Effect of acute metabolic acidemia on renal electrolyte transport in man

Primary Distal Renal Tubular Acidosis: Toward an Optimal Correction of Metabolic Acidosis

The term classic, type 1 renal tubular acidosis or primary distal renal tubular acidosis is used to designate patients with impaired ability to excrete acid normally in the urine as a result of tubular transport defects involving type A intercalated cells in the collecting duct. The clinical phenotype is largely characterized by the complications of chronic metabolic acidosis (MA): stunted growth, bone abnormalities, and nephrocalcinosis and nephrolithiasis that develop as the consequence of hypercalciuria and hypocitraturia. All these manifestations are preventable with early and sustained correction of MA with alkali therapy. The optimal target for plasma bicarbonate should be as close as possible to the range considered normal by current standards (between 23 and 28 mEq/L.). Most of the benefits of alkali therapy are tangible early in the course of the disease in childhood, but life-long treatment is required to prevent the vast array of complications attributable to chronic MA.

Persistent changes in calcium-regulating hormones and bone turnover markers in living kidney donors more than 20 years after donation

In a previous study, we observed decreased 1,25-dihydroxyvitamin D levels, secondary hyperparathyroidism, and increased bone turnover markers in living kidney donors (LKDs) at 3 months and 36 months after kidney donation. In our recent survey-based study, we found no increased risk of fractures of all types but observed significantly more vertebral fractures in LKDs compared with matched controls. To elucidate the long-term effects of kidney donation on bone health, we recruited 139 LKDs and 139 age and sex matched controls from the survey-based participants for further mechanistic analyses. Specifically, we assessed whether LKDs had persistent abnormalities in calcium- and phosphorus-regulating hormones and related factors, in bone formation and resorption markers, and in density and microstructure of bone compared with controls. We measured serum markers, bone mineral density (BMD), bone microstructure and strength (via high-resolution peripheral quantitative computed tomography and micro-finite element analysis [HRpQCT]), and advanced glycation end-products in donors and controls. LKDs had decreased 1,25-dihydroxyvitamin D concentrations (donors mean 33.89 pg/mL vs. controls 38.79 pg/mL, percent difference = -12.6%; P < .001), increases in both parathyroid hormone (when corrected for ionized calcium; donors mean 52.98 pg/mL vs. controls 46.89 pg/mL,% difference 13%; P = .03) and ionized calcium levels (donors mean 5.13 mg/dL vs. controls 5.04 mg/dL; P < .001), and increases in several bone resorption and formation markers versus controls. LKDs and controls had similar measures of BMD; however, HRpQCT suggested that LKDs have a statistically insignificant tendency toward thinner cortical bone and lower failure loads as measured by micro-finite element analysis. Our findings suggest that changes in the hormonal mileu after kidney donation and the long-term cumulative effects of these changes on bone health persist for decades after kidney donation and may explain later-life increased rates of vertebral fractures.

Autosomal dominant distal renal tubular acidosis in two pediatric patients with mutations in the SLC4A1 gene. Can the maximum urinary pCO2 test be normal?

Primary distal renal tubular acidosis (dRTA) is a rare tubulopathy characterised by the presence of hyperchloremic metabolic acidosis. It is caused by the existence of a defect in the function of the H+ -ATPase located on the luminal side of the α-intercalated cells or the Cl - HCO3- (AE1) anion exchanger located on the basolateral side. Patients do not acidify the urine after acid overload (NH4Cl) or after stimulating H+ secretion by obtaining a high intratubular concentration of an anion such as chlorine (pH is measured) or HCO3- (urinary pCO2 is measured). We present a family with autosomal dominant dRTA produced by a heterozygous mutation in the SLC4A1 gene in which the two paediatric members showed a test of normal maximum urinary pCO2. Our hypothesis is that since the H + -ATPase is intact, at least initially, the stimulation induced by intratubular electronegativity to secrete H + could be effective, which would allow the maximum urinary pCO2 to be paradoxically normal, which could explain the onset, moderate presentation of symptoms and late diagnosis in patients with this mutation. This is the first documented case of a dominant dRTA in Mexico.

Effects of Low Dietary Cation and Anion Difference on Blood Gas, Renal Electrolyte, and Acid Excretions in Goats in Tropical Conditions

Goats can suffer from intermittent heat stress in high ambient temperature (HTa) conditions, which causes sporadic respiratory hypocapnia. Obstructive urolithiasis is a common urological problem in goats. Sandy uroliths can be partially relieved by urine acidification with short-term ammonium chloride (NH4Cl) treatment. However, the outcome of urine acidification and the physiological responses to short-term NH4Cl supplementation under respiratory hypocapnia of HTa have rarely been reported. The present study investigated the effect of NH4Cl supplementation that produced a low dietary cation-anion different (l-DCAD) diet on acid-base balance and renal function under HTa conditions. The first experiment investigated the physiological responses to natural HTa to prove whether the peak HTa during the afternoon could induce HTa responses without a change in the plasma cortisol. The partial pressure of CO2 also tended to decrease during the afternoon. The second experiment examined the short-term effect of l-DCAD under HTa conditions. Although the blood pH was within the normal range, there was a clear acid-base response in the direction of metabolic acidosis. The major responses in renal function were an increase in tubular function and acid excretion. With a comparable level of creatinine clearance, the fractional excretions (FE) of chloride and calcium increased, and the FE of potassium decreased. Acid excretion increased significantly in the l-DCAD group. We conclude that under HTa conditions, the tubular excretion of electrolytes and acids was the major response to acid loading without changing the filtration rate. The l-DCAD formulation can be used to acidify urine effectively.

A familial case of pseudohypoaldosteronism type II (PHA2) with a novel mutation (D564N) in the acidic motif in WNK4

Background

There have been still few case reports of pseudohypoaldosteronism type II (PHA2), also known as Gordon's syndrome, genetically diagnosed, and this is the first report of familial PHA2 case in Japan with a novel D564N mutation in WNK4.

Methods

A 29‐year‐old woman was admitted to our hospital due to hyperkalemia (serum potassium: 6.4 mmol/L). She had mild hypertension (135/91 mm Hg), a bicarbonate level at the lower limit of the normal range (HCO₃: 22 mmol/L) with a normal anion gap, low plasma renin activity (0.2 ng ml^‐1 hr^‐1), and high urinary calcium excretion (505.4 mg/g Cre). A hereditary condition was suspected because her mother also had the same symptoms. We performed a comprehensive genetic analysis for major inherited kidney diseases with next‐generation sequencing including the genes responsible for PHA2 (WNK1, WNK4, KLHL3, and CUL3).

Results

Genetic analysis revealed that the patient and her mother had a novel missense mutation (D564N) in the acidic motif in WNK4, which leads to the diagnosis of PHA2. Administration of trichlormethiazide (1 mg/day) effectively ameliorated her blood pressure (114/69 mm Hg), plasma bicarbonate (25 mmol/L), serum potassium (4.3 mmol/L), and urinary calcium excretion (27.2 mg/g Cre).

Conclusion

We report the first Japanese familial case of PHA2 with WNK4 mutation. D564N mutation in WNK4 is a novel genetic cause of PHA2 with a relatively mild phenotype.

Saline versus Plasma-Lyte A in initial resuscitation of trauma patients: a randomized trial

OBJECTIVE

We sought to compare resuscitation with 0.9% NaCl versus Plasma-Lyte A, a calcium-free balanced crystalloid solution, hypothesizing that Plasma-Lyte A would better correct the base deficit 24 hours after injury.

BACKGROUND

Sodium chloride (0.9%) (0.9% NaCl), though often used for resuscitation of trauma patients, may exacerbate the metabolic acidosis that occurs with injury, and this acidosis may have detrimental clinical effects.

METHODS

We conducted a randomized, double-blind, parallel-group trial (NCT01270854) of adult trauma patients requiring blood transfusion, intubation, or operation within 60 minutes of arrival at the University of California Davis Medical Center. Based on a computer-generated, blocked sequence, subjects received either 0.9% NaCl or Plasma-Lyte A for resuscitation during the first 24 hours after injury. The primary outcome was mean change in base excess from 0 to 24 hours. Secondary outcomes included 24-hour arterial pH, serum electrolytes, fluid balance, resource utilization, and in-hospital mortality.

RESULTS

Of 46 evaluable subjects (among 65 randomized), 43% had penetrating injuries, injury severity score was 23 ± 16, 20% had admission systolic blood pressure less than 90 mm Hg, and 78% required an operation within 60 minutes of arrival. The baseline pH was 7.27 ± 0.11 and base excess -5.9 ± 5.0 mmol/L. The mean improvement in base excess from 0 to 24 hours was significantly greater with Plasma-Lyte A than with 0.9% NaCl {7.5 ± 4.7 vs 4.4 ± 3.9 mmol/L; difference: 3.1 [95% confidence interval (CI): 0.5-5.6]}. At 24 hours, arterial pH was greater [7.41 ± 0.06 vs 7.37 ± 0.07; difference: 0.05 (95% CI: 0.01-0.09)] and serum chloride was lower [104 ± 4 vs 111 ± 8 mEq/L; difference: -7 (95% CI: -10 to -3)] with Plasma-Lyte A than with 0.9% NaCl. Volumes of study fluid administered, 24-hour urine output, measures of resource utilization, and mortality did not significantly differ between the 2 arms.

CONCLUSIONS

Compared with 0.9% NaCl, resuscitation of trauma patients with Plasma-Lyte A resulted in improved acid-base status and less hyperchloremia at 24 hours postinjury. Further studies are warranted to evaluate whether resuscitation with Plasma-Lyte A improves clinical outcomes.

Ammonium chloride metabolic acidosis and the activity of renin-angiotensin-aldosterone system in children

The present study was undertaken to assess the effects of acute metabolic acidosis on the activity of the renin-angiotensin-aldosterone system in 12 children with a mean age of 8.9 years who underwent NH4Cl loading test. Ammonium chloride was given in a dose of 0.15 g/kg per day for 3 consecutive days to evaluate renal acidification. Prior to and following NH4Cl administration blood acid-base parameters, plasma and urine electrolytes, creatinine and aldosterone concentrations as well as plasma renin activity (PRA), urine flow rate and net H+ excretion were measured. Ammonium chloride administration significantly depressed blood pH (P less than 0.05), bicarbonate (P less than 0.01) and base excess (P less than 0.01) and resulted in a slight, but significant elevation of plasma potassium concentration (P less than 0.05). Furthermore, NH4Cl ingestion induced a marked increase in urine flow rate (P less than 0.01) and urinary sodium, potassium and chloride excretion (P less than 0.01). In response to NH4Cl metabolic acidosis, PRA doubled (4.72 +/- 1.18 vs 8.13 +/- 1.02 ng/ml per hour, P less than or equal to 0.05) and there was a nearly four-fold increase in plasma aldosterone level (0.49 +/- 0.12 vs 1.52 +/- 0.24 ng/ml, P less than 0.01) and in urinary aldosterone excretion (19.2 +/- 4.3 vs 71.8 +/- 13.8 micrograms/day, P less than 0.01). The elevated aldosterone production observed in this study is assumed to be mediated by the combined effect of sodium and water diuresis-related increased PRA, hyperkalaemia and the direct stimulation of adrenal steroidogenesis by metabolic acidosis.

Effect of ammonium-chloride-induced metabolic acidosis on renal electrolyte handling in human neonates

The present study was undertaken to determine the relative contribution of altered glomerular and tubular functions to the metabolic-acidosis-induced increase of renal electrolyte excretion in healthy preterm and full-term neonates and in older infants. Studies were performed in 10 premature infants (mean birth weight 1618 g, gestational age 30.8 weeks) weekly for 6 consecutive weeks, in 11 full-term neonates (mean birth weight 3085 g, gestational age 38.6 weeks) on the 7th day of life and in 25 older control infants (mean age 6.5 months, body weight 6802 g), before and after NH4Cl loading. Blood acid-base parameters, plasma and urine electrolyte and creatinine concentrations were measured, endogenous creatinine clearance and fractional electrolyte excretion (FE) calculated. It was demonstrated that the significant reduction in blood pH and total CO2 content induced by NH4Cl administration was associated with significant increases in glomerular filtration rate (GFR), urine flow rate, FENa and FECl, in each group studied, irrespective of maturity, postnatal age or pre load values. FEK also tended to increase, but the change reached statistical significance only in older infants and in premature babies during the 1st, 2nd and 5th week of post-natal life. FECa and FEPO4 increased slightly in preterm and full-term newborns and became significant in older infants. Prior to NH4Cl administration, FECa correlated positively with FENa in each group. NH4Cl metabolic acidosis, however, dissociated FECa from FENa in the full-term newborns and older infants but not in the preterm neonates.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute effect of ethanol on renal electrolyte excretion in rats

The purpose of this study was to investigate the renal handling of sodium and potassium in rats during an acute ethanol (ETOH) administration and to relate any observed changes to alterations in renin-aldosterone secretion. Eight male Wistar rats, 7 to 8 weeks of age, were injected intraperitoneally (IP) with 1.0 g/kg body wt. ETOH (15% v/v, 95% ETOH in saline, pH 6.98, osmolality 284 mOsm/kg). Blood ETOH levels were 159 +/- 16 (Mean +/- SEM) and 120 +/- 12 mg/dl, 10 and 30 min after the ETOH injection respectively (p less than 0.05). Control animals were given either an equal volume (1.77 ml/100 g body wt.) of 0.9% saline (n = 6) or 5% dextrose solution (n = 4) with similar pH and osmolality. Following ETOH administration blood pH, urine pH, plasma bicarbonate (HCO3) concentration declined significantly (p less than 0.01) while glomerular filtration rate (GFR) and hematocrit (Hct) remained unchanged (p = 0.1). Mean fractional sodium excretion (FENa), fractional potassium excretion (FEK), and osmolar clearance (Cosm) fell significantly despite an increase in plasma sodium (p less than 0.01), potassium (p less than 0.05) and osmolality concentrations (p less than 0.05). There was no significant change in plasma aldosterone concentration (PA) or plasma renin activity (PRA) following the ETOH administration. No difference in GFR, FENa, FEK, Cosm, blood pH, urine pH, plasma electrolytes, PA, or PRA was observed following the saline or dextrose injections. In conclusion, acute ETOH administration in rats alters renal sodium and potassium excretion independent of changes in GFR, PA, PRA or plasma volume as reflected by Hct.

Effect of hyperketonemia on renal ammonia excretion in man

The effect of DL-sodium beta-hydroxybutyrate (Na BOHB) on urinary ammonia excretion was studied in seven chronically acidemic human subjects. Metabolic acidosis was induced by the ingestion of 0.1 g/kg body weight of ammonium chloride for three days. On the morning of day 4, baseline blood and urine samples were collected during three 30-minute periods. Na BOHB (1 mmol/kg, pH = 7.4) was then infused over 20 minutes, and this was followed by a continuous infusion at the rate of 10 mumol/kg min for 160 minutes. Urinary ammonia excretion decreased by 35% (P less than 0.001) while urine pH rose slightly from 5.49 to 5.82 (P less than 0.002). Venous pH increased from 7.31 to 7.38 (P less than 0.005) and bicarbonate concentration from 19 to 25 mEq/L (P less than 0.002). Four subjects were restudied with an infusion of Na beta-OHB (pH adjusted to 4.4 with the addition of HCI). Venous pH and bicarbonate concentration did not change significantly while urine pH decreased from 5.25 to 4.90 (P less than 0.001). Urinary ammonia excretion fell by 34% (P less than 0.01) despite the decline in urine pH and the absence of change in blood pH and bicarbonate concentration. Three subjects were restudied with sodium bicarbonate (0.52 to 0.85 mEq/min) infusion. Despite similar increases in blood pH and plasma bicarbonate concentration as observed with Na beta-OHB at pH = 7.4, urinary ammonia excretion did not fall significantly. In an attempt to simulate the change in redox potential and NAD+ to NADH ratio that occurred during the metabolism of beta-hydroxybutyrate to acetoacetate, sodium lactate was given to four subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of induced total-body hyperthermia on phosphorus metabolism in humans

The effects of total-body hyperthermia on phosphorus homeostasis are controversial. To evaluate the problem, 10 clearance studies were performed in seven patients undergoing total-body hyperthermia as an adjunct to the treatment of solid malignant tumors. Total-body hyperthermia was associated with significant reduction in plasma phosphorus concentration from a baseline value of 3.51 +/- 0.18 to 0.6 +/- 0.1 mg/dl (p less than 0.001), returning to baseline following cessation of total-body hyperthermia. The clearance of phosphorus increased from 15.2 +/- 2.5 to 26.1 +/- 3.1 ml per minute (p less than 0.01), and the fractional excretion of phosphorus increased from 11.37 +/- 2.2 to 47.68 +/- 9.7 percent (p less than 0.01). The reduction in plasma phosphorus during total-body hyperthermia was also associated with a significant reduction in the renal threshold phosphorus concentration from 3.17 +/- 0.16 to 0.38 +/- 0.08 (p less than 0.001). The changes in phosphorus homeostasis during total-body hyperthermia were independent of changes in circulating parathyroid hormone level, urinary cyclic AMP excretion, and arterial carbon dioxide tension.

Effects of High Intake of Dietary Animal Protein on Mineral Metabolism and Urinary Supersaturation of Calcium Oxalate in Renal Stone Formers

The metabolic effects of a high protein diet (HPD) were studied in eight patients with idiopathic recurrent calcium oxalate stones. On the HPD there was a 35% increase in urinary calcium concomitant with increased excretion of cyclic AMP and hydroxyproline. These findings point to an enhanced resorption of bone, possibly secondary to increased renal loss of calcium. The urinary citrate decreased by 25% along with reduced serum standard bicarbonate and urinary pH. The high formation of acid metabolites might also have adverse effects on calcium balance and bone. Urinary oxalate excretion was not affected nor were there any significant changes in the calculated urinary supersaturation of calcium oxalate, if changes in urinary citrate, pH, sulphate, sodium, phosphate and volume were also considered. This study suggests that the possible negative influence on the propensity to form renal stones of a diet rich in animal protein is probably due to reduced urinary inhibitory activity.

The effect of insulin on renal sodium metabolism. A review with clinical implications

Data are discussed which demonstrate that insulin plays an important role in sodium metabolism. The primary action of insulin on sodium balance is exerted on the kidney. Increases in plasma insulin concentration within the physiological range stimulate sodium reabsorption by the distal nephron segments and this effect is independent of changes in circulating metabolites or other hormones. Several clinical situations are reviewed: sodium wasting in poorly controlled diabetics, natriuresis of starvation, anti-natriuresis of refeeding and hypertension of obesity, in which insulin-mediated changes in sodium balance have been shown to play an important pathophysiological role.

Epinephrine and potassium homeostasis

The effect of epinephrine on potassium metabolism was examined in six subjects. Each subject participated in four studies as follows: (1) potassium chloride infusion (0.75 mEq/kg, i.v.) given over 2 hours, (2) epinephrine (0.05 micrograms/kg.min) plus potassium chloride, (3) propranolol (1.43 micrograms/kg.min) plus epinephrine plus potassium chloride, and (4) propranolol plus potassium chloride. The epinephrine infusion with potassium chloride led to a marked improvement in potassium tolerance, which was due to a greater than twofold increase in the extrarenal disposal of potassium (P less than 0.001). The enhancing effect of epinephrine on extrarenal potassium uptake was completely reversed with the beta-blocking agent propranolol. When propranolol alone was infused with potassium chloride, a significant decrease in the extrarenal disposal of potassium was observed. When potassium chloride was infused alone, 47% of the administered potassium load was excreted in the urine. Epinephrine infusion with potassium chloride markedly inhibited the urinary excretion of potassium (UkV) to rates that were actually below the basal potassium excretion rate (P less than 0.001). Propranolol almost completely reversed this effect of epinephrine on UkV, and when propranolol was infused alone, an enhancement in UkV (P less than 0.005) was observed. Insulin adds only a minor contribution to the enhancing effect of epinephrine on extrarenal potassium disposal and dose not contribute at all to the inhibitory effect of epinephrine on renal potassium excretion. These results demonstrate that epinephrine ameliorates the rise in plasma potassium concentration following potassium chloride infusion. Because none of the infused potassium was excreted during the 4-hour study period, the improvement in potassium tolerance must result from an enhancement in extrarenal potassium disposal. The ability of propranolol to reverse both the extrarenal and renal effects indicates that the action of epinephrine is mediated via stimulation of the beta receptor.

Effect of mineralocorticoid replacement therapy on renal acid-base homeostasis in adrenalectomized patients

Chronic balance studies were performed in six adrenalectomized patients to investigate the renal and systemic acid-base consequences of mineralocorticoid deficiency in the absence of either glucocorticoid deficiency or parenchymal renal disease. Constant glucocorticoid replacement was provided with dexamethasone, 750 to 875 micrograms/day, administered orally. Creatinine clearance averaged 98 +/- 8 ml/min/1.73 m2. Following a control period, mineralocorticoid replacement with fludrocortisone (100 to 200 micrograms/day) was either discontinued (N = 3) or initiated (N = 2). In an additional patient, mineralocorticoid replacement was initiated and sustained (5 days) by continuous i.v. infusion of aldosterone, at a dose approximating the normal secretion rate (120 micrograms/day). Net acid excretion (NAE) and plasma total carbon dioxide decreased in each patient in whom mineralocorticoid was discontinued and increased in each patient in whom mineralocorticoid was initiated. The cumulative change in NAE (sigma delta NAE) independent of direction averaged 66 +/- 20 mEq (P less than 0.05) by the fifth experimental day in the six patients, and the corresponding change in plasma total CO2 averaged 1.2 +/- 0.3 mmoles/liter (P less than 0.02). The magnitude of sigma delta NAE correlated with the basal rate of NAE (r = 0.87, P less than 0.05), which averaged 0.9 +/- 0.1 mEq/kg body wt per day. The change in plasma total CO2 correlated with sigma delta NAE (r = 0.83, P less than 0.05). The changes in NAE correlated positively with the corresponding changes in sodium balance and negatively with the corresponding changes in potassium balance. These findings provide the first evidence that renal acidification is under tonic stimulation by mineralocorticoid at levels not exceeding those in normal subjects ingesting acid-producing diets of normal sodium and potassium content. The extent to which the tonic stimulation of renal acidification is mediated by a direct effect of mineralocorticoid on renal hydrogen ion transport or by an indirect effect dependent on altered renal sodium and/or potassium transport requires further investigation. The findings implicate mineralocorticoid deficiency as a significant renal acidosis-producing condition not dependent on the presence of renal disease or glucocorticoid deficiency, and potentially amplified when endogenous acid production is increased by diet or disease.

Hypophosphatemia and glucose intolerance: evidence for tissue insensitivity to insulin

Although hypophosphatemia is commonly present in diabetics, little is known about its isolated effects on glucose and insulin metabolism. We therefore investigated glucose metabolism in six nondiabetic subjects with chronic hypophosphatemia. When glucose was infused to maintain a constant hyperglycemic level (125 mg per deciliter [6.9 mmol per liter] above basal levels), the glucose infusion rate was 36 per cent less in the hypophosphatemic group than in controls (4.90 +/- 0.34 mg per kilogram of body weight per minute vs. 7.64 +/- 0.37, P < 0.001), although responses to endogenous insulin were similar. When exogenous insulin was infused at a constant rate to maintain an insulin level about 100 microU per milliliter (718 pmol per liter) above basal levels and glucose was infused as necessary to maintain fasting glucose levels, the infusion rate of glucose was 43 per cent lower in the hypophosphatemic group than in controls (3.80 +/- 0.58 mg per kilogram per minute vs. 6.70 +/- 0.33, P < 0.001), although the clearance rate of insulin was similar in both groups. These results indicate that hypophosphatemia is associated with impaired glucose metabolism in both the hyperglycemic and euglycemic states, and that this associated primarily reflects decreased tissue sensitivity to insulin. (N Engl J Med. 1980; 303; 1259-63.).