Potassium excretion and blood pressure are associated with heart rate variability in healthy black adults: The African-PREDICT study.

BACKGROUND AND AIMS: Heart rate variability (HRV) is a main determinant of autonomic function and related to the development of hypertension and cardiovascular (CV) disease. Hypertension develops in black populations at an earlier age, which could be due to differences in the autonomic nervous system activity and sodium/potassium handling in black and white populations. We investigated whether HRV is associated with 24 h urinary sodium and potassium excretion and blood pressure (BP) in a young bi-ethnic cohort. METHODS AND RESULTS: We examined 423 black and 483 white healthy adults (aged 24.5 ± 3.1 years) for 24 h HRV, including standard deviation of normal RR intervals (SDNN) reflecting autonomic variations over time, and root mean square of successive differences (RMSSD) reflecting parasympathetic activity. We measured 24 h urinary sodium and potassium concentration and BP. The black group had lower SDNN and potassium excretion as well as higher RMSSD, sodium and Na/k ratio compared to the white group (all p < 0.05). Only in black individuals, urinary potassium excretion was independently and negatively associated with SDNN (ß[95% CI];-0.26[-0.50;-0.02]ms) and RMSSD (-0.14[-0.27;-0.01]ms, p < 0.05). One unit increase in sodium/potassium (Na/K) ratio was associated with higher SDNN (ß[95% CI]; 3.04[0.89; 5.19]ms) and RMSSD (1.60[0.41; 2.78]ms) in the black cohort only (both p < 0.001). In both groups elevated 24 h diastolic BP was associated with lower RMSSD (p < 0.05). CONCLUSION: Lower potassium excretion and higher Na/K ratio related independently to higher HRV in young and healthy black adults. A better ethnic-specific understanding of sodium and potassium handling is required as part of preventive cardiology, especially in black individuals. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT03292094; URL: https://clinicaltrials.gov/ct2/show/NCT03292094.

Graft function assessment in mouse models of single- and dual-kidney transplantation.

Animal models of kidney transplantation (KTX) are widely used in studying immune response of hosts to implanted grafts. Additionally, KTX can be used in generating kidney-specific knockout animal models by transplantation of kidneys from donors with global knockout of a gene to wild-type recipients or vice versa. Dual-kidney transplantation (DKT) provides a more physiological environment for recipients than single-kidney transplantation (SKT). However, DKT in mice is rare due to technical challenges. In this study, we successfully performed DKT in mice and compared the hemodynamic response and graft function with SKT. The surgical time, complications, and survival rate of DKT were not significantly different from SKT, where survival rates were above 85%. Mice with DKT showed less injury and quicker recovery with lower plasma creatinine (Pcr) and higher glomerular filtration rate (GFR) than SKT mice (Pcr = 0.34 and 0.17 mg/dl in DKT vs. 0.50 and 0.36 mg/dl in SKT at 1 and 3 days, respectively; GFR = 215 and 131 µl/min for DKT and SKT, respectively). In addition, the DKT exhibited better renal functional reserve and long-term outcome of renal graft function than SKT based on the response to acute volume expansion. In conclusion, we have successfully generated a mouse DKT model. The hemodynamic responses of DKT better mimic physiological situations with less kidney injury and better recovery than SKT because of reduced confounding factors such as single nephron hyperfiltration. We anticipate DKT in mice will provide an additional tool for evaluation of renal significance in physiology and disease.

Assessment of renal function in the anaesthetised rat following injection of superparamagnetic iron oxide nanoparticles.

A recent study showed that a significant fall in mean arterial pressure (MAP) occurred following intravenous injection of two novel superparamagnetic iron oxide nanoparticles (SPIONs), MF66 and OD15. To assess if this was caused by excessive glomerular clearance, the effect of both particles on renal function was studied. Experiments were performed on sodium pentobarbital anaesthetised male Wistar rats (250-350 g). Twenty-minute urine clearances were taken followed by an i.v. bolus of MF66, OD15 (2 mg·kg-1), or dH2O (0.4 mL·kg-1). MF6 or OD15 injection resulted in a significant transient drop in MAP and renal blood flow by approximately 33% and 50% (P < 0.05). The absolute excretion of sodium was significantly increased (P < 0.05) by almost 80% and 70% following OD15 and MF66, respectively. Similarly, fractional excretion of sodium was increased by almost 80% and 60% following OD15 and MF66, respectively. The glomerular filtration rate was not significantly affected, but urine flow increased nonsignificantly by approximately 50% and 66% following i.v. injection of OD15 and MF66, respectively. SPIONs produce a decrease in blood pressure and a natriuresis; however, the rate of fluid filtration in the kidney was not significantly affected.

[Effectiveness and adequacy of tolvaptan prescription in hospitalized patients]. / Efectividad y adecuación de la prescripción de tolvaptán en pacientes hospitalizados.

PURPOSE: To analyse the effectiveness of the use of Tolvaptan and the adequacy of Tolvaptan prescription at a tertiary level hospital. METHODS: Prospective observational study of Tolvaptan prescrip - tion from October of 2010 to December of 2011. RESULTS: 30 patients (60.0% males) were included, 50.0% of which were diagnosed with heart failure and 30.0% with SIADH. Tolvaptan allowed achieving sodium levels higher than 135 mEq/L in 53.3% of the patients with a mean baseline value of 125.3±7.3 mEq/L. The median treatment duration was 5.0 days (interquartile range=3-45). A significant increase of uric acid associated to Tolvaptan treatment was observed. The prescription was in agreement to what has been established in GFT in 63.3% of the cases. CONCLUSIONS: Tolvaptan increases sodium levels by 7.5 mEq/L, both in SIADH-associated hyponatremia and in heart failure, with an appropriate safety profile.

Objetivo: Analizar la efectividad del uso de tolvaptán y la adecuación de su prescripción en un hospital de tercer nivel. Método: Estudio observacional prospectivo de las prescripciones de tolvaptán desde octubre de 2010 hasta diciembre de 2011. Resultados: Se incluyeron 30 pacientes (60,0% varones), 50,0% diagnosticados de insuficiencia cardíaca y 30,0% de SIADH. Tolvaptán permitió alcanzar niveles de sodio superiores a 135 mEq/L en el 53,3% de los pacientes que partían con una media de 125,3±7,3 mEq/L. La mediana de días de tratamiento fue de 5,0 (rango intercuartílico = 3-45). Se observó un incremento significativo de los niveles de ácido úrico asociado al tratamiento con tolvaptán. La prescripción se adecuó a lo establecido en la GFT en el 63,3% de los casos. Conclusiones: Tolvaptán incrementa un 7,5 mEq/L los niveles de sodio tanto en hiponatremia secundaria al SIADH como en insuficiencia cardiaca.

Special focus on the role of α(1D)-adrenoreceptors in the assessment of renal tubular sodium re-absorptive responses in spontaneously hypertensive rats subjected to high sodium diet.

α(1D)-adrenoceptors are involved in the genesis/maintenance of hypertension in spontaneously hypertensive rats (SHR). This study aims to investigate the role of α(1D)-adrenoceptors in the antinatriuretic and antidiuretic responses in SHR subjected to high sodium (SHRHNa) and normal sodium (SHRNNa) intake for six weeks. Renal inulin clearance study was performed in which the antinatriuretic and antidiuretic responses to phenylephrine were examined in the presence and absence of α(1D)-adrenoceptors blocker BMY7378. Data, mean±S.E.M. were subjected to ANOVA with significance at p<0.05. Results show that feeding SHR for six weeks with high salt did not cause any change in blood pressure. SHRHNa had higher (all p<0.05) urine flow rate (UFR), fractional and absolute excretion of sodium (FE(Na) and U(Na)V) compared to SHRNNa. Phenylephrine infusion produced significant reduction in UFR, FE(Na) and U(Na)V in both SHRHNa and SHRNNa. The antidiuretic and antinatriuretic responses to phenylephrine in both groups were attenuated in the presence of BMY7378. Moreover, the antidiuretic and antinatriuretic responses to phenylephrine and BMY7378 were independent on any significant changes in renal and glomerular hemodynamics in both groups. Thus we conclude that high sodium intake did not bring any further increase in blood pressure of SHR, however, it results in exaggerated natriuresis and diuresis in SHRHNa. Irrespective of dietary sodium changes, α1-adrenoceptors are involved in mediating the antinatriuretic and antidiuretic responses to phenylephrine in SHR. Further, high sodium intake did not significantly influence the functionality of α(1D)-adrenoceptors in mediating the adrenergically induced antinatriuresis and antidiuresis.

Transjugular intrahepatic portosystemic shunt in the management of ascites and hepatorenal syndrome.

Ascites is the most common complication of liver cirrhosis and when it develops mortality is 50% at 5 years, apart from liver transplantation. Large volume paracentesis has been the only option for ascites refractory to medical treatment. The role of transjugular intrahepatic portosystemic shunt in the management of diuretic-resistant ascites has been evaluated in many cohort studies and five randomized trials up to now, clearly showing improvement in natriuresis and clinical efficacy. It, however, remains unclear how transjugular intrahepatic portosystemic shunt affects survival and quality of life, because hospital admissions owing to worsening encephalopathy may counterbalance the reduced need of paracentesis. What is clear is that the patient selection is critical. About 30% of patients with ascites develop hepatorenal syndrome at 5 years, leading to high mortality in its severe and progressive form. As its main pathogenetic factor is derangement of circulatory function owing to portal hypertension, these patients may benefit from transjugular intrahepatic portosystemic shunt, but this has been shown only in small series, in which mortality remains very high, owing to the underlying poor liver function.

Natriuretic effect of caffeine: assessment of segmental sodium reabsorption in humans.

In order to assess the intrarenal mechanisms responsible for the natriuretic action of caffeine, the renal clearances of (51)Cr-EDTA [used as a measure of glomerular filtration rate (GFR)] and lithium (used as an index of end-proximal fluid delivery) were measured in eight healthy males before (control period) and immediately after (experimental period) a 400 mg oral dose of caffeine (given over 90 min) or placebo. In caffeine-treated subjects, the fractional excretion of sodium rose from 1.00+/-0.25% in the control period to 1.47+/-0.18% in the experimental period, while corresponding values on the placebo day were 1.04+/-0.16% and 0.70+/-0.07% respectively. GFR was unchanged following either caffeine or placebo. When compared with the placebo day, caffeine caused increases in lithium clearance (experimental period values: caffeine, 37+/-1 ml/min; placebo, 28+/-2 ml/min; P <0.001), the fractional excretion of lithium (caffeine, 34+/-1%; placebo, 26+/-2%; P <0.001) and the sodium/lithium clearance ratio (used as an index of the fraction of sodium delivered to the distal nephron that escapes reabsorption therein: caffeine, 4.4+/-0.3%; placebo, 2.8+/-0.2%; P <0.001). These results suggest that reduced fractional sodium reabsorption in both the proximal tubule and the distal nephron contributes to the acute natriuretic effect of caffeine. The data also confirm the importance of controlling caffeine intake when investigating renal function using lithium clearance.

Re-assessment of the renal hydrosaline dysfunction in rats bearing the Walker-256 tumor.

Sodium retention is a frequent effect of cancer in humans and animals, but the mechanism involved is not yet understood. In the Walker-256 tumor, sodium retention has been considered to be a late effect, secondary to retention in the tumor mass, and/or to adrenal hypertrophy. Normally, (in rats receiving single tumor implants), the development of different tumor systemic effects (TSE) such as anorexia, sodium and fluid retention, anemia and immune depression in rats is synchronous within each individual but random among individuals of a given group in which they appear 6-47 days, or more, after inoculation. In present study, multifocal simultaneous inoculations of tumor cells resulted in a rapid and synchronous initiation of TSE (in 3-4 days) in all rats when no local effects of metastases could mask the results. Sodium retention is a special tumor effect on Na+ balance and a very sensitive indicator of TSE initiation. The results from multifocally inoculated rats were averaged in each (sub-clinical (SubC), moderate (mCP) and grave (gCP)) clinical phase and compared to food-restricted (FR) rats. There was a significant, early decrease in urinary Na+ excretion during mCP when compared to SubC and FR. The renal sites involved were studied in awake, unrestrained animals by measuring of sodium, creatinine and lithium clearances. There was an initial increase in the absolute proximal (mCP: 21.4 +/- 1.7 vs FR: 16.0 +/- 1.1 mmol/min/100 g b.w., p < 0.05) and post-proximal (mCP: 11.1 +/- 0.4 vs FR: 6.6 +/- 0.4 mmol/min/100 g b.w., p < 0.001) Na+ reabsorption, which were partially compensated for by a rise in glomerular filtration rate (mCP: 213 +/- 11.4 vs FR: 162 +/- 10.2 microL/min/100 g b.w., p < 0.01) and by a fall in fractional proximal Na+ reabsorption (mCP: 62.8 +/- 2.2% vs FR: 70.1 +/- 1.7%, p < 0.05), despite significant Na+ and fluid retention. The terminal phase of illness (gCP) culminated with a marked decrease in creatinine clearance, suggesting a significant fall in renal function. The multifocal model proved useful for studying the initial TSE, since the sites of action would, in principle, be easy to identify. These observations may be of physiological interest since TSE may result from the abnormal production of physiological modulators.

Renal adenosine A3 receptors in the rat: assessment of functional role.

The functional roles of adenosine A3 receptors in the rat kidney were assessed for the first time with respect to A1 receptor-mediated responses. Utilizing a chronically instrumented conscious rat preparation, we tested renal excretory responses to acute administration of the A3 receptor antagonists 3-ethyl-5-benzyl-2-methyl-6-phenyl-4-phenylethynyl-1 ,4-(+)-dihydropridine-3,5-dicarboxylate (MRS-1191) and 9-chloro-2-(2-furyl)-5-phenylacetylamino-[1,2,4]-triazolo[1,5-c]qu inazoline (MRS-1220) with reference to the effects of the A1 receptor antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX). The intravenous administration of DPCPX resulted in significant increases in fluid and sodium excretions without affecting glomerular filtration rate (GFR). This suggests that DPCPX-induced diuretic and natriuretic responses are related to decreased tubular reabsorption. However, neither MRS-1191 nor MRS-1220 alone affected fluid or sodium excretions, or GFR, indicating lack of an effect of either compound on renal function. On the other hand, the co-administration of MRS-1220 with DPCPX abolished both the diuretic and natriuretic responses to DPCPX, being suggestive of antagonism between these two compounds. MRS-1191, however, did not affect the DPCPX-induced fluid and sodium excretions. Neither the A1 nor the A3 receptor antagonists altered potassium excretion individually or in combination. The data suggest that while adenosine A1 receptors are involved in the regulation of renal fluid and sodium transport, A3 receptors do not appear to have a major role in regulation of renal excretory function under baseline physiological conditions.

Validity of a self-administered diet history questionnaire for assessment of sodium and potassium: comparison with single 24-hour urinary excretion.

We developed a self-administered diet history questionnaire (DHQ) for use in prevention and control of cardiovascular diseases and cancer, and validated it by comparison with single 24-h urinary excretion of sodium (Na) and potassium (K). The subjects were 154 male and 69 female freshmen university students. Mean intakes (mmol/day) assessed by DHQ and the urinary excretion of Na were 196 and 165 respectively for men and 179 and 136 respectively for women. Those of K were 61.5 and 43.9 respectively for men and 56.8 and 41.6 respectively for women. The ratios of urinary excretion to dietary intake of Na were 0.97 in men and 0.84 in women. Those of K were 0.78 in men and 0.80 in women. The results for both Na and K were reasonable, except for Na in men. When Pearson correlation was examined between dietary and urinary Na and K, no significant correlations for Na in men (r=0.14) or women (r=0.23, p=0.06), or significant correlations for K in men (r=0.34, p<0.001) or women (r=0.40, p<0.001) were observed. The results suggest a reasonable ability to estimate a subject mean for Na in women, K in both sexes, and individual level for K for both sexes. The validity for individual level for Na intake is not conclusive because the duration of urine collection was too short.

Urinary cortisol metabolites in the assessment of peripheral thyroid hormone action: overt and subclinical hypothyroidism.

UNLABELLED: Biological assessment of peripheral thyroid hormone action may be important in subclinical hypothyroidism, where decision-making is often difficult. The impairment of urinary cortisol metabolites in overt hypothyroidism reflects an acquired 11 beta hydroxysteroid dehydrogenase (11 beta OHSD) deficiency, and is assessed in terms of a reduction in the tetrahydrocortisone (THE)/tetrahydrocortisol (THF) ratio or THE/THE + alpha THF ratio; the alpha THF/THF ratio reflects 5 beta reductase activity. The aim of this study was to determine if urinary cortisol metabolite ratios are a good index of peripheral thyroid hormone action in subclinical hypothyroidism. MATERIALS AND METHODS: the THE/THF, THE/THF + alpha THF and alpha THF/THF ratios were measured in 24 h urine samples from 3 groups of subjects: 1) 18 euthyroid subjects; 2) 25 patients with elevated serum TSH and low FT4 levels (overt hypothyroidism); and 3) 25 patients with increased serum TSH and normal FT4 levels (subclinical hypothyroidism. RESULTS: 7/25 overtly and 5/25 subclinically hypothyroid patients had a THE/THF + alpha THF ratio below the mean control value -2 SD, while respectively 20/25 and 11/25 patients had a THE/THF ratio below the mean control value -2 SD. The mean THE/THF + alpha THF, THE/THF and alpha THF/THF ratios were significantly different among the 3 groups (ANOVA) and were lower in the overtly hypothyroid group than in the other two groups (Fisher's test); daily urine sodium output was also significantly different between the three groups and lower in the overtly and subclinically hypothyroid groups than in the control group (Fisher's test). FT3 and FT4 both correlated with THE/THF + alpha THF in the overtly hypothyroid patients (r = 0.43; p < 0.05 and r = 0.40; p < 0.05, respectively). In the subclinically hypothyroid patients, TSH correlated with THE/THF + alpha THF (r = 0.44; p < 0.05) and THE/THF (r = 0.43; p < 0.05). FT3, FT4 and TSH levels correlated with THE/THF + alpha THF (p < 0.001), THE/THF (p < 0.001), alpha THF/THF (p < 0.001) and daily natriuresis (p < 0.05) in the whole population (patients + controls). In conclusion, urinary cortisol metabolites, although impaired in overt hypothyroidism, are not an accurate index of peripheral thyroid hormone deficiency in subclinical hypothyroidism. We also identified an increase in the alpha THF/THF ratio in overt hypothyroidism, which may be related to 5 beta reductase disturbances.

Indirect assessment of glomerular capillary pressure from pressure-natriuresis relationship: comparison with direct measurements reported in rats.

It is examined whether glomerular hemodynamics can be indirectly estimated from the pressure-natriuresis relationship. There are only two animal studies reported, one in normal and the other in 5/6 nephrectomized Munick-Wistar rats, which permits plotting the pressure-natriuresis relationship and comparison of indirect estimations with directly measured glomerular hemodynamic data. Normal and extensive renal ablation rats were placed on relatively high and low sodium diets. Plotting mean arterial pressure (MAP) on the x-axis and 24 h urinary sodium excretion rate on the y-axis, the pressure-natriuresis relationship was drawn. As the difference between MAP (121 +/- 1 and 169 +/- 12 mmHg) on relatively high sodium diet and the extrapolated x-intercept (122 and 138 mmHg) of the pressure-natriuresis relationship, based on previous proposal, the effective filtration pressure across the glomerular capillary walls was estimated to be-1 and 31 mmHg for normal and 5/6 nephrectomized rats. Then, the glomerular capillary hydraulic pressure (PGC) was calculated to be 33 and 64 mmHg. Micropuncture studies showed that directly measured PGC of 47 +/- 1 and 65 +/- 2 mmHg was close agreement with those estimated indirectly. Therefore, an approach from the pressure-natriuresis relationship provides a noninvasive means to predict an approximation of PGC. This approach to estimating glomerular hemodynamics may have invaluable implications for clinical practice; in the early detection of loss of filtration capacity and in the assessment of an important risk factor for the development of chronic renal failure.

A micropuncture study of the renal response to haemorrhage in rats: assessment of the role of vasopressin.

The acute effects of haemorrhage (15 ml (kg body wt)-1) on renal function at whole-kidney and single-nephron levels were studied in Inactin-anaesthetized rats. In order to assess the role of vasopressin in mediating the haemodynamic effects, responses in untreated Long-Evans rats were compared with those in Brattleboro rats (which lack circulating vasopressin) and in Long-Evans rats treated with a V1 receptor antagonist. In time-control animals, there were no significant changes in mean arterial pressure (MAP), excretion rates, glomerular filtration rate (GFR), superficial-nephron GFR (SNGFR) or fluid reabsorption in the superficial proximal tubules during the course of the experiment. Following haemorrhage, the immediate reduction in MAP was followed in each group by partial recovery for 30 min; thereafter, MAP was stable. In untreated Long-Evans rats, haemorrhage was followed by a 26% reduction in GFR (P < 0.001, measured 60-150 min post-haemorrhage) and a larger reduction (45%, P < 0.001) in SNGFR, so that the SNGFR/GFR ratio fell significantly ((27.9 +/- 1.9) x 10(-6), control period; (20.2 +/- 2.2) x 10(-6) post-haemorrhage, P < 0.01). Slightly greater reductions in GFR and SNGFR were seen in Brattleboro rats and V1 antagonist-treated Long-Evans rats, which corresponded to slightly greater haemorrhage-induced reductions in blood pressure in these groups; the falls in the SNGFR/GFR ratio were similar to that in untreated Long-Evans rats. In all three groups of bled rats, fractional reabsorption by the proximal convoluted tubule increased slightly 30-60 min after haemorrhage, but during the subsequent period (60-150 min) returned to values indistinguishable from those during the control period. The results suggest that the renal haemodynamic changes that follow moderate haemorrhage include a preferential reduction in the GFR of superficial nephrons. Vasopressin appears to play no role in this response. Increases in fractional reabsorption in the proximal tubules are seen only during the immediate post-haemorrhage period.

Transjugular intrahepatic portosystemic shunts for refractory ascites: assessment of clinical and hormonal response and renal function.

Cirrhosis is frequently complicated by ascites that may become resistant to diuretic therapy. Transjugular intrahepatic portosystemic shunts (TIPS) represent a new treatment for this debilitating condition. The aim of this study was to ascertain the clinical efficacy of TIPS, as well as its impact on renal function and on hormonal parameters. Five inpatients with refractory ascites were studied prospectively before TIPS, and 3 and 14 days after TIPS. After TIPS, ascites completely resolved or was minimal in all patients. Diuretics were discontinued in three subjects and decreased by at least 50% in two. One patient developed liver failure after TIPS and required liver transplantation; the others remained stable after a mean follow-up of 14 months. Mean urinary sodium excretion increased from 2.1 +/- 0.6 mEq/24 hr before TIPS to 13.0 +/- 4.3 mEq/24 hr 14 days after TIPS. Mean serum creatinine and glomerular filtration rate also tended to improve during the study period. With the exception of the patient who developed liver failure, plasma aldosterone concentration decreased from a mean of 126.0 +/- 29.9 ng/dL to 22.8 +/- 6.8 ng/dL (P = .04), and plasma renin activity decreased from a mean of 9.0 +/- 3.0 micrograms/L/h to 0.9 +/- 0.1 microgram/L/h (P = .08). Additionally, 19 patients who underwent TIPS for refractory ascites outside of this protocol were followed prospectively for a mean of 282 days. Clinical improvement in ascites control was noted in 74%, and the mean dose of diuretics was decreased by more than 50%. Nonresponders more often had underlying renal disease. In conclusion, TIPS is an effective therapy for refractory ascites in most patients.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of two tests for the assessment of blood pressure responses to sodium.

In order to assess the congruity of two different methods for the characterization of blood pressure responsivity to alterations in sodium and extracellular fluid volume balance, we studied 40 normotensive and hypertensive humans. All subjects were initially studied with a protocol of rapid sodium and volume expansion induced by intravenous administration of 0.9% saline (2 L over 4 h) followed by a day of sodium and volume depletion achieved by a low (10 mmol) sodium diet and three 40 mg oral doses of furosemide. Subsequently the subjects underwent a dietary protocol consisting of 5 days of a high (> or = 200 mmol/da) sodium diet followed by 7 days of a low (< or = 15 mmol/day) sodium diet. Blood pressure measurements as well as urinary sodium, potassium, and creatinine excretion measurements were made daily in both studies. A significant (P < .01) correlation was observed between the blood pressure responses to the separate techniques in the same individual. However, not all subjects responded in a similar qualitative fashion to the two maneuvers. The discrepancy was more frequent among subjects having a salt-resistant response to the rapid protocol. The renin response to sodium and volume depletion induced by the low sodium diet and furosemide correlated significantly (P < .001) with the subsequent blood pressure response to the low sodium diet. Subjects defined as salt-sensitive differed from the salt-resistant group by more sluggish renal adaptation to dietary sodium restriction. These findings demonstrate the congruity of two different approaches for the assessment of salt responsivity of blood pressure in humans.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of atrial natriuretic peptide resistance in cirrhosis with head-out water immersion and atrial natriuretic peptide infusion.

The nature of sodium retention in cirrhosis complicated by ascites has been studied for the last 30 years. Resistance to the natriuretic action of atrial natriuretic peptide (ANP) may play a potential role in this sodium retention. To further evaluate this possibility, we studied 12 patients with biopsy-proven cirrhosis and ascites on 2 consecutive days after a 7-day period off diuretics while receiving a 20 mmol/day sodium restricted diet. Following a crossover design, patients underwent head-out water immersion (HWI) for 3 h and were infused with a alpha-human ANP for 2 h on 2 consecutive days. Blood and urine samples were collected hourly. Five patients displayed a natriuretic response to HWI, sufficient to achieve negative sodium balance, and these patients were termed responders. Each of these five patients also displayed a natriuretic response to ANP infusion. In contrast, the other seven patients (nonresponders) consistently failed to develop a natriuretic response to either maneuver. The two groups had similar elevations in plasma ANP concentrations, but at baseline differed in terms of plasma sodium, plasma renin activity, and serum aldosterone. Despite higher serum aldosterone concentrations, nonresponders excreted less potassium than responders during the peak effect of the interventions, suggesting greater sodium delivery to the aldosterone-sensitive nephron segment in responders. We conclude that the inability to mount an adequate sodium excretory response to HWI in patients with cirrhosis may be conveyed through increased antinatriuretic factors that decrease the sodium delivery to the medullary collecting duct and inhibit the natriuretic effect of ANP at that site.