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At least 865 records · Page 48Linked to original sources

PubMed1983

Chloride-depletion alkalosis with a normal extracellular fluid volume.

Current concepts hold that volume expansion is essential to the correction of chloride-depletion alkalosis (CDA) with chloride repletion in a permissive role. In this scheme, intranephronal fluid reabsorption would be redistributed with increased delivery to the distal nephron where the provided chloride is readily reabsorbed and the limited capacity for bicarbonate reabsorption would promote bicarbonate excretion and correction of CDA. In a model of CDA produced by peritoneal dialysis against 0.15 M NaHCO3, we have shown complete correction of CDA within 24 h without volume expansion by either oral isotonic sodium or chloride salts with 70 mM chloride and despite an obligatory bicarbonate load and negative sodium and potassium balance. During correction of CDA without volume expansion in rats by intravenous isotonic fluids containing 80 mM chloride, fractional fluid and chloride reabsorptions in the proximal convoluted tubule and in the loop segment of superficial nephrons were not different from controls but chloride reabsorption was enhanced in the collecting duct segment and probably within the distal convolution. Despite no differences in serial hematocrits, blood pressure, and measured plasma volume, kidney and nephron glomerular filtration rate (GFR) were reduced in CDA and returned to normal upon recovery 24 h later.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkalosis↗

PubMed1980

[Dopamine and renal homeostatic control of osmolarity and extracellular fluid volume in initial conditions of hydro-saline depletion and retention. II. Relationship between the renal functional parameters].

In hydro-saline depletion dopamine (DA) infusion (0,1 microgram.kg-1.min-1) elicits different renal effects than it does in hydro-saline retention. It is suggested that in hydro-saline depletion DA activates, besides vasal DA receptors, also vasal and tubular adrenergic receptors. Such adrenergic activation, either direct or presynaptically mediated, can account for both the decrease in the hyperemic response and the increase in the anisosmotic sodium reabsorption.

Adult↗

PubMed1980

[Dopamine and renal homeostatic control of osmolarity and extracellular fluid volume in initial conditions of hydro-saline depletion and retention. I. Renal functional parameters].

Renal effects of dopamine (DA) infusion (0,1 micrograms.kg-1.min-1) in healthy human subject are strongly dependent on the basal condition of the extra-cellular fluid volume. The renal vasodilation and the inhibition of isosmotic sodium reabsorption (as % of sodium filtered load) induced by DA in hydro-saline retention are highly blunted in hydro-saline depletion. Moreover the inhibitory effect on anisosmotic sodium reabsorption (as % of sodium distal load), observed in hydro-saline retention, is reversed in hydro-saline depletion. Thus, DA is likely to behave as a sodium excretion regulator.

Adult↗

PubMed1993

Increased body fat mass and decreased extracellular fluid volume in adults with growth hormone deficiency.

OBJECTIVE: Growth hormone deficiency in adults with hypopituitarism has previously received little attention. Recent data, however, suggest that GH deficiency might be essential for the long-term prognosis of these patients. Earlier studies have documented that GH regulates body composition; in this, body composition in adult patients with hypopituitarism including GH deficiency was studied. DESIGN: A follow-up study of patients with hypopituitarism on routine replacement therapy with L-thyroxine, cortisone acetate and sex steroids. PATIENTS: One hundred and six patients (69 males, mean age 52.5 years and 37 females, mean age 53.4 years) diagnosed as having growth hormone deficiency on the basis of low IGF-I concentration or a maximum GH-response less than 5 mU/l after an insulin/glucagon tolerance test. MEASUREMENTS: Body composition was estimated from body weight, total body water and total body potassium and the results were compared with values predicted from height, weight, age and sex, using data from a large number of healthy subjects. RESULTS: The total body water was significantly lower than that predicted from the observed body weight (P < 0.001), as was the extracellular water (P < 0.001) and the extracellular/intracellular water quotient (P < 0.001). On average, the body cell mass was similar to the predicted value, but the observed/predicted body cell mass ratio correlated positively with age at follow-up. The body cell mass was lower than predicted in subjects below the age of 50 years (P < 0.01). The body fat was higher than predicted (P < 0.001); the increases was also noted in lean subjects. The observed body weight in male subjects was 7.5 kg higher (P < 0.001) than that predicted from healthy subjects of the same body height, a difference explained by an average increase of 6.6 kg in the body fat (P < 0.001) and 1.6 kg in the body cell mass, with a simultaneous reduction of 0.7 kg in the extracellular water (NS). Male patients suffering from untreated androgen deficiency had lower body cell mass than those on androgen treatment. Female subjects weighed 3.6 kg (NS) more on average than healthy women, a difference explained by an increase in the body fat of 6.0 kg (P < 0.001) with a simultaneous decrease of 2.4 kg in the extracellular water (P < 0.001). The body cell mass was similar to that seen in the controls. CONCLUSIONS: Adult patients with growth hormone deficiency have an increased body weight compared to normals of the same age, sex and height, due to an increment of the body fat with a simultaneous reduction in the total body water.

Adolescent↗

PubMed1991

Aldosterone as a factor regulating extracellular fluid volume.

This review focuses on the fact that, for aldosterone to play its role as a regulator of blood volume through its sodium-retaining action, chloride must be retained as well. In fact, amphibian skin reacts to this hormone in terms of chloride conductance as well as active transepithelial sodium transport, both of which increase. The ions move along distinct transepithelial pathways, the principal cells being involved in sodium transport, and mitochondria-rich cells in chloride movement. In this context, it is relevant to emphasize that the collecting duct of mammalian nephron is also heterogeneous in terms of cell types.

Aldosterone↗

PubMed2000

Sibutramine, a serotonin uptake inhibitor, increases dopamine concentrations in rat striatal and hypothalamic extracellular fluid.

We measured, using microdialysis, the effects of sibutramine, given intraperitoneally, on brain dopamine and serotonin flux into striatal and hypothalamic dialysates of freely moving rats, and on the uptake of [(3)H]-DA into striatal synaptosomes. For microdialysis experiments, samples collected every 30 min were assayed by high-pressure liquid chromatography, in a single run. Administration of a low dose of sibutramine (2.0 mg/kg, i.p) had no effect on dopamine or serotonin concentrations in striatal dialysates but higher doses increased both: 5 mg/kg increased these concentrations to 196+/-24% (p<0.01) and 221+/-28% (p<0.01) of baseline, respectively; 10 mg/kg increased dopamine to 260+/-66% (p<0.01) and serotonin to 160+/-20% (p<0.05) of baseline. In hypothalamus, the 5 mg/kg sibutramine dose increased the dopamine concentration to 186+/-40% (p<0.05) and that of serotonin to 312+/-86% (p<0.01) of baseline, while the 10 mg/kg (i.p.) dose increased dopamine to 392+/-115% (p<0.01), and serotonin to 329+/-104% (p<0.01) of baseline. In vitro, sibutramine blocked [(3)H]-dopamine uptake into striatal synaptosomes, with an IC(50) value of 3.8 microM. These findings indicate that sibutramine has at least as great an effect on brain extracellular dopamine levels as on brain serotonin, and suggest that the drug's antiobesity action may result from the changes it produces in brain dopamine as well as serotonin metabolism.

Amphetamine↗

PubMed1996

Hypertension in African Americans: the role of sodium chloride and extracellular fluid volume.

African Americans show higher blood pressure earlier in life, and have a greater incidence of hypertension that is manifest earlier, is more severe and is associated with a greater risk of cardiovascular complications as compared with their white colleagues. Although a variety of mechanisms have been implicated in this phenomenon, a single abnormal factor is unlikely. The role of sodium (salt) sensitivity of blood pressure, renal function, related vasoactive factors, and intracellular ion transport systems will be briefly reviewed for their potential involvement. Speculative hypotheses concerning potential causes of the enhanced salt-sensitivity observed in African Americans will be offered. The implications of these findings for the treatment of hypertension in African Americans will also be briefly discussed.

Antihypertensive Agents↗

PubMed1988

The protein content of extracellular fluids and its relevance to the study of ionic regulation: net charge and colloid osmotic pressure.

1. Protein net charge in blood plasma and haemolymph is relevant to overall anion-cation balance, Donnan equilibria, colloid osmotic pressures (COPs), buffering and liquid junction potentials, but its definition and measurement are not always straightforward. 2. Normal values of protein net charge in man and other animals are discussed, as is their dependence on pH. 3. Although it is clear that charge on a protein augments COP, the theory of COP is still incomplete. 4. The dependence of COP on protein and salt concentrations and on pH are therefore considered empirically. 5. Normal values for COP in various animals are given and the regulation of COP is discussed.

Acid-Base Equilibrium↗

PubMed1979

Dibutyryl cyclic adenosine 3',5'-monophosphate: its role in regulation of cat brain extracellular fluid.

The role of dibutyryl cyclic adenosine 3',5'-monophosphate (db cAMP) in influencing the water content of the cat's gray and white matter was evaluated by intracoritcal injection of 20 micrio L of 2 x 10(-1) to 2 x 10(-6)M solution of db cAMP. Cholera toxin, a stimulator of adenylate cyclase, also was tested. Concentrations of db cAMP less than 10(-3)M failed to produce significant change in brain water content, while concentrations greater than 10(-2)M produced 31.5% +/- 8% and 17.3% +/- 3.6% increases in white matter volume, respectively (P less than .05). Cholera toxin did not increase brain water levels. These results are discussed in relation to the pathophysiology of brain edema.

Animals↗

PubMed1977

Circulating inhibitor of sodium-potassium-activated adenosine triphosphatase after expansion of extracellular fluid volume in rats.

1. Serum was collected from normal rats and from rats volume-expanded with isotonic sodium chloride solution. 2. The serum was fractionated by gel filtration on Sephadex G-25 and each fraction was tested for inhibitory activity against sodium-potassium-activated adenosine triphosphatase prepared from rat kidney homogenate. 3. A single low-molecular-weight fraction, eluting after the salts and after exogenously added lysine-vasopressin, had significantly greater enzyme inhibitory activity when obtained from serum of volume-expanded animals than from control serum. 4. As this fraction has been shown in previous independent studies to contain a natriuretic factor, it may be concluded that one property of this factor is the ability to inhibit sodium-potassium-activated adenosine triphosphatase.

Adenosine Triphosphatases↗

PubMed2000

Concerted actions of renal endothelial and macula densa NO systems in the maintenance of extracellular fluid volume.

It is now clear that nitric oxide (NO) exerts a substantial influence on renal function and that the kidney has a high capacity to produce NO. However, there are at least two different NO systems in the kidney. The interplay between NO generated by the endothelium and by the macula densa is considered in this review. It seems that endothelial NO increases in response to an increase in perfusion pressure and an increase in distal delivery, whereas macula densa NO decreases upon a sustained increase in distal delivery. Furthermore, evidence is accumulating that macula densa NO may well mediate renin release. Though seemingly in contrast, both the response of the endothelial NO and of the macula densa NO system seem appropriate to restore a perturbation of fluid balance. The function of the tubuloglomerular feedback (TGF) mechanism is likely to be influenced by both sources of NO, because of the close proximity of these NO producing cells to the vascular smooth muscle cells of the afferent arteriole. The endothelial NO system seems to be responsible for short-term, dampening actions to increased afferent arteriolar tone elicited by activation of the TGF system. The macula densa NO system, on the other hand, is probably adapting TGF responses to sustained increases in distal delivery. The analysis presented in this paper is an attempt to integrate the function of the two NO systems into physiological regulation. The exact role of the medullary NOS enzymes remains to be further elucidated.

Angiotensin II↗

PubMed1981

Participation of the liver receptors in the regulation of ion composition osmolality and extracellular fluid volume.

Characteristics of 106 fibres dissected from liver afferent nerves were examined on 52 cats anaesthetized with intravenous nembutal administration. The afferent discharge of these fibres has been recorded during intraportal infusions of the different test solutions (75, 300, 450 mM sodium chloride; 8, 10.7 mM potassium chloride in normal saline; 300, 600 mM glucose and mannitol in normal saline and water). The results of the experiments showed that hepatic afferent fibres differ from each other in the following: spontaneous discharge rate, response to different stimuli, threshold, and the adaptation rate. Various receptor units responded specifically to a change either in the intraportal volume, or the osmolality, or both to NaCl and KCl concentration in the portal circulation. These data suggest an existence in the liver of highly specific receptor's populations: mechano(volume)-, osmo-, Na+-sensitive and K+-sensitive one. These receptors can serve as an informative link in the regulation of the water-salt homeostasis.

Animals↗

PubMed1967

Changes in proximal and distal tubular reabsorption produced by rapid expansion of extracellular fluid.

Acute infusions of isotonic saline in the rat cause an increase in glomerular filtration rate and in the excretion of salt and water. The kidney swells, due to expansion of tubular and interstitial volume. Despite the increase in tubular diameter, transit time through the proximal tubules and loops of Henle is decreased, presumably owing to a greatly accelerated rate of tubular flow. Proximal tubular reabsorption, measured in blocked tubules, is inhibited in a way that cannot be ascribed to changes in tubular diameter. The prolongation of proximal reabsorptive half-time is not affected by the administration of aldosterone. It occurs equally in rats chronically loaded with or deprived of salt, and it is therefore not likely that it is influenced by the renal content of renin. In contrast, reabsorption from the distal convoluted tubule is enhanced by saline infusion. This change is observed in segments of tubules blocked with oil and isolated from their glomeruli and thus appears to occur independently of changes in glomerular filtration or tubular flow.

Aldosterone↗

PubMed1982

Glomerular filtration rate and extracellular fluid volume in insulin-dependent patients with diabetes mellitus.

To investigate whether the increased GFR in diabetic patients is related t an increased ECV, GFR ([51Cr] EDTA clearance) and ECV (distribution volume of [51Cr] EDTA) was determined in 26 insulin-dependent diabetic men aged 17 to 50 years (duration of disease 0.1 to 14 years) and compared to the results in normal men. Mean standard GFR +/- SD (that is, GFR corrected to a body surface area of 1.73 m2) was significantly higher in the diabetics than in 26 age-matched controls (127 +/- 21 ml/min vs. 107 +/- 15 ml/min, P less than 0.001). The same held true for the renal function assessed as the ratio GFR/ECV (0.58 +/- 0.10 hr-1 vs. 0.51 +/- 0.07, P less than 0.05). Regression analysis showed that the relation between ECV and body weight and between ECV and body surface area was the same in the diabetic patients as in 44 controls. The increased GFR but normal ECV indicates that the GFR alteration in diabetic patients reflects a real hyperfunction.

Adolescent↗

PubMed1984

Oscillations of medullary extracellular fluid pH caused by breathing.

The purpose of this study was to determine if respiratory oscillations of arterial PCO2 are transmitted to the medullary ECF. Anesthetized, paralyzed cats whose vagi and carotid sinus nerves had been cut were studied. A flat surfaced pH electrode (2 mm in diameter) and a specially built differential amplifier were used to measure pH on the ventral surface of the medulla. Elimination of noise and high sensitivity were obtained by integrating the output from the pH amplifier with a digital voltmeter . We measured ECF pH oscillations that had the same period as the ventilator. The amplitude of the oscillations was about 0.006 unit when the ventilator was slow (less than 10/min). The amplitude decreased progressively as the rate was increased and oscillations were usually undetectable at rates above 25/min. Experiments were performed that ruled out mechanical artifact and ventilator-related fluctuations in arterial pressure as being causal. We conclude that oscillations of alveolar CO2 are transmitted to the brain by the circulation and result in oscillations of ECF pH.

Animals↗

PubMed1976

The blood: bone disequilibrium. II. Evidence against the active accumulation of calcium or phosphate into the bone extracellular fluid.

An attempt was made to quantitate in vitro the unidirectional fluxes of Ca2+ and Pi across periosteal and endosteal membranes of frontal bones from calvaria of 20 day chick embryos. The influx of Ca2+, as previously reported, seemed to be passive [12]. The uncoupler, CCCP, had no effect on the influx of Ca2+, but increased both the endosteal and periosteal effluxes. La2+ decreased the influx of Ca2+. The influx of phosphate was also passive and proportional to the concentration of phosphate. The influx was unaffected by either iodoacetate or CCCP, but increased when the periosteal and endosteal membranes were removed; the efflux of phosphate was greater from the endosteal side and was unaffected by CCCP, while iodoacetate increased both the periosteal and endosteal effluxes. The evidence presented refutes the generally accepted hypothesis that Ca2+ (or phosphate) fluxes into and out of bone are governed by a pumpleak system. However, the increase in rate of influx when the cellular layers are removed indicates that the periosteum and endosteum constitute an important structural conponent in the maintenance of bone mineral and its equilibration with the circulation.

Animals↗

PubMed1992

Regulation of sodium metabolism and extracellular fluid volume during development.

In addition to regulating developmental changes in body fluid content, the newborn kidney must maintain a positive sodium balance to ensure adequate body growth. Mechanisms by which the developing organism perceives changes in volume and the manner in which the kidney responds to these changes have been reviewed. Perception of changes in ECF volume is sensed by volume receptors that involve central nervous system signal processing (e.g., low- and high-pressure volume receptors) before influencing the kidney by way of the renal nerves or that are directly coupled with the kidney and do not involve central nervous system processing (e.g., juxtaglomerular apparatus, ANF, hepatic factors). Results presently available demonstrate that these mechanisms are functional early in life and that their sensitivity changes during development in accordance with the needs of the organism. In addition, the developing kidney has unique characteristics that allow it to maintain a positive sodium balance necessary for growth.

Adult↗

PubMed1988

Effect of osmolar and ionic composition of the extracellular fluid on transferrin endocytosis and exocytosis and iron uptake by reticulocytes.

The effects of osmolar and ionic factors on endocytosis and exocytosis were investigated using rabbit reticulocytes and 125I-59Fe labelled transferrin. Endocytosis and exocytosis of transferrin and the uptake of iron were inhibited by increasing the osmolality or decreasing the ionic strength or pH of the cell incubation medium. However, elevation of the pH above 8.0 inhibited endocytosis but not exocytosis. Replacement of the NaCl in the incubation medium by Nal, NaF, NaSCN, NaClO4, Na2SO4, Na phosphate, or Na Hepes inhibited endocytosis and iron uptake but only Nal, NaF, and NaSCN inhibited exocytosis. Transferrin exocytosis was insensitive to inhibitors of anion or cation transport, but endocytosis and iron uptake were inhibited by several anion transport inhibitors. Overall, transferrin endocytosis was more sensitive than exocytosis to most of the factors which were investigated, and the effects on the rates of endocytosis and iron uptake were quantitatively very similar. The results provide strong support for the concept that transferrin endocytosis is a necessary step in iron uptake by reticulocytes. They do not support the chemiosmotic models of exocytosis in their present formulations, but do not rule out the possible role of an osmotic event in exocytosis.

Ammonium Chloride↗