Intracellular Sodium Levels Research Articles

Release mechanisms of [125I]meta-iodobenzylguanidine in neuroblastoma cells: evidence of a carrier-mediated efflux.

[131I]metaiodobenzylguanidine ([131I]MIBG) is selectively taken up and stored by tumours derived from the neural crest, and is used for diagnosis and treatment of neuroblastoma (NB). The antitumoral effect of [131I]MIBG is closely related to the intracellular level of the radiopharmaceutical compound, which is dependent on uptake and storage/release mechanisms. While MIBG uptake is well characterised, storage and release mechanisms are still controversial. In order to better characterise [125I]MIBG release mechanisms, we studied the basal and stimulated efflux of [125I]MIBG in the human NB cell line, SH-SY5Y, preloaded with 0.1 microM [125I]MIBG for 1 h. We found that [125I]MIBG basal efflux is highly temperature-dependent, that [125I]MIBG release, induced by cell depolarisation with high potassium, is mainly calcium-independent, and induced by exchange with cold MIBG or noradrenaline, inversion of the sodium gradient across the cell membrane by veratridine by substitution of sodium chloride with equimolar concentration of lithium chloride. The exposure of NB cells to imipramine, an Uptake-1 inhibitor, also produces a net stimulatory effect on [125I]MIBG release. However, when used in association with other releasing stimuli, such as higher levels of intracellular sodium or external agonists, imipramine abolishes the consequent increase of [125I]MIBG release. Our findings suggest that stimulated [125I]MIBG release is mediated by a carrier, most probably the uptake carrier working in a reverse mode, while a minimal fraction of [125I]MIBG is released by an exocytotic mechanism.

Univalent Cation Fluxes in Human Erythrocytes from Individuals with Low or Normal Sodium Intake

High salt intake is a risk factor for essential hypertension in man. There is evidence that, in hypertension, intracellular sodium content and univalent cation transport across erythrocyte membranes are changed. It has been proposed that a low-sodium diet has an antihypertensive effect; this may be related to changes in cation fluxes across plasma membranes. Sodium and potassium fluxes and the composition of fatty acids were studied in the erythrocytes of people who had eaten a low-sodium vegan diet for many years (n = 9) and in those of controls who had consumed a mixed diet (n = 11) to investigate the dependence of these variables on dietary factors. Both systolic and diastolic blood pressures were lower in vegans than in controls. The passive permeability to sodium (P < 0.05) ,Na+,K+ cotransport (P < .001) and the intracellular content of exchangeable sodium (P = 0.076) were decreased in the erythrocytes of those who had consumed the low-sodium diet compared with the controls. The activity of the Na+-K+ pump, Na+-H+ exchange and the passive permeability to potassium were unaltered. Swelling-induced K+,C1- cotransport was increased in the erythrocytes of those who had eaten the low-sodium vegan diet compared with controls (P < 0.01). The proportion of linoleic acid was increased (P < 0.01) at the expense of eicosapentaenoic and docosahexaenoic acids (P < 0.001) in the erythrocyte membranes of the vegans. Our results show that levels of intracellular sodium and Na+,K+ cotransport activity, which increase in patients with hypertension, decreased in those consuming a low-sodium vegan diet. This suggests that the risk of essential hypertension was diminished in the vegan participants, confirming our observation that systolic and diastolic blood pressures were lower in the strict vegans than in the controls.

Double-quantum-filtered 23Na NMR study of intracellular sodium in the perfused liver

We acquired double-quantum-filtered 23Na NMR spectra from perfused liver, using a range of tau values from 0.2 to 24 ms, where tau is the separation between the first and second pi/2 pulses in the radio-frequency pulse sequence. For each tau value we compared the amplitude of the double-quantum-filtered 23Na NMR signal acquired from intracellular sodium ions when the liver was perfused with buffer containing the "shift reagent" Dy(PPP)2 to the amplitude of the total double-quantum-filtered 23Na NMR signal acquired when the liver was perfused with buffer containing no Dy(PPP)2. For tau < or = 4 ms, the average ratio of the two amplitudes was 0.98 +/- 0.03 (mean +/- SEM). For tau > or = 8 ms, the average ratio was significantly less than 1. These results demonstrate that double-quantum-filtered 23Na NMR signals acquired from perfused liver using short tau values arise almost exclusively from intracellular sodium ions, but double-quantum-filtered 23Na NMR signals acquired from perfused liver using long tau values contain contributions from both intracellular and extracellular sodium ions. This conclusion suggests that multiple-quantum-filtered 23Na NMR spectroscopy will be useful in studying intracellular sodium levels in the perfused liver, and possibly in the intact liver in vivo.

Nuclear magnetic resonance measurement of intracellular sodium in the perfused normotensive and spontaneously hypertensive rat heart.

We have used 23Na nuclear magnetic resonance spectroscopy to examine the relationship between intracellular sodium and cardiac muscle alterations in genetic hypertension. In the spontaneously hypertensive rat (SHR) compared with the normotensive Wistar-Kyoto rat (WKY) (aged 15 to 19 weeks), mean systolic blood pressures (measured using the tail-cuff method) were significantly (P < .05) different (WKY: 118 +/- 8 mm Hg, n = 5; SHR: 185 +/- 9 mm Hg, n = 5). Heart weights were also increased significantly (P < .05) in SHR (grams dry heart to kilograms body weight ratio was 0.73 +/- 0.04, n = 5, for SHR and 0.55 +/- 0.02, n = 5, for WKY). Intracellular sodium levels, measured using shift-reagent-aided and triple quantum filtered (TQF) nuclear magnetic resonance techniques, were significantly increased (P < .05) in the isolated Langendorff perfused hypertensive rat hearts (17.3 +/- 3.6 mmol/L, n = 5) compared with normotensive rat hearts (8.4 +/- 2.3 mmol/L, n = 5). These data demonstrate increased sodium in cardiac muscle in essential hypertension. We also investigated the effect of pacing on cardiac TQF 23Na nuclear magnetic resonance and found an increase in TQF Na+ content in both WKY and SHR hearts on stepped up pacing. These results support the existence of sodium pump lag in the rat heart perfused at physiologic Ca2+ concentration and suggest that the hypertensive rat heart has adapted to compensate for increased basal intracellular Na+ and maintain a normal response to increased heart rate. Our data appear to suggest an ionic contribution to the cardiac hypertrophy of genetic hypertension in the rat.

Method for Determination of Intracellular Sodium in Perfused Cancer Cells by 23Na Nuclear Magnetic Resonance Spectroscopy

Changes of intracellular sodium concentrations are often an indication of disease or malfunction. In this work, shift reagent-aided 23Na NMR spectroscopic determination of intracellular sodium was adapted to measurements with perfused cells embedded in agarose gel threads. Ehrlich ascites tumor cells (EHR2) and their multidrug-resistant counterparts (EHR2/DNR+) were immobilized and perfused until the metabolic steady state had been reached as shown by 31P NMR spectroscopy. Subsequent addition of 5 mM dysprosium(III) bis(tripolyphosphate) to the perfusion medium caused a separation of extracellular and intracellular 23Na NMR signals, making quantification of the intracellular sodium possible. The dysprosium shift reagent was apparently nontoxic to the cells, as shown by the unchanged level of ATP and other intracellular phosphates. NMR visibility of the intracellular sodium was determined in suspensions of EHR2 and EHR2/DNR+ cells by treatment with digitonin; the increase of intensity of the extracellular sodium resonance observed after the digitonin treatment corresponded well (97 ± 3%) to the sum of intracellular and extracellular sodium observed with intact cells prior to the digitonin treatment. The resistant EHR2/DNR+ cells contained a moderately higher intracellular sodium level than the wild-type EHR2 cells, 1.02 ± 0.10 and 0.77 ± 0.07 μmol Na/mg protein, respectively. Closely similar levels of intracellular sodium were found by flame photometry. Thus, 23Na NMR offers a reliable method for noninvasive quantification of intracellular sodium in perfused cancer cells.

Intracellular free sodium concentrations in GH4C1 cells.

In the present investigation, intracellular sodium ([Na+]i) levels were determined in GH4C1 cells using the fluorescent probe SBFI. Fluorescence was determined by excitation at 340 nm and 385 nm, and emission was measured at 500 nm. Intracellular free sodium ([Na+]i) was determined by comparing the ratio 340/385 to a calibration curve. The ratio was linear between 10 and 60 mM Na+. Resting [Na+]i in GH4C1 cells was 26 +/- 6.2 mM (mean +/- SD). In cells incubated in Na(+)-free buffer [Na+]i decreased to 3 +/- 3.6 mM. If Na+/K+ ATPase was inhibited by incubating the cells with 1 mM ouabain, [Na+]i increased to 47 +/- 12.8 mM in 15 min. Stimulating the cells with TRH, phorbol myristyl acetate, or thapsigargin had no effect on [Na+]i. Incubating the cells in Ca(2+)-free buffer rapidly increased [Na+]i. The increase was not inhibited by tetrodotoxin. Addition of extracellular Ca2+, nimodipine, or Ni2+ to these cells immediately decreased [Na+]i, whereas Bay K 8644 enhanced the influx of Na+. In cells where [Na+]i was increased the TRH-induced increase in intracellular free calcium ([Ca2+]i) was decreased compared with control cells. Our results suggest that Na+ enters the cells via Ca2+ channels, and [Na+]i may attenuate TRH-induced changes in [Ca2+]i in GH4C1 cells.

Decreased erythrocyte Na +, K +-ATPase activity associated with cellular potassium loss in extremely low birth weight infants with nonoliguric hyperkalemia

To determine whether a shift of potassium ions from the intracellular space to the extracellular space accounts, in part, for the hyperkalemia seen in extremely low birth weight infants, we examined potassium concentration in serum and erythrocytes from extremely low birth weight infants with hyperkalemia (n = 12) or with normokalemia (n = 27). In addition, to determine whether the shift of potassium was associated with low sodium-potassium-adenosinetriphosphatase (Na+,K(+)-ATPase) activity, we studied the activity of ATPase in the last 16 infants enrolled in the study. Fluid intake and output were measured during the first 3 days of life. Infants were considered to have hyperkalemia if the serum potassium concentration was 6.8 mmol/L or greater. Blood was obtained daily for intracellular sodium and potassium levels by means of lysis of erythrocytes. The remaining erythrocyte membranes were frozen and analyzed for Na+,K(+)-ATPase activity. There were significantly lower intracellular potassium/serum potassium ratios in the infants with hyperkalemia for each day of the 3-day study (p < 0.001). In the hyperkalemic group, there was lower Na+,K(+)-ATPase activity than in the infants with normokalemia (p = 0.006). Low Na+,K(+)-ATPase activity was associated with lower intracellular potassium/serum potassium ratios (p = 0.006), higher serum potassium values (p = 0.02), and lower intracellular potassium concentration (p = 0.009). The urinary data demonstrated that there was no difference in glomerulotubular balance between the two groups. We conclude that nonoliguric hyperkalemia in extremely low birth weight infants may be due, in part, to a shift of potassium from the intracellular space to the extracellular space associated with a decrease in Na+,K(+)-ATPase activity.

Improvement of spectral resolution in shift‐reagent‐aided 23Na NMR spectroscopy in the isolated perfused rat heart system

The level of intracellular sodium (Nai) is maintained at approximately 14 mM in healthy myocytes. When myocytes are damaged, Nai increases and therefore the level of Nai may be a means of evaluating myocardial cell integrity. A particularly useful method to monitor Nai levels is 23Na NMR spectroscopy. However, because of the isochronous nature of the extracellular sodium (Nao) and Nai NMR signals, paramagnetic lanthanide shift reagents (LSR), such as dysprosium triphosphate, Dy(PPP)7-(2), have been used to shift the Nao signal. This reveals the unshifted Nai signal and allows the NMR monitoring of Nai in isolated perfused hearts and other systems. A major shortcoming of this method (the "shift-only" method) is in the need to minimize the Nao signal by not submerging the perfused hearts in Na(+)-containing buffer. An equally undesirable alternative is the utilization of relatively high concentrations of LSR to shift a large Nao signal sufficiently to enable reasonable resolution and quantitation of Nai. We present here a method, the "shift-relaxation" method, which is a combination of using a mixture of Dy(PPP)7-(2), a shift reagent, and gadolinium triphosphate, Gd(PPP)7-(2), a relaxation agent, with data acquisition using an inversion-recovery (IR) pulse sequence. This combination allows differentiation between Nao and Nai by the difference in their respective T1 values in addition to the shift between them. With this technique we can selectively minimize the extracellular signal and therefore minimize the need for a large Dy-induced shift, as well as allow data acquisition on a heart submerged in Na(+)-containing perfusate. The resulting improved discrimination between Nai and Nao at relatively low levels of LSR should be helpful for ultimate in vivo applications and potential clinical applications, where a lower dose of LSR also means a decreased possibility of physiologically deleterious effects. Also included in this paper is a method for the quick determination of an accurate 180 degrees pulse which is required for the optimization of the IR method.

Local Myocardial Biochemical and Ionic Alterations During Myocardial Ischaemia and Reperfusion

Acute myocardial ischaemia and reperfusion result in a series of inhomogeneous metabolic, ionic and neurohumoral events that explain the associated mechanical and electrical events, including cardiac death. The time course of the hydrolysis of high energy phosphates, the rise in extracellular potassium and the fall in intracellular and extracellular pH induced by acute no-flow ischaemia have been well characterised. However, the time course of the changes in intracellular sodium, calcium and magnesium levels is less clear. It appears that the changes in intracellular calcium may be pivotal to many of the biochemical and electrophysiological changes produced by the abrupt cessation of coronary arterial inflow and the associated interruption of venous washout. Consequently, agents that modify the handling of calcium by the sarcolemma and the sarcoplasmic reticulum have a significant impact on many of the metabolic, ionic and electrical abnormalities characterising acute ischaemia and reperfusion.

A review of 23Na nuclear magnetic resonance spectroscopy for the in vitro study of cellular sodium metabolism

Changes in intracellular sodium have been associated with a number of different diseases. Consequently, various methods have been used to quantify the level of intracellular sodium concentrations. Traditional methods like flame photometry and ion-selective electrodes are destructive or invasive, thereby potentially altering the intracellular sodium levels. There has been an increasing interest in evaluating the method of 23Na nuclear magnetic resonance in recent years, since this method allows for non-invasive continuous monitoring of intracellular sodium in cell suspensions and tissues. A phenomenological approach to basic theory, review of methodology, applications to the in vitro study of cellular sodium metabolism, and difficulties of interpretation of this analytical modality is presented.

A review of23Na nuclear magnetic resonance spectroscopy for thein vitrostudy of cellular sodium metabolism

Changes in intracellular sodium have been associated with a number of different diseases. Consequently, various methods have been used to quantify the level of intracellular sodium concentrations. Traditional methods like flame photometry and ion-selective electrodes are destructive or invasive, thereby potentially altering the intracellular sodium levels. There has been an increasing interest in evaluating the method of 23Na nuclear magnetic resonance in recent years, since this method allows for non-invasive continuous monitoring of intracellular sodium in cell suspensions and tissues. A phenomenological approach to basic theory, review of methodology, applications to the in vitro study of cellular sodium metabolism, and difficulties of interpretation of this analytical modality is presented.

Erythrocyte cation metabolism in preeclampsia

To determine if there are abnormalities in cellular cation regulation in pregnancy-induced hypertension, erythrocyte intracellular levels of calcium, magnesium, sodium, and potassium and circulating parathyroid hormone and "endoxin" were examined in 13 women with pregnancy-induced hypertension and 34 control subjects matched for gestational age (greater than or equal to 35 weeks). Both endoxin and parathyroid hormone levels were higher in patients with pregnancy-induced hypertension than in control subjects (endoxin, 294 +/- 34 vs. 210 +/- 19 pg/ml, p less than 0.05; parathyroid hormone, 0.65 +/- 0.05 vs. 0.60 +/- 0.03 ng/ml); the increase was significant only for endoxin. Intracellular calcium was higher in the patients with pregnancy-induced hypertension (0.033 +/- 0.010 vs. 0.015 +/- 0.001 mEq/L, p less than 0.05, in the patients with pregnancy-induced hypertension and control patients, respectively) but intracellular sodium, potassium, and magnesium levels were not different. This intracellular calcium elevation may be caused directly by the increase in parathyroid hormone or indirectly by the observed elevation in endoxin. Our data indicate that the observed effect is specific because no changes in intracellular sodium, potassium, or magnesium levels were found.

Intracellular sodium, potassium and high energy phosphate levels in the myocardium during ischemia: Studies with 23Na-, 39K- and 31P-NMR : T. Ishibashi, T. Matsubara, M. Nakazawa and S. Imai. Department of Pharmacology, Niigata University School of Medicine, Niigata, Japan

Intracellular sodium, potassium and high energy phosphate levels in the myocardium during ischemia: Studies with 23Na-, 39K- and 31P-NMR : T. Ishibashi, T. Matsubara, M. Nakazawa and S. Imai. Department of Pharmacology, Niigata University School of Medicine, Niigata, Japan

Effects of muscarinic, alpha-adrenergic, and substance P agonists and ionomycin on ion transport mechanisms in the rat parotid acinar cell. The dependence of ion transport on intracellular calcium.

The relationship between receptor-mediated increases in the intracellular free calcium concentration [( Ca]i) and the stimulation of ion fluxes involved in fluid secretion was examined in the rat parotid acinar cell. Agonist-induced increases in [Ca]i caused the rapid net loss of up to 50-60% of the total content of intracellular chloride (Cli) and potassium (Ki), which is consistent with the activation of calcium-sensitive chloride and potassium channels. These ion movements were accompanied by a 25% reduction in the intracellular volume. The relative magnitudes of the losses of Ki and the net potassium fluxes promoted by carbachol (a muscarinic agonist), phenylephrine (an alpha-adrenergic agonist), and substance P were very similar to their characteristic effects on elevating [Ca]i. Carbachol stimulated the loss of Ki through multiple efflux pathways, including the large-conductance Ca-activated K channel. Carbachol and substance P increased the levels of intracellular sodium (Nai) to more than 2.5 times the normal level by stimulating the net uptake of sodium through multiple pathways; Na-K-2Cl cotransport accounted for greater than 50% of the influx, and approximately 20% was via Na-H exchange, which led to a net alkalinization of the cells. Ionomycin stimulated similar fluxes through these two pathways, but also promoted sodium influx through an additional pathway which was nearly equivalent in magnitude to the combined uptake through the other two pathways. The carbachol-induced increase in Nai and decrease in Ki stimulated the activity of the sodium pump, measured by the ouabain-sensitive rate of oxygen consumption, to nearly maximal levels. In the absence of extracellular calcium or in cells loaded with the calcium chelator BAPTA (bis[o-aminophenoxy]ethane-N,N,N',N'-tetraacetic acid) the magnitudes of agonist- or ionomycin-stimulated ion fluxes were greatly reduced. The parotid cells displayed a marked desensitization to substance P; within 10 min the elevation of [Ca]i and alterations in Ki, Nai, and cell volume spontaneously returned to near baseline levels. In addition to quantitating the activation of various ion flux pathways in the rat parotid acinar cell, these results demonstrate that the activation of ion transport systems responsible for fluid secretion in this tissue is closely linked to the elevation of [Ca]i.

High plasma levels of a ouabain‐like factor in normal pregnancy and in pre‐eclampsia*

Recent reports have described high levels of one or more substances which cross-react with digoxin antibodies in the serum of women with pre-eclampsia. We measured plasma ouabain-like activity and intraerythrocyte sodium and potassium concentrations, in addition to performing routine hypertensive laboratory tests, in 13 normotensive non-pregnant subjects, 15 normotensive pregnant women and 16 pre-eclamptic women (gestational age: 33-36 weeks). Plasma ouabain-like activity, measured as plasma-induced variations in ouabain binding to human erythrocytes, proved significantly higher in both groups of pregnant subjects as compared to normotensive non-pregnant women, and a significant difference was also found between pre-eclamptic and normotensive pregnant women, the former exhibiting higher plasma ouabain-like activity. No differences in intracellular sodium and potassium levels were detected among the three groups studied. Though there is reason to believe that the high plasma levels found both in normal and hypertensive pregnancy may depend on placental production, we are not in a position to define with any degree of certainty what the mechanism or mechanisms are that regulate ouabain-like factor production.

Synthetic Diacylglycerols Trigger an Increase of Intracellular Free Calcium in Promyelocytic HL60 Cells

Phosphoinositide turnover is known to play an important role in intracellular free calcium homeostasis through the inositol trisphophate-mediated release of calcium from intracellular stores. We find that the other product of phosphoinositide turnover, 1,2-diacylglycerol, elicits an increase in intracellular free calcium in HL60 cells which is due, at least in part, to release of calcium from intracellular stores. This effect is specific for calcium, since intracellular sodium and potassium levels and cellular volume were unaffected. Concomitant with the intracellular calcium increase, we find an increase in cellular inositol trisphosphate levels, suggesting that the effect of diacylglycerol on calcium may be mediated by inositol trisphosphate. Diacylglycerols also stimulate calcium efflux. This stimulation is not simply due to the increase in intracellular calcium. These effects appear not to be mediated through stimulation of a phorbol ester-activatable protein kinase C (Ca2+/phospholipid-dependent enzyme) since phorbol esters do not elicit an increase in cytoplasmic free calcium or an increase in calcium efflux.

Developmental changes in reperfusion injury: Comparison of intracellular ion accumulation in ischemic and cardioplegic arrest

Developmental differences in ischemic and potassium cardioplegic arrest were evaluated in newborn (birth to 7 day old) and adult (6 to 12 month old) New Zealand white rabbit hearts isolated and perfused by Langendorff's method. An extracellular space washout technique was used to measure intracellular sodium and calcium in the two age groups after ischemia alone, after normothermic and hypothermic cardioplegia, and after cardioplegia with reperfusion. Although the intracellular ionic contents of nonreperfused adult hearts after 30 and 40 minutes of ischemia were identical, there was a twofold elevation in intracellular sodium level after 40 minutes of ischemia in the newborn hearts. Adult hearts arrested by normothermic potassium cardioplegia demonstrated no alteration in the intracellular ionic content, whereas in the newborn hearts, potassium cardioplegia produced excess intracellular calcium loading before reperfusion, which was greater than that occurring with ischemia alone. When hypothermia (12 degrees C) was combined with cardioplegic arrest, a prereperfusion influx of sodium and calcium was not observed in the newborn hearts, and ionic reperfusion injury was blunted in both newborn and adult hearts. These studies demonstrate that the newborn heart is more susceptible than the adult to both ischemia and cardioplegia. This may be due to age-dependent differences in transmembrane passive diffusion, sodium/calcium exchange, or calcium slow channel properties and suggests alternative myocardial protective strategies for the newborn infant.

A digoxin-like factor associates with erythrocyte sodium concentration, sodium transport, and ouabain binding

To investigate what effects a circulating digoxin-like factor (DLF) might have on sodium metabolism, we examined data collected on 1,327 individuals screened in the Cardiovascular Genetics Clinic at the University of Utah. This sample included 639 unmedicated adults, 582 youths under age 18, and 106 medicated hypertensive individuals, all on an unrestricted diet when attending clinic. No individuals took digitalis. A digoxin assay detected measurable levels of plasma DLF in 13.4% of the youths, 17.2% of the normotensive adults, and 25.5% of the hypertensive adults. In all three groups of individuals, those with a measurable DLF had a significantly lower erythrocyte ouabain sensitive sodium efflux rate constant (adjusted for age, sex and body mass) than those with no measurable DLF ( p < 0.01). Normotensive and hypertensive adults with measurable DLF also had an increased erythrocyte intracellular sodium level. Either the number of ouabain binding sites and/or the apparent affinity for ouabain were reduced for those with DLF levels in all three groups. There was a small nonsignificant increase in blood pressure for the normotensive adults and youths with a measurable DLF. We conclude that plasma DLF is associated with reduced ouabain sensitive sodium transport and increased intracellular sodium concentration, possibly due to changes in the number of or the competition for the Na +  K + ATPase sites.

Temporal relationship of hepatocellular dysfunction and ischemia in sepsis.

To determine whether hepatic dysfunction in sepsis results from hypoperfusion or direct cellular injury, Sprague-Dawley rats underwent either cecal ligation and puncture or sham operation. After either two or six hours, effective hepatic blood flow was measured using the galactose clearance method. Hepatocytes were isolated and intracellular sodium and potassium and glucose production were measured. Hepatic blood flow in septic rats decreased as early as two hours after sepsis when compared with sham-operated rats (3.8 +/- 1.4 vs 8.7 +/- 3.1 mL/min/100 g body weight). Intracellular sodium and potassium levels and glucose production in septic rats were not significantly different when compared with controls at two hours. After six hours, hepatic blood flow remained depressed and intracellular sodium level was increased compared with sham-operated rats (41.7 +/- 10.4 vs 31.4 +/- 5.9 mmol/L [41.7 +/- 10.4 vs 31.4 +/- 5.9 mEq/L]) and potassium decreased compared with controls (90.7 +/- 7.9 vs 111.5 +/- 6.7 mmol/L [90.7 +/- 7.9 vs 111.5 +/- 6.7 mEq/L]). Glucose production was decreased in septic rats after six hours when compared with controls (4.7 +/- 1.5 vs 15.4 +/- 6.4 mumol/g hepatocytes). These data suggest that hepatic blood flow is decreased before alterations in intracellular sodium and potassium as well as glucose production.

Lack of effect of aldosterone on intracellular sodium and potassium in mononuclear leucocytes from patients with pseudohypoaldosteronism.

In three patients with pseudohypoaldosteronism the effects of aldosterone on intracellular sodium and potassium were studied and compared with normal controls in whom aldosterone prevents the loss of sodium and potassium in vitro. Mononuclear leukocytes were incubated with or without aldosterone (1.4 nM) in RPMI-1640 for 1 h at 37 degrees C. After two washes in isotonic MgCl2 the wet cell pellets were weighted and intracellular sodium and potassium determined by flame photometry, results are expressed as mmol/kg wet cells. In the patients intracellular sodium fell from 18, 23 and 29 mmol/kg to 14, 18 and 11 mmol/kg, respectively, in the absence of aldosterone. With aldosterone added to the incubation medium sodium was not different from values obtained without aldosterone (15, 20 and 13 mmol/kg). Corresponding values for potassium were 89, 48 and 75 mmol/kg before and 68, 32 and 51 mmol/kg after incubation without and 69, 36 and 54 mmol/kg after incubation with aldosterone. Thus, incubation with aldosterone did not show an effect on intracellular sodium and potassium as seen in normals. Baseline values of sodium and potassium before the incubation were within the normal range. From these results it is concluded that in patients with pseudohypoaldosteronism the absent or decreased number of mineralocorticoid receptors in mononuclear leucocytes are accompanied by a lack of response of intracellular sodium and potassium to aldosterone in vitro. However, normal baseline intracellular electrolyte concentrations in these patients may indicate that mineralocorticoids are not involved in the maintenance of normal levels of intracellular sodium and potassium.