Body compostion in vivo. VIII. Some physiological implications with respect to extracellular fluid volume arising from the distribution of thiocyanate in sheep

A comparison of the renal response to extracellular fluid volume expansion (5% body weight) was made between 25 normal and 25 chronically hypophysectomized rats. The extracellular fluid compartments averaged 25 ± 1% of body weight in both groups during control, fasted conditions. Extracellular fluid volume increased to 33 ± 1% in hypophysectomized and 34 ± 2% in normal rats during expansion, based on body weight. In addition, filtration fraction was similar in both normal and hypophysectomized rats during control (0·29 ± 0·03 and 0·26 ± 0·02 respectively) and infusion of Ringer–Locke solution (0·24 ± 0·05 and 0·27 ± 0·05 respectively). Thus our results cannot be explained by differences in the degree of expansion or failure to increase filtration in proportion to plasma flow. During infusion of isotonic Ringer–Locke solution, fractional water and sodium excretion both averaged 5·1% in normal rats and only 1·3% and 0·82% respectively in hypophysectomized rats. The ratio of single nephron to whole kidney filtration rate failed to increase as much in hypophysectomized compared with normal rats. Significant increases of fractional volume excretion occurred in both groups by the end of the accessible portion of the proximal tubule. However, fractional water reabsorption was depressed significantly more in normal (mean = 37%) than in hypophysectomized rats (mean = 19%). Fractional water reabsorption in distal tubules was similar in both groups during expansion. Arterial pressure was lower in hypophysectomized rats under control conditions, but showed similar changes during expansion compared with normal rats. Passage time decreased significantly in all groups after Ringer–Locke infusion, but remained prolonged in hypophysectomized rats in proximal and distal tubules. It is concluded that chronic hypophysectomy results in a less efficient renal excretion of volume and sodium chloride load. This inefficiency appears to be related in part to (1) failure of the proximal tubule to depress water reabsorption to a level equivalent to normal rats, and (2) failure to re-distribute flow to outer cortical glomeruli following extracellular fluid volume expansion in hypophysectomized rats.

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Sodium uptake from the gut of freshwater- and seawater-acclimated ducks and gulls

Canadian Journal of Zoology ◽

10.1139/z88-200 ◽

1988 ◽

Vol 66 (6) ◽

pp. 1365-1370 ◽

Cited By ~ 11

Author(s):

M. R. Hughes ◽

J. R. Roberts

Keyword(s):

Extracellular Fluid ◽

Fluid Volume ◽

Extracellular Fluid Volume ◽

Ion Concentration ◽

Plasma Sodium ◽

Salt Glands ◽

Gut Epithelium ◽

Seawater Acclimation ◽

Na Uptake

The first possible regulator of plasma sodium ([Na]pl) and chloride ([Cl]pl) concentrations is the gut epithelium. Its in vivo role in uptake of ingested salt in birds with salt glands has not been evaluated. In the present study the anterior gut 22Na uptake rate was measured in freshwater-acclimated ducks (Anas platyrhynchos) and gulls (Larus glaucescens) and was then measured in the same birds after acclimation to 2/3 seawater. The 22Na was given orally in 7–10 mL of 171 mM NaCl. In ducks, seawater acclimation increased [Na]pl and [Cl]pl but not Na space; in gulls seawater acclimation increased Na space, but not plasma ion concentration. The rate of gut 22Na uptake was the same in ducks and gulls and was not affected by seawater acclimation in either species. As determined from the 22Na distribution between erythrocytes and plasma 3 h after i.v. 22NaCl injection, duck erythrocytes sequestered more (9.3% ± 0.4%) of the load than did gull erythrocytes (6.9% ± 0.3%) (P < 0.001). Although gulls are better hyperosmotic regulators than ducks, there was no difference between the two species in the entry of sodium into the extracellular fluid volume from the gut. Immediately after oral gut loading with dilute saline, freshwater-acclimated gull [Cl]pl, increased more (2P < 0.001) than could be accounted for by equilibration of the administered Cl within the extracellular fluid volume. After gut loading, the increase in [Cl]pl, of freshwater-acclimated ducks was less rapid and could be accounted for by extracellular distribution of the oral Cl load. In seawater-acclimated gulls, [Cl]pl decreased following gut loading, but was unchanged in seawater-acclimated ducks.

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Role of renal arterial pressure in the regulation of extracellular volume in conscious dogs

Clinical Science ◽

10.1042/cs0820247 ◽

1992 ◽

Vol 82 (3) ◽

pp. 247-254 ◽

Cited By ~ 2

Author(s):

Gabriele Kaczmarczyk ◽

Klaus Schröder ◽

Dirk Lampe ◽

Rainer Mohnhaupt

Keyword(s):

Body Weight ◽

Arterial Pressure ◽

Sodium Excretion ◽

Urine Volume ◽

Extracellular Fluid ◽

Fluid Volume ◽

Extracellular Fluid Volume ◽

Conscious Dogs ◽

Central Venous ◽

Infusion Period

1. This study in conscious dogs examined the quantitative effects of a reduction in the renal arterial pressure on the renal homoeostatic responses to an acute extracellular fluid volume expansion. 2. Seven female beagle dogs were chronically instrumented with two aortic catheters, one central venous catheter and a suprarenal aortic cuff, and were kept under standardized conditions on a constant high dietary sodium intake (14.5 mmol of Na+ day−1 kg−1 body weight). 3. After a 60 min control period, 0.9% (w/v) NaCl was infused at a rate of 1 ml min−1 kg−1 body weight for 60 min (infusion period). Two different protocols were applied during the infusion period: renal arterial pressure was maintained at 102 ± 1 mmHg by means of a servo-feedback control circuit (RAP-sc, 14 experiments) or was left free (RAP-f, 14 experiments). 4. During the infusion period, in the RAP-sc protocol as well as in the RAP-f protocol, the mean arterial pressure increased by 10 mmHg, the heart rate increased by 20 beats/min, the central venous pressure increased by 4 cmH2O and the glomerular filtration rate (control 5.1 ± 0.3 ml min−1 kg−1 body weight, mean ± sem) increased by 1 ml min−1 kg−1. 5. Plasma renin activity [control 0.85 ± 0.15 (RAP-f) and 1.08 ± 0.23 (RAP-sc) pmol of angiotensin I h−1 ml−1] decreased similarly in both protocols. 6. Renal sodium excretion, fractional sodium excretion and urine volume increased more in the RAP-f experiments than in the RAP-sc experiments (P<0.05), renal sodium excretion from 8.2 to 70.1 (RAP-f) and from 7.7 to 47.4 (RAP-sc) μmol min−1 kg−1 body weight, fractional sodium excretion from 1.1 to 8.0 (RAP-f) and from 1.0 to 5.4 (RAP-sc)% and urine volume from 39 to 586 (RAP-f) and from 38 to 471 (RAP-sc) μl min−1 kg−1 body weight. 7. In the RAP-f experiments as well as in the RAP-sc experiments, urinary sodium excretion increased with expansion of the extracellular fluid volume, which increased by a maximum of 21% (fasting extracellular fluid volume: 206 ± 4 ml/kg body weight, six dogs, 28 days). 8. The increase in renal arterial pressure contributed significantly to the renal homoeostatic response, as 21% less urine and 31% less sodium were excreted when the extracellular fluid volume was expanded and the renal arterial pressure was kept constant below control pressure rather than being allowed to rise. The differences in sodium and water excretion were mainly due to the effect of renal arterial pressure on tubular reabsorption. However, the striking increase in sodium and urine excretion which occurred despite the reduction in renal arterial pressure emphasizes the importance of other homoeostatic factors involved in body fluid regulation.

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SERIAL DETERMINATIONS OF EXTRACELLULAR FLUID VOLUME USING THE RADIOSULPHATE SPACE METHOD

Canadian Journal of Biochemistry and Physiology ◽

10.1139/o63-058 ◽

1963 ◽

Vol 41 (2) ◽

pp. 497-510 ◽

Cited By ~ 9

Author(s):

Beverley Murphy ◽

J. B. Dossetor ◽

J. C. Beck

Keyword(s):

Body Weight ◽

Diurnal Variation ◽

Extracellular Fluid ◽

Time Of Day ◽

Fluid Volume ◽

Extracellular Fluid Volume ◽

Blood Levels ◽

Electrolyte Balance ◽

Serum Samples ◽

Space Method

The fate of injected and ingested radiosulphate was investigated. The appearance of radiosulphate in bile was shown to be very rapid. Ingested radiosulphate was rapidly and completely absorbed, peak blood levels occurring at 1 to 2 hours.The sulphate space method of measuring extracellular fluid volume was studied and a method adopted requiring two serum samples taken at 1/2 and 6 hours following injection. This procedure provided a convenient means of making independent observations of extracellular fluid volume as often as four times a day in individual subjects. When values for the sulphate space were compared in the same individuals under conditions similar with respect to diet, activity, and time of day, the coefficient of variation was calculated to be ± 5.7% or about ± 1% of body weight. Values among well-nourished subjects with no known abnormalities of water or electrolyte balance gave a mean of 17.5% body weight with a range of 13.5 to 22% body weight. Values among obese subjects averaged 12.8% body weight.Studies of the diurnal variation of the sulphate space made every 6 hours throughout the day suggested that in man, under conditions of uniform intake and normal activity, there is a diurnal variation of extracellular fluid volume, higher values occurring at night.

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Dehydration in Infancy: Hospital Treatment

Pediatrics in Review ◽

10.1542/pir.11.5.139 ◽

1989 ◽

Vol 11 (5) ◽

pp. 139-143

Author(s):

Harold E. Harrison

Keyword(s):

Body Weight ◽

Intestinal Obstruction ◽

Plasma Volume ◽

Potassium Concentration ◽

Extracellular Fluid ◽

Fluid Volume ◽

Extracellular Fluid Volume ◽

Hospital Treatment ◽

Severe Dehydration ◽

Physiologic Function

Dehydration of a degree severe enough to require intravenous replacement of water and electrolytes indicates (1) depletion of extracellular fluid sodium and water to such an extent that reduction of plasma volume results or (2) distortion of the composition of extracellular fluid with consequent disturbance of physiologic function. Such distortion may be marked hypernatremia, severe depletion of extracellular bicarbonate, or disturbances of potassium concentration resulting in either hyperkalemia or hypokalemia. In addition, hypocalcemia or hypomagnesemia may require specific replacement of these ions. EXTRACELLULAR FLUID DEPLETION WITH HYPOVOLEMIA The most important cause of extracellular fluid depletion in terms of frequency is loss of gastrointestinal secretions through either diarrhea or vomiting. In persons with lower intestinal obstruction, sequestration of gastrointestinal secretions in dilated loops of intestine may be sufficient to cause dehydration in the absence of vomiting. In infants with diarrhea, the onset of vomiting usually is an indication for intravenous replacement of electrolyte and water deficits. Oliguria is also an important item of information, indicating that dehydration is severe enough to require parenteral fluids. It has been estimated that hypovolemia and reduced glomerular filtration with oliguria results when about one third of extracellular fluid volume has been lost. In an infant, the normal extracellular fluid volume is 25% of body weight; therefore, a loss of 8% of body weight as extracellular fluid would result in the manifestation of severe dehydration with reduction of plasma volume.

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SERIAL DETERMINATIONS OF EXTRACELLULAR FLUID VOLUME USING THE RADIOSULPHATE SPACE METHOD

Canadian Journal of Biochemistry and Physiology ◽

10.1139/y63-058 ◽

1963 ◽

Vol 41 (1) ◽

pp. 497-510 ◽

Cited By ~ 1

Author(s):

Beverley Murphy ◽

J. B. Dossetor ◽

J. C. Beck

Keyword(s):

Body Weight ◽

Diurnal Variation ◽

Extracellular Fluid ◽

Time Of Day ◽

Fluid Volume ◽

Extracellular Fluid Volume ◽

Blood Levels ◽

Electrolyte Balance ◽

Serum Samples ◽

Space Method

The fate of injected and ingested radiosulphate was investigated. The appearance of radiosulphate in bile was shown to be very rapid. Ingested radiosulphate was rapidly and completely absorbed, peak blood levels occurring at 1 to 2 hours.The sulphate space method of measuring extracellular fluid volume was studied and a method adopted requiring two serum samples taken at 1/2 and 6 hours following injection. This procedure provided a convenient means of making independent observations of extracellular fluid volume as often as four times a day in individual subjects. When values for the sulphate space were compared in the same individuals under conditions similar with respect to diet, activity, and time of day, the coefficient of variation was calculated to be ± 5.7% or about ± 1% of body weight. Values among well-nourished subjects with no known abnormalities of water or electrolyte balance gave a mean of 17.5% body weight with a range of 13.5 to 22% body weight. Values among obese subjects averaged 12.8% body weight.Studies of the diurnal variation of the sulphate space made every 6 hours throughout the day suggested that in man, under conditions of uniform intake and normal activity, there is a diurnal variation of extracellular fluid volume, higher values occurring at night.

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Comparative Roles of the Renal Apical Sodium Transport Systems in Blood Pressure Control

Journal of the American Society of Nephrology ◽

10.1681/asn.v11suppl_2s135 ◽

2000 ◽

Vol 11 (suppl 2) ◽

pp. S135-S139

Author(s):

PIERRE MENETON

Keyword(s):

Collecting Duct ◽

Extracellular Fluid ◽

Pressure Control ◽

Fluid Volume ◽

Extracellular Fluid Volume ◽

Transport Systems ◽

Salt Diet ◽

Fluid Homeostasis ◽

Low Salt

Abstract.Human genetic studies suggest that the genes encoding renal apical Na+transport proteins play an essential role in the control of extracellular fluid volume and BP. Mice with mutations in each of these genes provide the unique opportunity to directly assess their respective involvement in fluid homeostasis and BP controlin vivo. Inactivation of either the epithelial Na+channel (ENaC) or the Na+-Cl-cotransporter decreases BP to the same extent in mice fed a low-salt diet, despite a more pronounced perturbation of fluid homeostasis in ENaC-deficient mice. In contrast, inactivation of Na+/H+exchanger 3 (NHE3) or the Na+-K+-2Cl-contransporter reduces BP with a normal-salt diet and renders mice unable to survive with a low-salt diet. Therefore, the general conception that ENaC in the collecting duct is the main renal controller of Na+balance and extracellular fluid volume should be tempered. For example, NHE3 in the proximal convoluted tubule seems to play a more substantial role in the control of fluid homeostasis. The overall effect of NHE3 inacthvation on BP may also involve absorptive defects in the intestine and colon, where the exchanger normally reabsorbs significant amounts of Na+and water.

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