Trimetazidine Protects from Mercury-Induced Kidney Injury

INTRODUCTION

The presence of mercury in the environment is a worldwide concern. Inorganic mercury is present in industrial materials, is employed in medical devices, is widely used in batteries, is a component of fluorescent light bulbs, and it has been associated with human poisoning in gold mining areas. The nephrotoxicity induced by inorganic mercury is a relevant health problem mainly in developing countries. The primary mechanism of mercury toxicity is oxidative stress. Trimetazidine (TMZ) is an anti-ischemic drug, which inhibits cellular oxidative stress, eliminates oxygen-free radicals, and improves lipid metabolism. The aim of this study was to evaluate whether the administration of TMZ protects against mercuric chloride (HgCl2) kidney damage.

METHODS

Adult male Wistar rats received only HgCl2 (4 mg/kg bw, sc) (Hg group, n = 5) or TMZ (3 mg/kg bw, ip) 30 min before HgCl2 administration (4 mg/kg bw, sc) (TMZHg group, n = 7). Simultaneously, a control group of rats (n = 4) was studied. After 4 days of HgCl2 injection, urinary flow, urea and creatinine (Cr) plasma levels, Cr clearance, urinary glucose, and sodium-dicarboxylate cotransporter 1 (NaDC1) in urine were determined. Lipid peroxidation (MDA) and glutathione (GSH) levels were measured in kidney homogenates.

RESULTS

Rats only treated with HgCl2 showed an increase in urea and Cr plasma levels, urinary flow, fractional excretion of water, glucosuria, and NaDC1 urinary excretion as compared with the control group and a decrease in Cr clearance. TMZHg group showed a decrease in urea and Cr plasma levels, urinary flow, fractional excretion of water, glucosuria, NaDC1 urinary excretion, and an increase in Cr clearance when compared to the Hg group. Moreover, MDA and GSH levels observed in Hg groups were decreased and increased, respectively, by TMZ pretreatment.

CONCLUSION

TMZ exerted a renoprotective action against HgCl2-induced renal injury, which might be mediated by the reduction of oxidative stress. Considering the absence of toxicity of TMZ, its clinical application against oxidative damage due to HgCl2-induced renal injury should be considered. The fact that TMZ is commercially available should simplify and accelerate the translation of the present data "from bench to bedside." In this context, TMZ become an interesting new example of drug repurposing.

Urine chloride self-measurement to monitor sodium chloride intake in patients with chronic kidney disease

Background Excessive sodium intake is a risk factor for hypertension, cardiovascular disease and the risk for kidney failure in chronic kidney disease (CKD) patients. Methods We tested the diagnostic performance and the feasibility of an inexpensive method based on urine chloride strips for self-monitoring sodium intake in a series of 72 CKD patients. Results Twenty-four hour urinary chloride as measured by the reactive strips and 24 h urinary sodium were interrelated (r=0.59, p<0.001). Forty-nine out of 72 patients (78%) had a 24 h urinary sodium >100 mmol/24 h, i.e. the upper limit recommended by current CKD guidelines. The strip method had 75.5% sensitivity and 82.6% specificity to correctly classify patients with urine sodium >100 mmol/24 h. The positive and the negative predictive values were 90.2% and 61.3%, respectively. The overall accuracy (ROC curve analysis) of urine chloride self-measurement for the >100 mmol/24 h sodium threshold was 87% (95% CI: 77%-97%). The large majority of patients (97%) perceived the test as useful to help compliance with the prescribed dietary sodium and considered the test as simple and of immediate application (58%) or feasible but requiring attention (39%). Conclusions A simple and inexpensive test for urine chloride measurement has a fairly good performance for the diagnosis of excessive sodium intake. The test is feasible and it is perceived by CKD patients as helpful for enhancing compliance to the dietary sodium recommendations. The usefulness of this test for improving hypertension control in CKD patients will be tested in a clinical trial (Clinicaltrials.gov RF-2010-2314890).

Sodium and Salt Consumption in Latin America and the Caribbean: A Systematic-Review and Meta-Analysis of Population-Based Studies and Surveys

Sodium/salt consumption is a risk factor for cardiovascular diseases. Although global targets to reduce salt intake have been established, current levels and trends of sodium consumption in Latin America and the Caribbean (LAC) are unknown. We conducted a systematic review and meta-analysis of population-based studies in which sodium consumption was analyzed based on urine samples (24 h samples or otherwise). The search was conducted in Medline, Embase, Global Health, Scopus and LILACS. From 2350 results, 53 were studied in detail, of which 15 reports were included, providing evidence for 18 studies. Most studies were from Brazil (7/18) and six collected 24 h urine samples. In the random effects meta-analysis, 12 studies (29,875 people) were analyzed since 2010. The pooled mean 24 h estimated sodium consumption was 4.13 g/day (10.49 g/day of salt). When only national surveys were analyzed, the pooled mean was 3.43 g/day (8.71 g/day of salt); when only community studies were analyzed the pooled mean was 4.39 g/day (11.15 g/day of salt). Studies had low risk of bias. The estimated 24 h sodium consumption is more than twice the World Health Organization recommendations since 2010. Regional organizations and governments should strengthen policies and interventions to measure and reduce sodium consumption in LAC.

The Science of Salt: A regularly updated systematic review of the implementation of salt reduction interventions (September 2016-February 2017)

This periodic review aims to identify, summarize, and appraise studies relating to the implementation of salt reduction strategies that were published between September 2016 and February 2017. A total of 41 studies were included as relevant to the design, assessment, and implementation of salt reduction strategies, and a detailed appraisal was conducted on the seven studies that evaluated the impact of salt reduction strategies. Of these, three were national studies or included large populations and four were conducted in communities with small participant sample sizes. Each study used a different strategy for reducing salt intake varying from category-specific sodium targets for packaged food to use of a low-sodium salt substitute to behavior change interventions. Four studies found statistically significant decreases in dietary salt intake and one study showed statistically significant decreases in mean sodium density of packaged food products. Four of the seven studies used either spot or 24-hour urine samples to measure dietary salt intake and five were conducted in East or Southeast Asia-two of which were in low- and middle-income countries. Study quality varied among the seven studies and all except one had one or more risks related to bias.

The SONG (Salt intake and OrigiN from General foods) Study - A Large-scale Survey of the Eating Habits and Dietary Salt Intake in the Working-age Population

Objective Dietary salt reduction is important for the prevention and treatment of lifestyle-related diseases, including hypertension. Thus, in order to follow a strict low-salt diet, it is necessary to assess one's salt intake and to become aware of the importance of salt reduction. Methods More than 2,000 employees of a company, who received a periodic health checkup, participated in the present study. They assessed their day-to-day diet-related lifestyle, using the Salt Check Sheet, and we analyzed the correlations among the Salt Check Sheet scores, the daily salt intake (as estimated by a spot urine sample), and the results of the periodic health checkup. Results In the overall survey population, we only found a weak correlation between the salt check scores and the salt intake. In a subgroup analysis, significant correlations between these two variables were observed among untreated hypertensive participants, but not among treated hypertensive participants. We examined the association between 13 individual questionnaire items and the estimated daily salt intake using a multivariate linear regression model and found that only 5 of the 13 questionnaire items were correlated with the daily salt intake. Conclusion We found that a Salt Check Sheet composed of the 5 items that showed a strong correlation with the salt intake might be more useful for periodic health checks of the working-age population.

Mean Dietary Salt Intake in Urban and Rural Areas in India: A Population Survey of 1395 Persons

BACKGROUND

The scientific evidence base in support of population-wide salt reduction is strong, but current high-quality data about salt intake levels in India are mostly absent. This project sought to estimate daily salt consumption levels in selected communities of Delhi and Haryana in north India and Andhra Pradesh in south India.

METHODS AND RESULTS

In this study, 24-hour urine samples were collected using an age- and sex-stratified sampling strategy in rural, urban, and slum areas. Salt intake estimates were made for the overall population of each region and for major subgroups by weighting the survey data for the populations of Delhi and Haryana, and Andhra Pradesh. Complete 24-hour urine samples were available for 637 participants from Delhi and Haryana and 758 from Andhra Pradesh (65% and 68% response rates, respectively). Weighted mean population 24-hour urine excretion of salt was 8.59 g/day (95% CI 7.68-9.51) in Delhi and Haryana and 9.46 g/day (95% CI 9.06-9.85) in Andhra Pradesh (P=0.097). Estimates inflated to account for the minimum likely nonurinary losses of sodium provided corresponding estimates of daily salt intake of 9.45 g/day (95% CI 8.45-10.46) and 10.41 g/day (95% CI 9.97-10.84), respectively.

CONCLUSIONS

Salt consumption in India is high, with mean population intake well above the World Health Organization recommended maximum of 5 g/day. A national salt reduction program would likely avert much premature death and disability.

Seasonal Variation in the Daily Urinary Sodium Excretion in Outpatients from the Morioka Region of Northern Japan

Objective Although the daily urinary sodium excretion (UNaV) is considered to provide the most reliable estimate of the daily sodium intake, it may be affected by salt loss due to sweating in summer. However, the seasonal variation in the daily UNaV associated with a normal lifestyle is unknown. Methods This study was performed in 348 outpatients from the Morioka region during three seasons: summer (summer 1), winter, and the following summer (summer 2). The daily UNaV (g salt/day) was estimated by the second morning urine method three times during each season. Seasonal variation was defined as a significant trend across the three seasons together with a significant difference between winter and both summers. Results In women, the daily UNaV was higher in winter (11.8±3.0 g salt/day) than in summer 1 (11.2±2.9 g salt/day) or summer 2 (11.0±2.9 g salt/day). In contrast, there was no marked seasonal variation in men. An analysis stratified by age (4 quartiles) identified seasonal variation in the older 2 quartiles of women (aged ≥68 years). In these women, the mean seasonal difference in the daily UNaV was 0.9 g of salt/day for both winter vs. summer 1 and winter vs. summer 2, while it was 0.1-0.8 g of salt/day in the other groups. Conclusion Seasonal variation in the daily UNaV only occurred in older female patients and was relatively small. This is evidence for restricting salt intake throughout the year and should reassure patients who are anxious about salt loss due to sweating in summer.

Salt-sparing diuretic action of a water-soluble urea analog inhibitor of urea transporters UT-A and UT-B in rats

Inhibitors of kidney urea transporter (UT) proteins have potential use as salt-sparing diuretics ('urearetics') with a different mechanism of action than diuretics that target salt transporters. To study UT inhibition in rats, we screened about 10,000 drugs, natural products and urea analogs for inhibition of rat UT-A1. Drug and natural product screening found nicotine, sanguinarine and an indolcarbonylchromenone with IC50 of 10-20 μM. Urea analog screening found methylacetamide and dimethylthiourea (DMTU). DMTU fully and reversibly inhibited rat UT-A1 and UT-B by a noncompetitive mechanism with IC50 of 2-3 mM. Homology modeling and docking computations suggested DMTU binding sites on rat UT-A1. Following a single intraperitoneal injection of 500 mg/kg DMTU, peak plasma concentration was 9 mM with t1/2 of about 10 h, and a urine concentration of 20-40 mM. Rats chronically treated with DMTU had a sustained, reversible reduction in urine osmolality from 1800 to 600 mOsm, a 3-fold increase in urine output, and mild hypokalemia. DMTU did not impair urinary concentrating function in rats on a low protein diet. Compared to furosemide-treated rats, the DMTU-treated rats had greater diuresis and reduced urinary salt loss. In a model of syndrome of inappropriate antidiuretic hormone secretion, DMTU treatment prevented hyponatremia and water retention produced by water-loading in dDAVP-treated rats. Thus, our results establish a rat model of UT inhibition and demonstrate the diuretic efficacy of UT inhibition.

Role of renal prostaglandins in circulatory homeostasis

The evidence is reviewed that prostaglandins of renal origin through (i) their local actions on renal blood vessels, and (ii) complex interactions with the nervous adrenergic and the endocrine vasoactive renin-angiotensin-aldosterone and kallikrein-kinin systems, may participate in the regulation of excretory functions of the kidney and thereby contribute to circulatory homeostatic mechanisms.

Electrical conductivity measurements of urine as a new simplified method to evaluate the diuretic activity of medicinal plants

ETHNOPHARMACOLOGICAL RELEVANCE

Diuretic plants are widely used in traditional medicine in many countries. However, many of these species have not been subjected to experimental studies to confirm that property. In this paper, a simple new method is proposed to evaluate the diuretic activity of plants. We define a new index that takes into account only the volume of urinary excretion and total ion concentration excreted obtained by specific electrical conductivity measurements.

MATERIALS AND METHODS

Urine was collected in a graduate cylinder during the 8h after Artemisia thuscula (AT), Withania aristata (WA), Smilax canariensis (SC) and HCTZ oral administration to laboratory mice. To obtain the new index Diuretic Power (DP), we measured the specific electrical conductivity (κ) of the fresh urine samples. We calculated the concentration of a NaCl (or KCl) aqueous solution that has the same specific electrical conductivity as the urine sample. We multiplied this concentration by the corresponding urinary excretion volume, thus obtaining the total mEq. of electrolyte excreted "as if all were NaCl (or KCl)". Finally, we divided these mEq. by those corresponding to the control to obtain the DP value.

RESULTS

HCTZ showed a 40% increase in DP, with respect to the control group, independently of the doses used, and the studied plants produced an increase between 7 and 28%. DP values were compared with other common indexes, DI and SIi, showing that the variation sequence of the three indexes was the same for HCTZ, WA and SC.

CONCLUSIONS

A new and easy index, that we called diuretic power (DP), for estimating the diuretic activity of drugs or plants is proposed. It allows us to highlight diuretic effect with respect to a control value of a large amount of drugs or plants that had not been previously experimentally studied.

[Clinical significance of serum and urinary biomarkers for water-salt metabolism in patients with proteinuric forms of chronic glomerulonephritis]

AIM

To determine the nature and magnitude of changes in the detectable serum and urinary biomarkers of water-salt metabolism in patients with proteinuric forms of chronic glomerulonephritis (CGN), their importance for assessing the activity and prognosis of the disease.

SUBJECTS AND METHODS

Forty-seven patients with CGN were examined. Group 1 included 10 patients with nephrotic syndrome (NS) and decreased renal function; Group 2 comprised 16 patients with persistent NS and normal renal function; Group 3 consisted of 10 patients with partial remission of NS; Group 4 included 11 patients with active hematuric CGN. A control group consisted of 9 healthy individuals matched for gender and age with the patients with CGN. The serum level of copeptin and the urinary excretion of aquaporine-2 (AQP-2) and kidney injury molecule-1 (KIM-1) were determined by indirect enzyme-linked immunosorbent assay (ELISA).

RESULTS

In the NS patients with and without renal dysfunction, the serum copeptin concentration was significantly higher than that in those with partial remission of NS or hematuric CGN and in the controls. In the patients with hematuric CGN, this indicator was virtually different from that in the control group. Urinary AQP-2 excretion was significantly similar in 3 NS groups. In the patients with hematuric CGN, the urinary AQP-2 concentration was higher than that in those with NS, but it was significantly lower than in the control group. The highest urinary excretion of KIM-1 was found in the patients with NS and diminished renal function while its excretion was significantly lower in the patients with NS and stable renal function, as in those with partial remission of NS. The lowest values were seen in the patients with hematuric CGN and in the control group; the differences between these groups were statistically insignificant. Correlation analysis showed that there was an inverse correlation between serum copeptin and urinary AQP-2 levels and between urinary AQP- 2 and KIM-1 levels.

CONCLUSION

Serum copeptin levels and urinary AQP-2 secretion may be used to assess the activity of CGN and NS and to evaluate therapeutic effectiveness. The determination of urinary KIM-1 excretion may be of the same practical value in patients with NS. It has been shown that the concentrations of copeptin, APQ-2, and KIM-1 may be used as a differential diagnostic criterion for hematuric CGN.

Diuretic activity of some Smilax canariensis fractions

ETHNOPHARMACOLOGICAL RELEVANCE

Smilax canariensis is an endemic species of the Canary Islands, popularly known as "Zarzaparrilla sin espinas". The rhizome, leaves and stem of this species has wide use in folk medicine practice on the islands, where they are habitually employed as diuretic.

AIM OF THE STUDY

In this paper we report on the diuretic activity in experimental animals of several fractions of the methanol extract of this species.

MATERIALS AND METHODS

Four fractions of the methanol extract of the rhizomes, leaves and stem of Smilax canariensis (50 and 100mg/kg), Furosemide and Hydrochlorotiazide (10mg/kg), were orally administered to laboratory animals to evaluate their diuretic activity. Water excretion rate, pH, conductivity, and content of Na(+), K(+) and Cl(-) were measured in the urine of saline-loaded mice.

RESULTS

All the studied extracts showed an interesting increase of the diuresis, although the n-buthanol (27%; p<0.05) and ethyl acetate extract (35%; p<0.01), at 100mg/kg p.o., showed the most interesting diuretic activity, which suggested that this diuretic effect is associated with the compounds contained in the fractions of intermediate polarity (ethyl acetate and n-butanol), decreasing in the most extreme apolar and polar sub-extracts (dichloromethane and methanol: water respectively). The increase in diuresis produced by these two extracts was very close to the values of Hydrochlorothiazide (32%) or Furosemide (39%), used as reference diuretics.

CONCLUSIONS

These data, together with previous results on the aqueous and methanol extracts, reaffirm assertions made regarding the effectiveness of the extracts of this plant against urinary pathologies in the Canary Islands folk medicine.

[Consumption of table salt and psychological status in patients with arterial hypertension]

The frequency of neurotic disorder was studied in 630 patients with arterial hypertension (AH) who consumed large amounts of table salt (TS). Their threshold gustatory sensitivity to salt (TGS) was determined in conjunction with daily sodium excretion in urine and psychological features (using the SMOL test. MOS SF-36 questionnaire, and Zung depression scale). It was shown that AH patients consume 6-7 g more salt than healthy subjects due to the love of salty food and high TGS. Such patients are characterized by high activity and ambitiousness, and unrealized strive for obtaining a higher position. Their psychological status is dominated by anxiety, tension, and depression. The state of the vegetative nervous system is prevailed by sympaticotony.

Cerebral salt wasting syndrome in tuberculous meningitis

Case of a seventy year old female, who developed cerebral salt wasting syndrome in association with Tuberculous Meningitis is presented.

[Impaired gustatory sensitivity of the tongue to table salt as a risk factor of arterial hypertension]

The study included 630 patients with verified diagnosis of arterial hypertension (AH) in whom 24 hr AP monitoring was performed, threshold gustatory sensitivity of the tongue to table salt (TGS) measured, and habit to add salt to the cooked food evaluated. Measurement of Na in daily urine of 442 patients was followed by estimation of salt consumption. The results were compared with those obtained in 100 patients with newly diagnosed AH. The control group comprised 288 subjects. TGS in AH patients was significantly higher than in controls and directly related to clinical features of the disease, high AP values, age, smoking habits, hypercholesterolemia, abdominal-type obesity, and hereditary predisposition. TGS positively correlated with daily urinary excretion of NaCl (r = 0.4-0.7; p < 0.05-0.01). High TGS decreased under effect of hypotensive therapy.

Albuminuria, intermittent hyperfiltration and salt wasting in patients with stroke: a pilot study

OBJECTIVE

To investigate whether different types of stroke influence renal excretion of albumin, major electrolytes and water.

MATERIAL AND METHODS

Timed urine collections were started shortly after admission in 5 patients with haemorrhagic stroke (group A), 5 with ischaemic stroke (group Bx), 6 with presumed ischaemic stroke (groups By/z) and 6 with subarachnoid haemorrhage (group C). Albuminuria was also investigated in four patients undergoing elective abdominal surgery.

RESULTS

Increased levels of albuminuria were observed in all patients in groups A and B, but were found to decline with observation time and appeared to be related to outcome in group B. In group C, albuminuria was detected in 4 out of 6 patients. Elective surgery did not affect albumin excretion. In a setting with high urinary osmolality, high excretion rates for creatinine, urea, sodium, potassium and large diuresis were intermittently observed in groups A, B and C. None of these patients was in steady-state condition.

CONCLUSIONS

Different types of stroke elicit a complex change in renal function which resembles the response to a hypervolaemic and hyperosmolar signal, possibly mediated by a breakdown of renal autoregulation of blood flow in the presence of high vasopressin activity. Acute changes in excretion of albumin might be an indicator of prognosis in stroke. The findings point to the existence of unrecognized pathways between the central nervous system and the kidneys. Further studies on the mechanisms underlying alterations in renal function in stroke and their implication for treatment and outcome are indicated.

[Pseudohypoaldosteronism in infants with salt wasting syndrome. Two case reports]

The paper discusses two cases of male infants, who developed a markedly elevated salt wasting syndrome in early infancy, resistant to treatment with mineralocorticoids. Steroid urinary profiles excluded congenital adrenal hyperplasia. However, both patients presented with extremely high excretion of aldosterone metabolite THAldo without effects of aldosterone action, what resulted in pseudohypoaldosteronism (PHA) diagnosis. The patients were treated with sodium supplementation, which normalized their clinical state and serum electrolytes. In the first patient the sporadic form of renal PHA1 is suspected. In the second patient congenital urinary tract anomalies and infection resulted in transient PHA1. Pseudohypoaldosteronism should be considered in the differential diagnosis of a salt wasting syndrome in infants, especially when it is accompanied by infections or congenital defects of the urinary tract.

Control of potassium excretion: a Paleolithic perspective

PURPOSE OF REVIEW

Regulation of potassium (K) excretion was examined in an experimental setting that reflects the dietary conditions for humans in Paleolithic times (high, episodic intake of K with organic anions; low intake of NaCl), because this is when major control mechanisms were likely to have developed.

RECENT FINDINGS

The major control of K secretion in this setting is to regulate the number of luminal K channels in the cortical collecting duct. Following a KCl load, the K concentration in the medullary interstitial compartment rose; the likely source of this medullary K was its absorption by the H/K-ATPase in the inner medullary collecting duct. As a result of the higher medullary K concentration, the absorption of Na and Cl was inhibited in the loop of Henle, and this led to an increased distal delivery of a sufficient quantity of Na to raise K excretion markedly, while avoiding a large natriuresis. In addition, because K in the diet was accompanied by 'future' bicarbonate, a role for bicarbonate in the control of K secretion via 'selecting' whether aldosterone would be a NaCl-conserving or a kaliuretic hormone is discussed.

SUMMARY

This way of examining the control of K excretion provides new insights into clinical disorders with an abnormal plasma K concentration secondary to altered K excretion, and also into the pathophysiology of calcium-containing kidney stones.

Long-term compliance with salt restriction in Japanese hypertensive patients

The purpose of the present study was to investigate the long-term compliance with salt restriction in Japanese hypertensive patients. Subjects included 389 patients, 230 women and 159 men, mean age 58+/-11 years, who underwent successful 24-h home urine collection more than three times over an interval of a year. Urinary salt, potassium, and creatinine were measured. Additionally, family history, habitual alcohol intake, smoking habit, physical activities, and job status were assessed by use of a questionnaire. During the follow-up period (average 3.5 years), participants underwent urine collection 4.6 times in average. Urinary salt excretion at the last visit was significantly lower than that at the first visit (8.7+/-3.4 vs. 9.6+/-4.1 g/day; p<0.01). Urinary potassium excretion also decreased significantly during this period (from 2.0+/-0.7 to 1.9+/-0.7 g/day; p<0.05). Among the mean 4.6 urine collections, 45.2% (men 34.6%, women 52.6%) of the patients successfully achieved <6 g (100 mmol of sodium)/day of salt excretion on at least one occasion. The rate of achievement of averaged urinary salt excretion <6 g/day dropped to 10.3% (men 4.4%, women 14.3%). Only 2.3% (men 0.6%, women 3.5%) of the patients achieved <6 g/day on all occasions. There were no significant differences in age, habitual alcohol intake, smoking habit, physical activities, or job status between patients who complied with the salt-restricted diet and those who did not. Results suggest that long-term compliance with salt restriction is poor in Japanese hypertensive patients. Since no specifically defining characteristics were found in the compliant patients, repeated measurements of urinary salt excretion seem to be important to encourage salt restriction.

Determination of discretionary salt intake in an iodine deficient area of East Java-Indonesia using three different methods

As salt is a potential vehicle for delivering iodine to a population, study on salt intake is important. Many methods have been used to measure iodised-salt intake, but the methods were suspected to be inaccurate. A new method, called a lithium-marker technique, has been considered as suitable and safe; hence it has been proposed as a gold standard for measuring the actual salt intake of an individual. We conducted a study to determine discretionary salt intake using the lithium marker technique. The study shows that the total salt intake for children (N = 15) and mothers (N = 15) were 5.4+/-2.1 g/d and 5.8+/-1.7 g/d respectively in which 48.5+/-17.1% and 50.5?17.3% were discretionary salt. The discretionary salt intake measured using lithium marker (2.53 +/- 1.2 g/d for children and 2.99 +/- 1.5 g/d for mother) were significantly lower than using 24-hour salt recall (7.01+/-2.44 g/cap/d) and salt weighing (6.00+/-1.8 g/cap/d) (p<0.001). In conclusion, the discretionary salt intake by 24-hour salt recall and salt weighing were over estimated as compared to the lithium-labelled salt measurement. It is recommended that the level of iodine fortification in salt be increased up to 80-100 ppm of KIO3 to provide iodine intake of 150 microg/d.

Brain ouabain stimulates peripheral marinobufagenin via angiotensin II signalling in NaCl-loaded Dahl-S rats

OBJECTIVE

In NaCl-loaded Dahl salt-sensitive (DS) rats the transient stimulation of brain endogenous ouabain (EO) precedes the increase in renal excretion of marinobufagenin (MBG), a vasoconstrictor and natriuretic. In hypertensive DS rats, EO raises blood pressure (BP) via an ATII-sensitive pathway. We hypothesized that an NaCl-induced increase in MBG is linked to the EO-stimulated ATII pathway.

METHODS

We studied the effects of 3 h of NaCl loading (17 mmol/kg, intraperitoneally) in male DS rats treated with antibodies to MBG or ouabain, or with losartan (25 mg/kg).

RESULTS

NaCl loading alone induced a transient stimulation of pituitary EO (22.4 +/- 1.8 versus 12.2 +/- 1.3 pmol/g) and ATII (39.4 +/- 2.8 versus 18.4 +/- 3.2 ng/g), a sustained increase in MBG excretion (5.2 +/- 0.6 versus 1.1 +/- 0.2 pmol/h), a 40% inhibition of the renal sodium pump, a natriuretic response, a 35 mmHg increase in systolic BP, and an increase in adrenocortical ATII and MBG levels and in plasma norepinephrine. The anti-MBG antibody reduced the natriuresis (36%) and BP (40 mmHg), and restored renal sodium pump activity. The anti-ouabain antibody prevented the increase in pituitary ATII, reduced MBG excretion, natriuresis and BP, increased sodium pump activity, and prevented increases in plasma norepinephrine, pituitary and adrenocortical ATII, and adrenocortical MBG. Losartan mimicked the effects of the anti-ouabain antibody, but did not affect the excretion of EO. In adrenocortical cells of DS rats, ATII stimulated MBG secretion, and losartan blocked this effect.

CONCLUSIONS

In response to NaCl loading, brain EO, via an AT1 receptor pathway and probably via sympathetic activation, stimulates adrenocortical MBG, which inhibits the renal sodium pump and elevates BP.

Cerebral salt wasting in subarachnoid hemorrhage rats: model, mechanism, and tool

Cerebral salt wasting (CSW) frequently occurs concomitantly with aneurysmal subarachnoid hemorrhage (SAH). CSW induces excessive natriuresis and osmotic diuresis, and reduces total blood volume. As a result, the risk of symptomatic cerebral vasospasm may be elevated. Therefore, it is important to determine the mechanism of CSW. The purpose of this study was to evaluate whether the rat SAH model exhibits CSW and to investigate the relationship between CSW and natriuretic peptides. A SAH model was produced in 24 rats by perforating a cerebral artery with a nylon thread up through the common carotid artery. To evaluate CSW, urine was cumulatively collected from SAH onset to 12 hours and sodium (Na) excretion was analyzed. Body weight and hematocrit were analyzed before and after SAH onset. Concentrations of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) in plasma were also analyzed. Urine volume and total Na excretion of SAH rats were significantly higher than those of sham rats (p<0.05). Body weight of SAH rats significantly decreased and hematocrit significantly increased (p < 0.05). ANP concentration was significantly decreased in SAH rats (p<0.05). However, BNP concentrations did not change. This study demonstrated for the first time that a rat SAH model exhibited CSW. It was suggested that the cause of CSW was neither ANP nor BNP. In addition, this rat SAH model will be useful for study of CSW after SAH.

Fetal obstructive uropathy: is urine sampling useful for prenatal counselling?

OBJECTIVES

To evaluate whether fetal urinary sodium and chloride provide clinically useful information in addition to ultrasound in bilateral obstructive uropathy.

METHODS

Sonographic features and urinary concentrations of sodium and chloride were evaluated in fetuses with bilateral obstructive uropathy. After a minimum of 12 months of postnatal follow-up, cases that developed increased serum creatinine (greater than 50 micromol/L) were compared with those that did not.

RESULTS

Of the cases studied, 16/35 died perinatally, all showing anamnios and markedly elevated urinary electrolytes. Of the survivors, ten maintained normal postnatal serum creatinine, whereas nine did not. The frequency of reduced amniotic fluid/olygohydramnios was higher in cases that developed increased serum creatinine (four out of nine) than in those that did not (nil). Sodium above the 95th percentile was 100% specific and 44% sensitive to predict an increased serum creatinine during early infancy, while chloride above the 95th percentile was 70% specific and 56% sensitive. All seven cases in which urinary sodium was elevated and/or amniotic fluid volume was reduced developed renal failure.

CONCLUSION

Urine sampling slightly improved renal function prediction, but this must be balanced against its fetal risks.

Investigation of matrix effects of urine on a molecularly imprinted solid-phase extraction

This study investigates matrix effects on a molecularly imprinted solid-phase extraction (MISPE) method developed for the clean-up of diphenyl phosphate (a hydrolysis product of the commonly used flame retardant and plasticizer, triphenyl phosphate) in urine samples. The influence of potentially interfering compounds that naturally occur in urine was examined with respect to extraction recovery, repeatability and selectivity. The components tested were NaCl, urea, creatinine and hippuric acid. The imprinted polymer was prepared using 2-vinylpyridine as the functional monomer, ethylene glycol dimethacrylate as crosslinker and a structural analogue of the analyte as the template molecule. The recovery of diphenyl phosphate from water standards was over 90% using MISPE, compared to less than 25% using a non-imprinted SPE (NISPE) counterpart. The selectivity of MISPE compared to NISPE was achieved in a wash step with a basic modifier in methanol. The recovery and repeatability of the MISPE method were affected most by NaCl in the tested concentrations, while urea, creatinine and hippuric acid had no significant influence. NaCl most likely weakens the binding during the loading of the sample. This effect could be suppressed by diluting the sample with a citrate buffer at pH 4.0.

Low sodium excretion in SIADH patients with low diuresis

It is well known that during low diuresis or low effective circulating volume, salt excretion is low. The aim of this study was to find out whether salt excretion, expressed as either urinary sodium concentration (UNa) or fractional sodium excretion (FENa), and the combined use of FENa and fractional urea excretion (FEurea) still differentiate between hyponatremic SIADH and hyponatremic salt depletion (SD) patients when diuresis is low. The relationships between UNa, FENa and diuresis, indirectly estimated by the urinary to plasma creatinine ratio (U/P creat), were studied in 42 hyponatremic SIADH patients, 21 hyponatremic SD patients and 66 normonatremic controls (CO) of similar age and sex ratio. There was no significant relationship between UNa and U/P creat either in SIADH or in SD or CO patients. FENa and U/P creat were inversely correlated, both in CO (r = -0.72; p < 0.001) and in SIADH (r = -0.68; p < 0.001). SIADH and SD patients can be fairly well differentiated from one another using FENa and U/P creat. Even with high U/P creat values, SIADH patients, despite a sharp decrease in their FENa values, presented still higher FENa values than SD patients did (mean FENa = 0.3 +/- 0.2% in SIADH and 0.1 +/- 0.04% in SD; p < 0.05). However, FENa values of SIADH patients with low diuresis (mean FENa = 0.3 +/- 0.2% for a mean U/P creat = 191 +/- 40) are indistinguishable from those of SD patients with normal urine volumes (mean FENa = 0.2 +/- 0.2% for a mean U/P creat = 92 +/- 30). The combined use of FENa and FEurea remains a reliable way to discriminate SD patients and SIADH patients, as far as the differential limit value for FENa is narrowed to a value of 0.15%, for hyponatremic patients with U/P creat >140.

CONCLUSION

In SIADH, FENa values are lower than 0.5%, as soon as U/P creat exceeds a value of 180. In SD patients with U/P creat values exceeding 140, FENa is lower than 0.15% and FEurea lower than 45%.

Spinal anesthesia for arthroscopic knee surgery

BACKGROUND AND OBJECTIVE

The purpose of the study was to compare the effects of adding 50 microg of morphine, 25 microg of fentanyl or saline to 6 mg of hyperbaric bupivacaine on postoperative analgesia and time to urination in patients undergoing arthroscopic knee surgery under spinal anesthesia.

METHODS

The study was designed in a prospective, randomized, double-blinded and placebo-controlled manner. Sixty ASA I-II patients were randomized into the following three groups: Group BM: 6 mg of bupivacaine and 50 microg of morphine, Group BF: 6 mg of bupivacaine and 25 microg of fentanyl, and Group BS: 6 mg of bupivacaine and saline. Selective spinal anesthesia was performed in a lateral decubitus position, with the operative knee dependent for 10 min.

RESULTS

In all groups satisfactory anesthesia was provided during the operation. There was a statistically significant difference between all the groups in times to voiding [Group BM 422 +/- 161 min; Group BF 244 +/- 163 min; Group BS 183 +/- 54 min (mean +/- SD)]. The incidence of pruritus was significantly greater in Group BM (80%) and BF (65%) in comparison with Group BS (no pruritus) (P < 0.05). The incidence of nausea was significantly increased in Group BM (35%) in comparison with Group BF (10%) and Group BS (P < 0.05). Analgesic consumption was significantly greater in Group BS in comparison with Groups BM and BF (P < 0.01).

CONCLUSIONS

We conclude that during spinal anesthesia even mini-dose intrathecal morphine is not acceptable for outpatient surgery due to side-effects, especially severely prolonged time to urination.

Effects of the peroxisomal proliferator-activated receptor-gamma agonist pioglitazone on renal and hormonal responses to salt in healthy men

Glitazones are used in the treatment of type 2 diabetes as efficient insulin sensitizers. They can, however, induce peripheral edema through an unknown mechanism in up to 18% of cases. In this double-blind, randomized, placebo-controlled, four-way, cross-over study, we examined the effects of a 6-wk administration of pioglitazone (45 mg daily) or placebo on the blood pressure, hormonal, and renal hemodynamic and tubular responses to a low (LS) and a high (HS) sodium diet in healthy volunteers. Pioglitazone had no effect on the systemic and renal hemodynamic responses to salt, except for an increase in daytime heart rate. Urinary sodium excretion and lithium clearance were lower with pioglitazone, particularly with the LS diet (P < 0.05), suggesting increased sodium reabsorption at the proximal tubule. Pioglitazone significantly increased plasma renin activity with the LS (P = 0.02) and HS (P = 0.03) diets. Similar trends were observed with aldosterone. Atrial natriuretic levels did not change with pioglitazone. Body weight increased with pioglitazone in most subjects. Pioglitazone stimulates plasma renin activity and favors sodium retention and weight gain in healthy volunteers. These effects could contribute to the development of edema in some subjects treated with glitazones.

Different responses of atrial natriuretic peptide secretion and its receptor density to salt intake in rats

This study investigated whether high-salt intake influences atrial natriuretic peptide (ANP) system, atrial content, and release rate of ANP as well as receptor density in the kidney were measured in salt intake rats. Male Sprague-Dawley rats received either 0.9% or 2% salt in their drinking water for 10 days. The stretch-induced ANP secretion from isolated perfused non-beating left atria was accentuated, and the production of cGMP by ANP in renal cortical tissue membranes were pronounced in rats exposed to 0.9% salt for 10 days but not in rats exposed to 2% salt. The levels of ANP receptor density and expression in renal cortex were decreased in 2% salt intake rats but not in 0.9% salt intake rats. No significant differences in atrial and plasma concentrations of ANP and water balance were observed in both salt intakes. Therefore, these results suggest that atrial ANP secretion and its binding sites in the kidney may respond differently to ingested salt concentrations in rats.

Reduced sodium output following acute spinal injury

STUDY DESIGN

Assessment of sodium output in spinal injury patients.

OBJECTIVES

The purpose was to examine the effects of sodium loading acutely by an infusion, long term by sodium supplements, to acutely injured spinal patients on a fixed sodium intake. This was compared with another group of acutely injured patients who were on a hospital diet of between 50 and 150 mmol of sodium daily.

SETTING

The National Spinal Injuries Centre, Stoke Mandeville Hospital, Aylesbury, Bucks HP21 8AL, UK.

METHODS

A total of 53 studies were carried out on 52 patients between 1962 and 1964. In all, 49 patients were studied during the first 10 days after injury as follows: a control group of 39 patients received no supplementary sodium, two received NaCl infusion, two NaCl tablets orally, and six received NaCl infusion followed by NaCl tablets orally. Four patients were studied for more than 15 days after injury (one of these had been studied in the acute stage); they received NaCl infusion and one (42d) received in addition NaCl tablets for four subsequent days.

RESULTS

In all patients urinary sodium excretion was minimal on day 2 and increased thereafter. On days 2-6, it was significantly lower in patients with a complete transection of the cervical cord than in patients with lower lesions. In the early studies, nine patients excreted less than 40% of the administered load within 24 h. In four of these patients excretion was 10% or less. In the later studies, three of the four patients excreted at least 80% of the infused Na+ on the same day.

CONCLUSION

Sodium retention in the patient with cord injury is a response to trauma. The different responses seen in patients with different levels of cord transection are not due to direct changes in the innervation of the kidney but to compensation for sympathetic insufficiency, blood pressure being maintained by the secretion of aldosterone, vasopressin and other hormones. The decreased urinary output seen acutely after cord transection is not due to renal failure and the patient's condition can be made dangerously worse by attempts to create a diuresis.

Stages of Change for Salt Intake and Urinary Salt Excretion: Baseline Results from the High-Risk and Population Strategy for Occupational Health Promotion (HIPOP-OHP) Study

We investigate the relationship of urinary salt excretion to the stage of change to decrease salt intake in the Japanese diet. The data reported here were obtained from a baseline survey of the High-Risk and Population Strategy for Occupational Health Promotion (HIPOP-OHP) study that was conducted as a non-randomized control trial at 12 worksites in Japan. A total of 6,816 subjects (5,410 male, 1,406 female) were used in 1999 and 2000 for the analysis. We used three categories of stage of change: precontemplation or contemplation (P/C), preparation (P), and action or maintenance (A/M). Urinary salt excretion was estimated from the sodium and creatinine concentrations in spot urine samples. Multivariate analysis indicated that urinary salt excretion among males was 0.3 g/day greater in the P/C stage than in the A/M stage (p < 0.05). For non-obese females, urinary salt excretion in the P/C stage was 0.6 g/day greater than in the A/M stage (p < 0.05). Multivariate analysis showed that diastolic blood pressure in males not taking antihypertensive agents was 1.3 mmHg lower in the P/C stage than in the A/M stage (p < 0.05). A similar but statistically insignificant tendency was observed among non-obese females. A significant association was demonstrated between stage of change for dietary salt intake and urinary salt excretion for both males and non-obese females. There may be a potential application of the stage of change model for reducing dietary salt intake in a health promotion program.

Intracranial renin alters gustatory neural responses in the nucleus of the solitary tract of rats

Activation of the renin-angiotensin system in the brain is considered important in the arousal and expression of sodium appetite. To clarify the effects of directly activating this hormonal cascade, taste neurons in the nucleus of the solitary tract of rats were tested with a battery of sapid stimuli after intracerebroventricular injection of renin or its vehicle. The rats were chronically prepared but lightly anesthetized during the recording procedure. Eighty-five taste neurons were tested: 46 after renin injections and 39 after vehicle. Neural activity was counted for 5.0-s periods without stimulation (spontaneous) and during stimulation with water and sapid chemicals. The averaged responses to each of the standard stimuli (0.1 M NaCl, 0.3 M sucrose, 0.01 M citric acid, and 0.01 M quinine hydrochloride) did not differ significantly between the two conditions. When the rats were tested with a concentration range of NaCl, however, after renin the average responses to the hypertonic 0.3 and 1.0 M stimuli were reduced to 74 and 70%, respectively, compared with those after vehicle injections. A similar tendency was evident for the subsample of neurons that responded best to NaCl, but the effect was smaller. These data are consistent with, but not as dramatic as, those reported after dietary-induced sodium appetite.

Prevention of human deconditioning during prolonged immersion in water

A 56-day immersion experiment in which two subjects participated was carried out. During the experiment the preventive effect of periodic acceleration combined with exercise and water-salt intake was assessed. Simulating an increased gravitational field, exposure to acceleration increased the static component of the load upon the musculo-skeletal system, increased the gradient of the blood hydrostatic pressure, activated mechanisms responsible for the venous return to the heart, stimulated systems regulating antidiuretic and antisodiumdiuretic reflexes. Involvement of these mechanisms restored haemodynamic parameters, fluid-electrolyte balance and blood coagulability. The prophylactic effect of acceleration was enhanced if combined with exercise and supplemented water-salt intake.

Urinary level of 1,N(6) -ethenodeoxyadenosine, a marker of oxidative stress, is associated with salt excretion and omega 6-polyunsaturated fatty acid intake in postmenopausal Japanese women

Excretion of 1,N(6)-ethenodeoxyadenosine (epsilon dA), a marker for lipid peroxidation (LPO)-derived DNA damage was analyzed in urine of nonsmoking postmenopausal women participating in a dietary intervention trial in Northern Japan. Hereby the efficacy of dietary consultation in reducing salt and increasing vitamin C and carotenes during 1 year was estimated. Thirty postmenopausal women, 60-69 years of age, from the intervention group and 30 age-matched women from the control group were randomly selected. The subjects completed a self-administered diet history questionnaire and in the pre- and post-intervention period 48 hr urine and fasting blood samples were collected. epsilon dA in urine was analyzed by an immuno-precipitation-high performance liquid chromatography-fluorescence detection method. epsilon dA excretion (/48 hr) in the 59 postmenopausal Japanese women with complete urine collection ranged from 12-226 pmol at the pre-intervention. At the pre-intervention, epsilon dA excretion was positively associated with urinary salt excretion (R = 0.33, p = 0.01) and omega-6 polyunsaturated fatty acid intake (%energy value, R = 0.28, p = 0.03) in the 59 women. The average epsilon dA excretion in the intervention group was 61 pmol at pre-intervention and 44 pmol at post-intervention (p = 0.14). In the control group, it was 58 pmol at pre-intervention and 75 pmol at post-intervention (p = 0.24). During the intervention period, 18/29 (62%) of the subjects in the intervention group exhibited the decreased excretion and 10/26 (38%) in the control group (p = 0.08). Results from this pilot study suggest urinary epsilon dA as a potential biomarker of DNA damage possibly derived from salt-induced inflammation and LPO; further exploration of epsilon dA in human biomonitoring studies is warranted.

Fetal uninephrectomy leads to postnatal hypertension and compromised renal function

It has been proposed that the number of nephrons an individual has may be inversely related to his or her blood pressure. In this study using female ovine fetuses, nephron number was reduced by performing a fetal uninephrectomy during the period of active nephrogenesis (100 days of gestation, term=150 days). Lambs were born at term and grew at a similar rate. At 5 months of age, ovaries were removed and the carotid artery exteriorized into a fold of skin. Blood pressure and renal function were studied at 6 and 12 months of age. At 6 months of age, uninephrectomized lambs had significantly higher mean arterial blood pressure than sham-operated lambs (89+/-2 versus 82+/-2 mm Hg, P<0.05) when measured over a 3-day period. Heart rate was not different between the groups. Urine flow rate was similar, but glomerular filtration rate was significantly lower in uninephrectomized animals (P<0.05). Urinary concentrations and excretion rates of sodium tended to be higher in uninephrectomized animals but were similar for chloride and potassium. There was no evidence of proteinuria in the uninephrectomized lambs. Similar differences were observed in blood pressure and renal function at 12 months of age. Plasma renin concentrations at this age were lower in the uninephrectomized lambs (P<0.05). An oral salt load for 10 days did not increase blood pressure significantly in either group at 12 months of age, nor were there differences in the responsiveness to graded doses of angiotensin II. These results suggest that formation of a low nephron number in utero, may result in elevated blood pressure and compromised renal function in later life.

Endogenous ligand of alpha(1) sodium pump, marinobufagenin, is a novel mediator of sodium chloride--dependent hypertension

BACKGROUND

Digitalis-like sodium pump ligands (SPLs) effect natriuresis via inhibition of renal tubular Na(+),K(+)-ATPase but may induce vasoconstriction. The present study investigated the potential roles of 2 putative endogenous SPLs, an ouabain-like compound (OLC) and an alpha(1) Na(+),K(+)-ATPase inhibitor, marinobufagenin (MBG), in regulating natriuresis and blood pressure (BP) responses to sustained and acute NaCl loading in Dahl salt-sensitive rats (DS).

METHODS AND RESULTS

During 4 weeks of an 8% NaCl diet, DS exhibited a progressive increase in MBG renal excretion (66 +/-13 pmol/24 hours at week 4 versus 11 +/- 1 pmol/24 hours at baseline, n=48), which paralleled an increase in systolic BP (174 +/- 10 mm Hg at week 4 versus 110 +/- 2 mm Hg at baseline). By contrast, OLC excretion peaked at week 1 and returned to baseline levels. Administration of an anti-MBG, but not anti-ouabain antibody, to DS after 3 weeks of a high NaCl diet lowered BP (139 +/- 7 versus 175 +/- 5 mm Hg, P<0.001, n=5). Acute NaCl loading (2 hours) of DS (n=5) increased MBG and OLC excretion and natriuresis. Pretreatment of acutely NaCl-loaded DS with an anti-MBG antibody (n=5) reduced the excretion of sodium and MBG but not that of OLC. An anti-ouabain antibody (n=5) reduced sodium excretion and both OLC and MBG.

CONCLUSIONS

An initial transient stimulation of OLC induced by NaCl loading of DS precedes an MBG response. A sustained increase in MBG production in DS contributes to the chronic BP elevation induced by a sustained high NaCl intake.

Renal handling of salt and water in humans during exercise with or without hydration

Plasma sodium (Na+) concentration, i.e. natraemia, results from body tonicity equilibrium. During exercise, a change in body tonicity can result from an imbalance between intake and loss of Na+, potassium (K+) and water (H2O) due to renal and/or extra-renal mechanisms. Whether exercise-induced changes in kidney function could be responsible for such an imbalance was studied by measuring glomerular filtration rate (creatinine clearance), proximal tubule activity (lithium clearance) and renal handling of Na+ and K+ at rest and during exercise. Since hyponatraemia during or after exercise has been reported, we also investigated whether a water load could be appropriately excreted during exercise. Ten young men pedalled on a cycle ergometer at 60% of maximal oxygen uptake for 45 min with (HE, hydrated exercise) or without (DHE, dehydrated exercise) a supply of water. In both conditions, creatinine, lithium, and electrolyte (Na+ + K+) clearances decreased and natraemia did not change. The DHE induced a loss of body mass (-1.29%), decreased diuresis and large extra-renal water loss [mean (SEM)] [880 (73) ml]. The HE led to no loss in body mass, increased diuresis and lower extrarenal water loss [680 (48) ml]. Electrolyte-free water excretion, negative for DHE, represented 60% of diuresis during HE. Thus the kidney, by increasing electrolyte reabsorption mainly in the proximal tubule, and appropriately excreting a water load, seems efficacious in regulating extracellular fluid volume and body tonicity and so not responsible for the imbalance between (Na+ + K+)/H2O intake and loss. Therefore, extra-renal changes could be the main causes of exercise-induced tonicity imbalances which could ultimately lead to dysnatraemia.

Evaluation of various rapid chloride tests for assessing urinary NaCl excretion

BACKGROUND/AIMS

The evidence linking NaCl intake to high blood pressure and probably to other diseases has become stronger. Therefore, a population-wide reduction of NaCl intake is generally recommended. Measuring NaCl excretion in urine is the preferred method for estimating dietary NaCl intake. Rapid tests measuring urinary NaCl excretion might be useful for self-monitoring the individual NaCl consumption.

METHODS

The accuracy of four rapid tests measuring chloride content in urine was assessed. Three tests were originally not designed for urine analysis, but for water and food analysis. Totally 204 urine samples were analysed both with the 4 different rapid tests and with quantitative routine laboratory procedures for chloride and sodium.

RESULTS

Chloride and sodium were highly correlated (r = 0.96), indicating chloride determination as a reasonable method to assess sodium and NaCl contents in urine. Accuracy of the rapid tests was acceptable in three cases. The drawback of two tests was their narrow calibration range, so that most urine samples had to be diluted. Use of one test showed problems in interpreting its results because the decolouration of the test pads was difficult to recognize.

CONCLUSION

It is concluded that rapid chloride tests designed for water analysis might be suitable to determine NaCl in urine samples.

Hyponatremia in intracranial disorders

Hyponatremia is a common electrolyte disturbance following intracranial disorders. Hyponatremia is of clinical significance as a rapidly decreasing serum sodium concentration as well as rapid correction of chronic hyponatremia may lead to neurological symptoms. Especially two syndromes leading to hyponatremia in intracranial disorders need to be distinguished, as they resemble each other in many, but not all ways. These are the syndrome of inappropriate ADH secretion (SIADH) and the cerebral salt wasting syndrome (CSW). The syndrome of inappropriate ADH secretion is characterized by water retention, caused by inappropriate release of ADH, leading to dilutional hyponatremia. The cerebral salt wasting syndrome on the other hand, represents primary natriuresis, leading to hypovolemia and sodium deficit. SIADH should be treated by fluid restriction, whereas the treatment of CSW consists of sodium and water administration. However, in the literature there is abundant evidence that hyponatremia in intracranial diseases is mostly caused by CSW. Therefore, treatment with fluid and salt supplementation seems indicated in patients with intracranial disorders who develop hyponatremia and natriuresis.

Renal effects of serine-7 analog of lymphoguanylin in ex vivo rat kidney

Guanylin and uroguanylin compose a family of natriuretic, diuretic, and kaliuretic peptides that bind to and activate apical membrane receptor guanylyl cyclase signaling molecules in renal and intestinal epithelia. Recently, a complementary DNA encoding an additional member of the guanylin family of cGMP-regulating peptides was isolated from lymphoid tissues of the opossum and was termed lymphoguanylin (LGN). A peptide analog of opossum LGN was synthesized containing a single disulfide bond with the internal cysteine-7 replaced by a serine residue (LGN(Cys7-->Ser7)). The biological activity of LGN(Ser) was tested by using a cGMP bioassay with cultured T84 (human intestinal) cells and opossum kidney (OK) cells. LGN(Ser) has potencies and efficacies for activation of cGMP production in the intestinal and kidney cell lines that are 100- and 1,000-fold higher than LGN, respectively. In the isolated perfused rat kidney, LGN(Ser) stimulated a maximal increase in fractional Na+ excretion from 24.8 +/- 3.0 to 36.3 +/- 3.3% 60 min after administration and enhanced urine flow from 0.15 +/- 0.01 to 0.24 +/- 0.01 ml. g(-1). min(-1). LGN(Ser) (0.69 microM) also increased fractional K+ excretion from 27.3 +/- 2.3 to 38.0 +/- 3.0% and fractional Cl- excretion from 26.1 +/- 0.8 to 43.5 +/- 1.9. A ninefold increase in the urinary excretion of cGMP from 1.00 +/- 0.04 to 9.28 +/- 1.14 pmol/ml was elicited by LGN(Ser), whereas cAMP levels were not changed on peptide administration. These findings demonstrate that LGN(Ser), which contains a single disulfide bond like native LGN, activates guanylyl cyclase-C (GC-C) receptors in T84 and OK cells and may be very helpful in studying the physiological importance of activation of GC-C in vivo. LGN(Ser) also exhibits full activity in the isolated perfused kidney equivalent to that observed previously with opossum uroguanylin, suggesting a physiological role for LGN in renal function. Thus the single amino acid substitution enhances the activity and potency of LGN.

Volume-induced natriuresis in healthy women: renal metabolism of prostacyclin and thromboxane, and physiological role of prostanoids

In healthy women submitted to a short-term expansion in extracellular fluid volume we have evaluated the urinary excretory profile of the stable metabolites of prostaglandin(PG) I2 and thromboxane(TX) A2, 6-keto-PGF1 alpha(6KPGF) and TXB2 respectively, and assessed the physiological role played by the prostanoids in this experimental condition. Salt retention (SR group, n=9) was induced by repeated i.v. infusion of saline solution (0.9% NaCl). At the end of the treatment the body weight had increased by 0.7+/-0.2 kg (mean+/-SEM) (P<0.05). Renal functional exploration [clearance (cl.) method] was performed during hypotonic polyuria (induced by oral water load) and subsequent moderate antidiuresis (induced by low-dose infusion of an antidiuretic hormone analogue). Urinary 6KPGF and TXB2 concentrations were estimated by RIA method during polyuria (P cl. period), early and late antidiuresis (A1 and A2 cl. periods). Paired functional explorations were performed in absence (control study) and presence of indomethacin. Basal values of plasma sodium and potassium concentrations, plasma renin activity (PRA) and urinary aldosterone excretion were determined just before the control study. The results in salt retention were compared to those previously obtained in healthy women submitted to a moderate salt depletion (SD2 group, n=6), in absence and presence of the drug. Women in salt retention received 100 mg i.m. of the drug, whereas salt-depleted women received only a halved dose as in previous studies in salt depletion the full dose produced prolonged anuria. (I) Salt retention vs salt depletion. The basal values of PRA and urinary aldosterone excretion were significantly lower. During polyuria, urinary excretion of 6KPGF, 6KPGF/TXB2 ratio, urinary flow rate, creatinine cl. and absolute and fractional excretions of sodium and chloride were significantly higher. In salt retention during polyuria, significant positive correlations were found between 6KPGF excretion and functional excretory parameters. (II) Indomethacin in salt retention. The following effects were significant: (a) a reduction in prostanoid excretions in P and A1 cl. periods only; (b) during polyuria, an increase in arterial pressure, a reduction in urinary flow rate and creatinine cl. (saluresis showed not significant reduction). During polyuria significant positive correlations occurred between the absolute effects of indomethacin on 6KPGF excretion and those on functional excretory parameters. (III) Comparative effects of indomethacin in salt retention and salt depletion. Despite the double dosage of the drug, the significant reductions in urinary metabolite excretions were not significantly different during P cl. period and significantly lower in A1 cl. period compared to the corresponding significant reductions in salt depletion. During polyuria, the significant increase in arterial pressure was significantly different from the not significant effect in salt depletion; the not significant effect on saluresis was significantly different from the significant reduction in salt depletion. The results suggest the following conclusions: (1) The present model showed the functional pattern of the volume-natriuresis; (2) In salt retention, in contrast with salt depletion, indomethacin induced an increase in arterial pressure consistent with the inhibition of a PG-dependent vasodilator mechanism active at the systemic level; (3) In salt retention, in contrast with salt depletion, indomethacin failed to induce a significant reduction in saluresis. This failure can be attributed to the drug's blunted effectiveness in inhibiting the renal synthesis of saluretic PGs, and probably to the interference of the concurrent increase in arterial pressure in the renal treatment of sodium and chloride.

Impact of aldosterone on left ventricular structure and function in young normotensive and mildly hypertensive subjects

Left ventricular (LV) hypertrophy is an independent risk factor for cardiovascular morbidity and mortality. Experimental data revealed that elevated circulating aldosterone is associated with increased collagen accumulation resulting in myocardial fibrosis. To analyze whether aldosterone is also associated with cardiac structural and functional changes in humans, we examined the effects of aldosterone on LV structure and function before and after suppression of aldosterone by increasing oral salt intake. The study group comprised 26 normotensive male white healthy control subjects (age 26 +/- 3 years) and 31 male white subjects (age 25 +/- 3 years) with mild essential hypertension (World Health Organization stages I to II). Two-dimensional-guided M-mode echocardiography and 24-hour ambulatory blood pressure (BP) monitoring was performed in each subject. Simultaneously, we measured 24-hour urinary sodium excretion, 24-hour urinary aldosterone, and serum aldosterone concentration at baseline and after increasing oral salt intake to suppress aldosterone secretion. In all subjects LV mass correlated with body mass index (r = 0.42, p <0.001) and both 24-hour ambulatory systolic (r = 0.28, p <0.05) and diastolic (r = 0.25, p <0.05) BP. Changes in urinary sodium excretion correlated inversely with changes in serum aldosterone concentration (r = -0.28; p <0.05). Urinary aldosterone concentration after salt loading decreased in normotensive (10.98 vs 7.44 microg/24 hours; p <0.02) but not in hypertensive (9.34 vs 10.51 microg/24 hours; p = NS) subjects. Serum and urinary aldosterone levels at baseline were not related to LV structure or function. In contrast, after increasing oral salt intake, urinary aldosterone concentration was related to LV mass (r = 0.43; p <0.01) and impaired midwall fractional fiber shortening (r = -0.33; p <0.02) in all subjects, independent of 24-hour ambulatory BP. Subgroup analysis revealed that this was significant only in hypertensive (r = 0.46; p <0.01 and r = -0.44; p <0.02, respectively) but not in normotensive (r = 0.28 and -0.16; p = NS for both, respectively) subjects. Consistently, the greater serum aldosterone remained after increasing oral salt intake, the greater was LV mass (r = 0.35; p <0.01). The latter was found in hypertensive subjects (r = 0.44; p <0.02), independent of 24-hour ambulatory BP, but not in normotensive subjects (r = 0.025; p = NS). Inadequate suppression of aldosterone in response to an increase in oral salt intake is related to LV structural and functional changes in hypertensive subjects. Thus, our results support experimental data indicating that aldosterone affects LV structure and function in humans and that this effect is BP independent.