (341+/-34 vs 494+/-153 ml/kg), elimination half life (4.0+/-1.1 vs 4.6+/-0.8 hr), and urine furosemide excretion of the administered amount (16.5+/-7.3 vs 7.5+/-1.6%). In conclusion, these data show that albumin preinfusion potentiated diuresis, but not natriuresis, of furosemide without any change in the pharmacokinetics of the agent in patients with nephrotic syndrome.
Adolescence ; Adult ; Aged ; Albumins/*pharmacology ; Cross-Over Studies ; Diuretics/*pharmacology ; Drug Synergism ; Female ; Furosemide/*pharmacology ; Human ; Male ; Middle Age ; Nephrotic Syndrome/*drug therapy/metabolism ; Serum Albumin/analysis

Mineralocorticoids influences on acid-base homeostasis by the regulation of urine acidification. But its mechanism of acion is not well known in human. This study compared the acid-base status and the indices of urine acidification before and after mineralocorticoid administration in human, and analyzed the effect of mineralocorticoids on human acid-base homeostasis. We administered 9a-fludrocortisone in 6 chronic renal failure patients and 6 normal controls 0.5mg daily for 7 days. The results were as following: 1) After administration of 9a-fludrocortisone in patients group, serum aldosterone level changed from 120.2+/-71.0pg/mL to 44.8+/-32.2pg/mL(mean+/-SD, p< 0.05). Serum HCO- level was not changed. Urine ammonium excretion was incresed from 24.6+/-12.3 mmol/day to 43.7+/-19.0 (p<0.05), but there were no change in urine pH and urine anion gap, Serum potassium level decreased from 5.5+/-0.7mBq/L to 4.1+/-0.5mEq/L (p<0.05), and TTKG increased from 3.9 to 8.9(p<0.05). 2) After administration of 9a-fludrocortisone in control group, serum aldosterone level changed from 99.7+/-44.5pg/mL to 25.1+/-3 mL(p<0.05). Serum HCO- level was not changed. Urine ammonium excretion was incresed from 44.3+/-21.6mmoVday to 76.3+/-19.6(p<0.05), but there were no change in urine pH and urine anion gap. Serum potassium level decreased from 4.8+/-0.5mEq/L to 3.9+/-0.2mHq/L(p< 0.05), but there was no change in TTKG. 3) No patient or control showed any discomfort after 9-fludrocortisone administration, and there was no elevation in diastolic blood pressure, increase in body weight, electrolyte abnormality. In summary, after 9alpha-fludrocortisane administration, urinary ammonium excretion increased in both patients and control group, and this phenomenon occured with correction of hyperkalemia without urine pH change. This result implies urinary ammonium excretion increase by mineralocorticoid. In human increase in renal distal acidification by mineralocorticoid is due to increase in renal ammoniagenesis rather than stimulation on proton excretion.
Acid-Base Equilibrium ; Aldosterone ; Ammonium Compounds* ; Blood Pressure ; Body Weight ; Homeostasis ; Humans ; Hydrogen-Ion Concentration ; Hyperkalemia ; Kidney Failure, Chronic ; Mineralocorticoids ; Potassium* ; Protons

Alcohol can cause rhabdomyolysis by either direct toxicity or associated metabolic abnormality such as hypophosphatemia and hypokalemia. It can also predispose to or cause trauma, seizures, or coma- induced ischemic pressure necrosis. In order to investigate the clinical features of acute renal failure caused by alcohol induced rhabdomyolysis, we reviewed the medical records of the 12 patients. All patients had been drinking much amounts of alcohol for several years. All patients showed elevation of muscle enzyme such as creatine phosphokinase, lactic dehydrogenase, aspartate transaminase and blood urea nitrogen and serum creatinine. Predisposing factors of rhabdomyolysis were ischemic compression due to unconsciousness and dehydration(2 cases), and hypophosphatemia and dehydration(1 case), seizure and dehydration(1 case), and only severe dehydration(3 cases). Initial symptoms were painful swelling at lesion site(5 cases), abdominal pain(2 cases), general ache(2 cases), leg pain without swelling(1 case), dyspnea(1case), and lethargy(1 case). Seven patients developed delirium tremens during recovery stage. Eight patients showed oliguric acute renal failure and 8 patients were treated with hemodialysis. Complications were disseminated intravascular coagulation(DIC)(3 cases), compartment syndrome(2 cases), capillary leak syndrome and DIC(1 case). One of 12 patients died of disseminated intravascular coagulation and other patients showed complete recovery of renal function.
Acidosis* ; Acute Kidney Injury ; Alcohol Withdrawal Delirium ; Aspartate Aminotransferases ; Blood Urea Nitrogen ; Capillary Leak Syndrome ; Causality ; Creatine Kinase ; Creatinine ; Disseminated Intravascular Coagulation ; Drinking ; Humans ; Hypokalemia ; Hypophosphatemia ; Leg ; Medical Records ; Necrosis ; Oxidoreductases ; Renal Dialysis ; Rhabdomyolysis ; Seizures ; Unconsciousness

BACKGROUND: Sodium retention occurs in some patients taking NSAIDs (nonsteroidal anti-inflammatory drugs). Although the renal effects of NSAIDs are predominantly mediated through the inhibition of prostaglandins synthesized by cyclooxygenase-2 (COX-2), the mechanisms of sodium retention are not clear at the sodium transporter levels in the kidney. Previous studies have shown that compensatory upregulation of COX-2 is induced in renal medulla by high salt intake and that NSAID-induced sodium retention may be transitory. METHODS: To investigate whether renal sodium transporter abundances are altered by NSAID administration and whether renal sodium transporter abundances are affected by high salt intake or chronic NSAID administration, we performed an acute study treated with a single injection of diclofenac and another chronic study treated with 7 days' administration of DFU, a selective COX-2 inhibitor, using semiquantitative immunobotting from rat kidneys. Male Sprague-Dawley rats were divided into three groups in each study: controls, NSAID treatment, and high-salt intake plus NSAID treatment. The control diet contained sodium 1 mmol/200 g BW/day, and the high-salt diet 10 mmol/200 g BW/day. RESULTS: The acute study using diclofenac (100 mg/kg BW) increased the abundances of NKCC2 (by 73%) and ENaC-alpha (by 60%) in cortex and of NKCC2 (by 165%) and ENaC-alpha (by 91%) in outer medulla, in association with a significant decrease in urinary sodium excretion. The increased ENaC-alpha abundance was reversed by addition of high salt intake in both cortex and outer medulla. The chronic study using DFU (40 mg/kg/d for 7 days) showed no significant changes in distal renal sodium transporters except a decreased abundance of Na-K- ATPase alpha1-subunit (by 24%) in outer medulla. The addition of high salt intake decreased the abundances of ENaC-alpha (by 35%) and ENaC-beta (by 47 %) in outer medulla. CONCLUSION: The abundances of thick ascending limb NKCC2 and collecting duct ENaC are altered in response to NSAID administration. It is suggested that NKCC2 & ENaC are contributory to NSAID- induced sodium retention and also have a compensatory role in high salt intake and chronic NSAID administration.
Adenosine Triphosphatases ; Animals ; Anti-Inflammatory Agents, Non-Steroidal ; Cyclooxygenase 2 ; Diclofenac ; Diet ; Extremities ; Humans ; Kidney ; Male ; Prostaglandins ; Rats ; Rats, Sprague-Dawley ; Sodium* ; Up-Regulation

BACKGROUND: The antidiuretic action of oxytocin in human has been controversial. To investigate whether oxytocin directly acts on water balance in human, we evaluated the parameters of urinary concentration in response to administration of oxytocin in ten healthy male volunteers. METHODS: Oxytocin was infused intravenously at a rate of 20 mU/hour for 2.5 hours and urine was collected during the last 2 hours of oxytocin infusion. Changes in urine volume, urine osmolality, excretions of urine electrolytes and free water clearance after the administrartion of oxytocin were compared with the baseline data. RESULTS: The changes in the levels of serum electrolytes and osmolality after the administration of oxytocin were not significant compared with the baseline data. The volume of 2 hours' urine were 446+/-75 mL and 289+/-53 mL in the basal state and after the administration of oxytocin, respectively. The urine osmolality was increased significantly by the infusion of oxytocin(427+/-63 mOsm/kg) compared with that in the basal state(223+/-25 mOsm/kg)(p < 0.05). The free water clearance was 110+/-51 mL/2 hours in the basal state and decreased significantly to -57+/-51 mL/2 hours(p < 0.05). CONCLUSION: We conclude that administration of oxytocin to normal men enhances urinary concentration, evidenced by increased urinary osmolality and decreased free water clearance. In human, oxytocin may play an important role in the regulation of renal water excretion as an antidiuretic hormone.
Electrolytes ; Humans ; Male ; Osmolar Concentration ; Oxytocin* ; Volunteers ; Water

Antidiuretic action of oxytocin is confirmed by in vitro study using with rat IMCD. Vasopressin is elevated in edematous disorders and may play a pathogenetic role in the formation of edema. If oxytocin plays a sirnilar role to vasopressin in water disturbances in human, oxytocin may change as the same way as vasopressin. To verify a role of oxytocin in the regulation of water balance in human, we measured plasma and urine oxytocin with vasopressin by radioimmunoassay in thirteen patients with generalized edema (8 nephrotic syndrome, 3 liver cirrhosis, 2 acute renal failure) before and after control of edema. And they were compared them with those of seven normal controls. Plasma oxytocin level correlated with plasma vasopressin level (r=0.543: P<0.05) and urinary oxytocin level correlated linearly with urinary vaso-pressin (r=0.983, P<0.01). After control of edema, body weight of patients decreased from 65+/- 2 to 58+/-2kg and fractional excretion of sodium decreased from 3.3+/-1.1 to 1.2+/-0.696 (P<0.05). There were no significant changes in serum and urine Na, osmolality, free water clearance, plasma renin activity, aldosterone and norepinephrine. In conclusion, oxytocin was elevated in edematous disorders, and may participate in formation of edema similar to vasopressin.
Aldosterone ; Animals ; Body Weight ; Edema ; Humans ; Liver Cirrhosis ; Nephrotic Syndrome ; Norepinephrine ; Osmolar Concentration ; Oxytocin* ; Plasma ; Radioimmunoassay ; Rats ; Renin ; Sodium ; Vasopressins* ; Water*

Hemodynamic factors play an important role in the development and/or progression of diabetic nephropathy. We hypothesized that renal sodium transporter dysregulation might contribute to the hemodynamic alterations in diabetic nephropathy. Otsuka Long Evans Tokushima Fatty (OLETF) rats were used as an animal model for type 2 diabetes. Long Evans Tokushima (LETO) rats were used as controls. Renal sodium transporter regulation was investigated by semiquantitative immunoblotting and immunohistochemistry of the kidneys of 40-week-old animals. The mean serum glucose level in OLETF rats was increased to 235+/-25 mg/dL at 25 weeks, and the hyperglycemia continued up to the end of 40 weeks. Urine protein/ creatinine ratios were 10 times higher in OLETF rats than in LETO rats. At 40th week, the abundance of the epithelial sodium channel (ENaC) beta-subunit was increased in OLETF rats, but the abundance of the ENaC gamma-subunit was decreased. No significant differences were observed in the ENaC alpha-subunit or other major sodium transporters. Immunohistochemistry for the ENaC beta-subunit showed increased immunoreactivity in OLETF rats, whereas the ENaC gamma-subunit showed reduced immunoreactivity in these rats. In OLETF rats, ENaC beta-subunit upregulation and ENaC gamma-subunit downregulation after the development of diabetic nephropathy may reflect an abnormal sodium balance.
Animals ; Blood Glucose/analysis ; Diabetes Mellitus, Type 2/*metabolism ; *Disease Models, Animal ; Epithelial Sodium Channel/*analysis ; Hypertension/complications ; Immunoblotting ; Immunohistochemistry ; Kidney/*metabolism ; Male ; Rats ; Sodium/*metabolism ; Sodium-Hydrogen Antiporter/genetics ; Sodium-Potassium-Chloride Symporters/genetics