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PubMed2004

Discovery and neurochemical screening of peptides in brain extracellular fluid by chemical analysis of in vivo microdialysis samples.

Endogenous peptides from brain extracellular fluid of live rats were analyzed using capillary liquid chromatography (LC)-tandem mass spectrometry (MS2). A 4-mm-long microdialysis probe perfused at 0.6 microL/min implanted into the striatum of anesthetized male rats was used to collect 3.6 microL dialysate fractions that were injected on-line into the capillary LC-MS2 system for analysis. A total of 3349 MS2 spectra were collected from 13 different animals under basal conditions and during localized depolarization evoked by infusion of a high-K+ solution through the microdialysis probe. Subtractive analysis revealed a total of 859 MS2 spectra that were observed only during depolarization. From these spectra, 29 peptide sequences (25 were peptides not previously observed) from 6 different protein precursors were identified using database searching software. Proteins identified include precursors to neuropeptides, synaptic proteins, blood proteins, and transporters. The identified peptides represent candidates for neurotransmitters, neuromodulators, and markers of synaptic activity or brain tissue damage. A screen for neuroactivity of novel proenkephalin fragments that were found was performed by infusing the peptides into the brain while monitoring amino acid neurotransmitters by microdialysis sampling combined with capillary electrophoresis. Three of the six tested peptides evoked significant increases in various neuroactive amino acids. These results demonstrate that this combination of methods can identify novel neurotransmitter candidates and screen for potential neuroactivity.

Amino Acid Sequence↗
PubMed1976

The blood: bone disequilibrium. I. The active accumulation of K+ into the bone extracellular fluid.

The role of periosteal and endosteal cellular envelopes in the control of the K+ and Na+ content of embryonic chick calvaria was investigated. Data have been presented which suggest that the K+ in extracellular fluid of calvaria may be under a direct membrane control similar to the pump-leak systems hypothesized for most cells. Based on DNA and K+ analysis of cell water, volume and DNA content, the K+ in the bone extracellular fluid was calculated to account for 75% of the total K+ content of intact calvaria. The bulk of K+ is therefore extracellular and its accumulation there was found to be sensitive to the presence of ouabain, iodoacetate, CCCP, and to temperature. Losses of 70% of calvaria K+ were found one hour after addition of 250 muM ouabain. If the exposure to ouabain was brief, the K+ loss was partially reversed. The rate of 42K+ uptake was found to be depressed by ouabain, decreased pH, and La2+. The total Na+ content of these calvaria was found not to vary when incubated with ouabain, iodoacetate, or CCCP.

Animals↗
PubMed1984

Distribution of extracellular fluid over the intra- and extravascular space in hypertensive patients.

The time course of hemodynamic responses to long-standing sodium overload was studied in humans. The study involved six patients who became hypertensive on exposure to excessive mineralocorticoid activity. Arterial pressure, cardiac output, and body fluid volumes were measured with noninvasive methods at weekly intervals for at least 6 weeks and at longer intervals for periods up to 2 years. Extracellular fluid volume was expanded by approximately 20%, and arterial blood pressure rose by 20-40%. Initially, cardiac output was the dominant factor for the pressure rise. But in a later stage the pressure remained high or rose even further, although cardiac output and body fluid volumes fell toward normal. In some cases, particularly in young subjects, it took weeks or months before the total peripheral resistance began to rise, and there was no quantitative relationship between the initial rise in cardiac output and the subsequent rise in resistance. These findings argue against a direct cause-and-effect relation between flow and resistance changes. Preferential expansion of the intravascular compartment was associated with high cardiac output, whereas preferential expansion of the interstitial fluid compartment was associated with high resistance. Thus, the hemodynamic pattern of sodium-induced hypertension seems somehow related to the distribution of extracellular fluid over the intra- and extravascular compartments.

Adenoma↗
PubMed1991

Simultaneous measurement of plasma and brain extracellular fluid concentrations of catechols after yohimbine administration in rats.

The present study examined whether systemic injection of the alpha 2 adrenoceptor blocker, yohimbine, affects concentrations of norepinephrine (NE) and its metabolites in extracellular fluid in the brain and in blood. Microdialysis probes were inserted into the posterior hypothalamus, medulla, and caudate/putamen in rats. Microdialysate and arterial blood were sampled after intravenous administration of yohimbine. In the hypothalamus yohimbine produced significant increases in extracellular fluid concentrations of NE, its intraneuronal metabolite, dihydroxyphenylglycol (DHPG), and methoxyhydroxyphenylglycol (MHPG), a major neuronal and extraneuronal metabolite of NE. The increases in these levels were small or absent in the caudate/putamen, where dopamine is the primary catecholamine transmitter. During systemic infusion of tracer amounts of [3H]NE, little if any radioactive NE or DHPG appeared in the microdialysate, whereas substantial levels of [3H]MHPG were present and increased as plasma [3H]MHPG levels rose. The results support the view that alpha 2 adrenoceptor blockade in the brain increases hypothalamic and medullary release, reuptake, and metabolism of NE. The findings cannot be explained by disruption of the blood-brain barrier for catecholamines by insertion of the microdialysis probes. Enhanced sympathetic outflow and peripheral release of NE when alpha 2 adrenoceptors are blocked appears to be attended by enhanced central NE release, presumably as a result of presynaptic alpha 2 adrenoceptor blockade at noradrenergic terminals in the brain. This is consistent with the hypothesis that central noradrenergic NE release is regulated by presynaptic alpha 2 adrenoceptors.

Animals↗
PubMed1981

Posthemorrhagic changes in plasma water and extracellular fluid volumes in the rat.

Anesthetized rats were submitted to a standardized hemorrhage to 40 mm Hg by withdrawing 35 to 40% of the total blood volume. The plasma water and the extracellular fluid volumes of the whole animal and selected tissues were estimated with 125 I human serum albumin and 51Cr EDTA, respectively, after recovery periods of 10 and 90 minutes. The plasma water volume of the whole animal decreased, but approximately 50% of the shed plasma water was restored within 10 minutes after the hemorrhage. The extracellular fluid volume of the whole animal did not change significantly after hemorrhage, whereas this fluid compartment was regionally reduced in the liver, spleen, and subcutaneous fat after a 10-min recovery period but only in the liver after a 90-min recovery period.

Animals↗
PubMed1989

Effect of extracellular fluid volume contraction and expansion on plasma atrial natriuretic peptide (ANP) concentration in patients with acromegaly.

Atrial natriuretic peptide (ANP) is a hormone release into the circulation by atrial cardiocytes (Gutkowska et al. 1984). Extracellular fluid volume expansion acts as a powerful stimulus for ANP secretion and results in the augmentation of its plasma concentration (Lang et al. 1985). Patients with active acromegaly demonstrate the increased extracellular fluid volume (Falkheden et al. 1964), while a successful treatment of the disease results in the disappearance of hypervolemia (Strauch et al. 1977). We have recently demonstrated that in patients with active acromegaly the increased total body plasma volumes are accompanied by the elevated plasma ANP concentrations, whereas, in the successfully treated patients, both: total plasma volumes and plasma ANP levels do not differ significantly from these in healthy subjects (Czekalski et al. 1988b).

Acromegaly↗
PubMed2004

The influence of extracellular fluid volume on serum proteins in peritoneal dialysis patients.

AIM: Patients on peritoneal dialysis (PD) often present a deficit of serum protein and especially of albumin, due to its loss through the peritoneum and some others factors. Serum albumin is a marker of survival, of nutritional status and is changed in inflammation in renal failure. Correction of the albumin level is difficult and needs a dietary or other supplementation. Some suspicions exist that a reduction exist that a reduction in overhydration in PD patients may improve serum proteins, particularly albumins. The study tries to prove or to deny the thesis, investigating 27 PD patients (cycler PD, CPD) during 6 weeks. METHODS: Body weight, blood pressure, total serum protein, albumin, C-reactive protein, 24-h urine and volume of the dialysate solution were measured at the first and the final week. The extracellular fluid volume was evaluated by multiple-frequency bioelectrical impedance. Dialysis prescription was changed between the 0- and 6-week to increase the daily ultrafiltrate volume (1.00+/-0.87 1 to 1.32+/-0.85 1, p<0.05). RESULTS: There was a significant reduction in body weight (p<0.001), extracellular fluid volume (p<0.001), systolic blood pressure (p<0.001), diastolic blood pressure (p<0.01). Serum albumin increased significantly (p<0.01), there was a trend to augmentation of total protein and C-reactive protein did not change. CONCLUSIONS: The study suggests that overhydration has only a light influence on total serum protein, but impacts significantly the serum albumin level and blood pressure as well. The reduction in body weight can be a helpful way to overcome the hypoalbuminemia and hypertension i.e. to improve the survival time of patients on continuous ambulatory peritoneal dialysis.

Blood Proteins↗
PubMed2002

Pilot study on lipocalin expression into extracellular fluids of women in fertile age.

BACKGROUND: To verify the expression of neutrophil gelatinase associated lipocalin (NGAL), molecule now arising great interest because of its proposed involvement in cell-cycle regulation, acute phase response and immunomodulation, into extracellular fluids of female reproductive tract, in order to provide useful data to understand its biological functions. The data collected are purely qualitative, just meant to reveal the presence of lipocalin into the assayed fluids, and they have to be considered as preliminary for a quantitative study (in progress at the moment) based on a double antibody radioimmunoassay. METHODS: Three kinds of extracellular fluid were randomly sampled: amniotic fluid (13 samples), cervical mucus (10 samples), coloster (20 samples). The inclusion criteria concerning the selection of the donor women were: age (fertile period), healthy state and pregnancy state. All the samples underwent protein assay, electrophoresis and western blot. RESULTS: All the samples examined revealed NGAL's presence. CONCLUSIONS: The positive results of this study seem to strengthen the hypothesis related to NGAL biological functions, specifically the ones that suggest its role into cell differentiation, embryonic development and inflammation. Therefore the female reproductive tract is suggested as a new promising study object in this research field.

Acute-Phase Proteins↗
PubMed1996

Contrast media as extracellular fluid space markers: adaptation of the central volume theorem.

We present some theoretical observations on the pharmacokinetics of the conventional intravascular radiographic and gadolinium chelate MR contrast agents. These agents may be viewed from a physiological perspective as extracellular fluid (ECF) space markers. It can be shown that the passage of such agents through the body may be described by a variant of the "central volume theorem", if the central volume is taken to be that of the entire extracellular fluid. A consequence is that, in a manner akin to nuclear medicine techniques utilizing technetium-99m diethylene triamine pentacetic acid (DTPA), measures of glomerular filtration rate (GFR) related to total ECF volume rather than to the normal body surface area may be obtained from direct or indirect measurements of iodine or gadolinium plasma levels. Typical measurements are presented. A simple means is also described of generating curves of the fraction of contrast medium excreted from the body, applicable to both patients with normal and with abnormal renal function.

Biomarkers↗
PubMedDate not supplied

[Changes in plasma and extracellular fluid volumes and plasma protein mass under conditions of head-down tilt hypokinesia and immersion].

Twenty-four young volunteers were exposed to 30-56-hour head-down tilting (at -6 degrees and -15 degrees) in 5 experimental runs. The purpose of the study was to measure volumes of plasma and extracellular fluid, as well as concentrations of plasma proteins and hemoglobin. The results varied but in most cases the plasma volume decreased by 0.46-0.55 1, extracellular fluid volume by 0.75-2.15 1, and plasma proteins by 13.4-30.4 g. The hemoglobin concentration increased by 8-12% and that of plasma proteins in some cases grew and in others diminished. Water loading prevented the plasma volume decrease. The paper discusses with reference to the data in the literature the fate and role of plasma proteins in the regulation of the intravascular volume and fluid redistribution.

Adult↗
PubMed1986

Saralasin blocks the effect of angiotensin II and extracellular fluid saline expansion on the Na-K-ATPase inhibitor release in rats.

A low molecular weight substance which behaves like ouabain as inhibitor of brain membrane Na-K-ATPase and 3H-ouabain binding was found in plasma after saline expansion of extracellular fluid or angiotensin II infusion into the third brain ventricle in the rat. Intracerebroventricular infusion of angiotensin II antagonist, saralasin, blocks the increase of the Na-K-ATPase inhibitor produced by infusion of angiotensin II into the third ventricle or extracellular fluid saline expansion.

Angiotensin II↗
PubMed1992

Alpha 1-adrenoceptor-mediated Ca(2+)-entry from the extracellular fluid and Ca(2+)-release from intracellular stores: no role for alpha 1A,B-adrenoceptor subtypes in the pithed rat.

1. In the present study, we tested the hypothesis that in the pithed rat preparation two subtypes of the alpha 1-adrenoceptor are linked to two different signal transduction mechanisms, both of which contribute to vasoconstriction, one facilitating Ca(2+)-entry from the extracellular fluid (alpha 1A) and one promoting the release of Ca2+ from intracellular sources (alpha 1B). 2. The selective alpha 1A-adrenoceptor antagonist, 5-methyl-urapidil, and the selective alpha 1B-adrenoceptor antagonist, chloroethylclonidine, were unable to discriminate between alpha 1-adrenoceptor-mediated pressor responses, which relied on an entry of extracellular Ca2+ sensitive to nifedipine and an intracellular release of Ca2+ insensitive to nifedipine, respectively. 3. Chloroethylclonidine, 12.5 and 25 mg kg-1 i.v., were equieffective, and had only minor effects on alpha 1-adrenoceptor-mediated increases in diastolic blood pressure. This could be associated with a small decrease in the receptor-reserve of the pithed rat preparation due to irreversible receptor blockade by this antagonist. These data indicate that chloroethylclonidine-sensitive alpha 1-adrenoceptors constitute only a minor fraction of the total alpha 1-adrenoceptor population on rat arterial resistance vessels. 4. Chloroethylclonidine behaved as a partial agonist eliciting a small increase in baseline diastolic blood pressure which could be inhibited by Ca(2+)-entry blockade with nifedipine. 5. Chloroethylclonidine potentiated the pressor responses elicited by the alpha 2-adrenoceptor agonists UK-14,304 and azepexole (B-HT 933). 6. No evidence was found in the pithed rat that alpha 1-adrenoceptor-mediated Ca(2+)-entry from the extracellular fluid and Ca(2+)-release from intracellular stores are mediated by alpha 1A and alpha 1B-adrenoceptors, respectively.

Adrenergic alpha-Antagonists↗
PubMed1982

Fast bicarbonate-chloride exchange between plasma and brain extracellular fluid at maintained PCO2.

The aim of this paper was to investigate the kinetics and mechanism of bicarbonate exchange at the blood-brain ECF barrier. The experiments were performed on anaesthetized and artificially ventilated cats in such a way that acid-base parameters of the brain extracellular fluid were continuously measured while an approximately rectangular increase in the arterial plasma bicarbonate concentration was produced at maintained PCO2. The results from such a preparation were: 1. A rapid increase in the brain extracellular bicarbonate concentration was observed in response to an i.v. bolus injection of 3 ml molar NaHCO3. The bolus was followed by a slow infusion of bicarbonate solution. The brain extracellular bicarbonate reached a new steady state within a minute. 2. This increase was almost simultaneously accompanied by a decrease in the extracellular chloride concentration. The HCO-3-Cl- exchange ratio very closely approached one. 3. The extracellular bicarbonate concentration in the brain, after an initial increase, returned towards control in spite of elevated arterial bicarbonate at maintained PCO2. 4. The results are discussed in terms of a 5-compartment model, where the extracellular fluid is interposed between the glial cells and the interstitial side of the endothelial cells, similar to the blood plasma being interposed between the red cells and the luminal side of the endothelial cells. 5. A non-electrogenic carrier-mediated HCO-3-Cl- exchange at the interphase of the blood brain barrier is postulated.

Animals↗
PubMed1977

The pH of brain extracellular fluid in the cat.

1. The blood supply to the medulla was determined by the injection of indian ink via the vertebral arteries. Virtually the whole medulla was supplied by penetrating vessels from the ventral surface. The highest density of small arterioles and venules was found close to the roots of XII and on the ventrolateral surface.2. The pH of extracellular fluid (pH(e.c.f.)) was measured with pH microelectrodes of tip size 1-3 mum in cortex and medulla in seventeen cats, anaesthetized with pentobarbitone or a chloralose-urethane mixture. Parallel measurements were made of the pH of c.s.f. and plasma, the DC potential between plasma and brain and ventilation or phrenic nerve discharge.3. In the majority of tests under steady conditions, the pH of e.c.f. was found to be lower than that of c.s.f. by between 0.03 and 0.08 units. No systematic pH gradients could be found to a depth of 5 mm beneath the surface of either medulla or cortex.4. When plasma P(CO2) was altered, pH(e.c.f.) changed with a latent period and speed of response related to the density of blood vessels. In vascular areas of the medulla and in the cortex, the latent period of 4 sec and the change of pH(e.c.f.) coincided with changes in ventilation. Changes in pH(c.s.f.) over the same areas were invariably slower.5. CO(2) buffering capacities were in the order plasma > e.c.f. > c.s.f. Typical values were respectively, -2.2, -2.1 and -1.6.6. The pH of e.c.f. was unaffected by the intravenous injection of H+ and only slowly by the injection of HCO(3)-. Only up to a depth of 1 mm beneath the surface was pH(e.c.f.) affected by superfusion of mock c.s.f. in the range 6.8-8.0 units. This response had a latent period of 2-3 min and was complete in 15 min.7. The pH of e.c.f. fell with hypoxia after a latent period of > 1 min and if all vasosensory nerves had been cut, pH(e.c.f.) was markedly affected by changes of blood pressure.8. These results indicate that even under steady conditions, the pH of e.c.f. and c.s.f. is not identical, that pH(e.c.f.) is more obviously affected by changes in P(a, CO2) than pH(c.s.f.) and that putative H+ sensors which drive respiratory neurones are likely to be similarly affected.

Animals↗
PubMed1976

Oral administration of radioactive sulfate to measure extracellular fluid space in man.

Radioactive sulfate-35 (35S) was administered to eight human subjects intravenously and orally, to compare respective kinetics of distribution. Intravenously administered 35S attained equilibration within 60-90 min. Orally administered 35S attained equilibration within 60-105 min and thereafter achieved plasma activity equivalent to the intravenously administered tracer. Eighty percent or greater of the 35S dose was recovered in the 24-h urine, following either intravenous or oral administration. The mean extracellular fluid space demonstrated less than 9% mean difference between routes of administration. It is concluded that 35S is completely absorbed at tracer doses, and may be administered orally as a reliable substitute for intravenously administered 35S for measuring extracellular fluid space.

Administration, Oral↗
PubMed1987

Extracellular fluid and plasma volumes during water immersion in nephrectomized dogs.

Extracellular fluid volume (ECF, [125I]iothalamate space), blood volume (BV, 51Cr-labeled erythrocyte space), and hematocrit were measured continuously to study the kinetics of fluid movements between intracellular, interstitial, and plasma compartments during water immersion (WI) at 38 degrees C in seven splenectomized and acutely nephrectomized dogs. ECF and plasma volume (PV) increased linearly during WI by 10 +/- 2 ml/kg (4% of initial ECF volume, P less than 0.05) and 12 +/- 2 ml/kg (33% of initial PV, P less than 0.05), respectively, above the control level by 120 min of WI. We estimate that 83% of the fluid entering the intravascular compartment is derived from the intracellular space at 120 min of WI. The results of this study indicate that WI leads to a sustained fluid movement of intracellular fluid toward the intravascular compartment. The increase in interstitial hydrostatic pressure (wick method) by 28.5 mmHg from the control level at 5 min of WI in response to the external water pressure exceeds the increase in mean capillary pressure by 10-11 mmHg relative to the control level. We postulate that this negative hydrostatic pressure gradient across the capillary wall leads to an increase in PV during WI.

Animals↗
PubMed1980

A simple single injection method for determination of the extracellular fluid volume.

From measurements in eighty-six adults it is shown how the distribution volume of [51Cr]EDTA, as an estimate of the extracellar fluid volume (ECV), can be determined accurately using a simplified single injection method. The method only needs drawing of a few blood samples 3-5 h after a quantitative i.v. injection of [51Cr]EDTA and measurement of the subject's body weight. The glomerular filtration rate (GFR) can be calculated from the same few data, and with it, the ratio ECV/GFR or the reverse ratio GFR/ECV. These easily determined ratios might be relevant measurements of the kidney's main function: regulation of composition and size of the extracellular fluids, since they indicate how often 'that which is to be regulated' (i.e. the extracellular fluids) comes into contact with 'the regulator' (i.e. the kidney).

Adolescent↗