scholarly journals Flow dependence of fluid transport in the isolated superficial pars recta: Evidence that osmotic disequilibrium between external solutions drives isotonic fluid absorption

1981 ◽  
Vol 20 (5) ◽  
pp. 588-597 ◽  
Author(s):  
James A. Schafer ◽  
Susan L. Troutman ◽  
Mary L. Watkins ◽  
Thomas E. Andreoli
Keyword(s):  
Fluid Transport ◽  
Fluid Absorption ◽  
Isotonic Fluid ◽  
Flow Dependence ◽  
Pars Recta

Volume absorption in the pars recta. III. Luminal hypotonicity as a driving force for isotonic volume absorption

1978 ◽  
Vol 234 (4) ◽  
pp. F349-F355 ◽  
Author(s):  
T. E. Andreoli ◽  
J. A. Schafer
Keyword(s):  
Driving Force ◽  
Theoretical Calculations ◽  
Rabbit Kidney ◽  
Fluid Absorption ◽  
Perfusion Rate ◽  
Volume Absorption ◽  
Isotonic Fluid ◽  
Nacl Concentration ◽  
Straight Tubules ◽  
Pars Recta

This paper examines the possibility that osmotic disequilibrium between luminal and bathing solutions may account for isotonic fluid absorption coupled to active Na+ absorption observed when superficial proximal straight tubules isolated from rabbit kidney are perfused and bathed with NaCl solutions in the absence of CO2, HCO3-, and luminal organic solutes. If luminal hypotonicity provides a driving force for isotonic fluid absorption under these conditions, the luminal fluid must be nearly isotonic; and steady-state luminal hypotonicity should develop sufficiently rapidly that the absolute rate of volume absorption ('JV, nl min-1) coupled to active Na+ transport is relatively independent of perfusion rate, so that the normalized rate of fluid absorption (JV, nl min-1 mm-1) is approximately constant. Our theoretical calculations indicate that these expectations are fulfilled. A 0.42-0.56 mM reduction in luminal NaCl concentration adequately accounts for the JV observed under such conditions, because of the high hydraulic conductivity of these tubules; and within the range of tubule lengths normally employed with isolated proximal straight tubules, JV is relatively indepedent of perfusion rate within the generally observed range of experimental error.

Effective luminal hypotonicity: the driving force for isotonic proximal tubular fluid absorption

1979 ◽  
Vol 236 (2) ◽  
pp. F89-F96 ◽  
Author(s):  
T. E. Andreoli ◽  
J. A. Schafer
Keyword(s):  
Driving Force ◽  
Fluid Transport ◽  
Driving Forces ◽  
Proximal Tubules ◽  
Diffusion Resistance ◽  
Fluid Absorption ◽  
Isotonic Fluid ◽  
Lateral Intercellular Spaces ◽  
Proximal Tubular ◽  
Editorial Review

This Editorial Review summarizes certain considerations relevant to the mechanism(s) of isotonic fluid absorption by the mammalian proximal nephron. Recent evidence indicates that the paracellular pathway in this epithelium has a low diffusion resistance. Therefore it is possible that lateral intercellular spaces are in diffusion equilibrium with the peritubular medium. For such a circumstance, the driving forces for isotonic fluid absorption may reside in external solutions. But since the hydraulic conductance of mammalian proximal tubules is remarkably high, the effective osmotic pressure gradient between luminal and pertibular solutions required to drive isotonic fluid transport is relatively small. In the mammalian proximal nephron, effective luminal hypotonicity may provide the driving force for isotonic fluid transport. At least two mechanisms could account for the development of effective luminal hypotonicity. First, preferential absorption of bicarbonate results in a rise of luminal Cl- concentration. And because proximal tubules are more permeable to Cl- than to HCO3-, there develops a driving force for isotonic fluid transport. Second, trivial degrees of luminal hypotonicity may develop attendant on active Na+ absorption. We provide evidence that, of these two mechanisms, axial anion asymmetry is the dominant force for isotonic fluid transport.

Dependence of ion fluxes on fluid transport by rat proximal tubule

1986 ◽  
Vol 250 (4) ◽  
pp. F680-F689 ◽  
Author(s):  
K. Bomsztyk ◽  
F. S. Wright
Keyword(s):  
Proximal Tubule ◽  
Fluid Transport ◽  
Rat Kidney ◽  
Water Flux ◽  
Fluid Secretion ◽  
Proximal Convoluted Tubule ◽  
Ion Fluxes ◽  
Fluid Absorption ◽  
Fluid Flux ◽  
K Transport

The effects of changes in transepithelial water flux (Jv) on sodium, chloride, calcium, and potassium transport by the proximal convoluted tubule were examined by applying a microperfusion technique to surface segments in kidneys of anesthetized rats. Perfusion solutions were prepared with ion concentrations similar to those in fluid normally present in the later parts of the proximal tubule. Osmolality of the perfusate was adjusted with mannitol. With no mannitol in the perfusates, net fluid absorption was observed. Addition of increasing amounts of mannitol first reduced Jv to zero and then reversed net fluid flux. At the maximal rates of fluid absorption, net absorption of Na, Cl, Ca, and K was observed. When Jv was reduced to zero, Na, Cl, and Ca absorption were reduced and K entered the lumen. Na, Cl, and Ca secretion occurred in association with the highest rates of net fluid secretion. The lumen-positive transepithelial potential progressively increased as the net fluid flux was reduced to zero and then reversed. The results demonstrate that changes in net water flux can affect Na, Cl, Ca, and K transport by the proximal convoluted tubule of the rat kidney. These changes in net ion fluxes are not entirely accounted for by changes in bulk-phase transepithelial electrochemical gradients.

Isotonic Fluid Absorption during Hysteroscopy Resulting in Severe Hyperchloremic Acidosis

2005 ◽  
Vol 103 (1) ◽  
pp. 203-204 ◽  
Author(s):  
Monika Schäfer ◽  
Britta S. Von Ungern-Sternberg ◽  
Edward Wight ◽  
Markus C. Schneider
Keyword(s):  
Fluid Absorption ◽  
Hyperchloremic Acidosis ◽  
Isotonic Fluid

THE EFFECTS OF MANDUCA SEXTA DIURETIC HORMONE ON FLUID TRANSPORT BY THE MALPIGHIAN TUBULES AND CRYPTONEPHRIC COMPLEX OF MANDUCA SEXTA

1993 ◽  
Vol 178 (1) ◽  
pp. 231-243 ◽  
Author(s):  
N. Audsley ◽  
G. M. Coast ◽  
D. A. Schooley
Keyword(s):  
Cyclic Amp ◽  
Manduca Sexta ◽  
Fluid Transport ◽  
Basal Membrane ◽  
Fluid Secretion ◽  
Hormonal Control ◽  
Malpighian Tubules ◽  
Proximal Tubules ◽  
Fluid Absorption ◽  
Diuretic Hormone

1. Manduca sexta diuretic hormone (Mas-DH) stimulates fluid secretion by adult Malpighian tubules of M. sexta, demonstrating its site of diuretic action in M. sexta for the first time. It was not possible to develop a suitable bioassay to measure fluid secretion in larval proximal tubules. 2. Mas-DH has an antidiuretic action on the cryptonephric complex of larval M. sexta because it increases fluid absorption from the rectum. It appears that in this complex Mas-DH is acting on a Na+/K+/2Cl- co-transporter, presumably on the basal membrane of the cryptonephric Malpighian tubules, because Mas-DH-stimulated fluid absorption by the cryptonephric complex is inhibited by bumetanide or the removal of Cl-, Na+ or K+ from the haemolymph side of the tissue. This is the first demonstration of hormonal control of fluid absorption by the cryptonephric complex. 3. Concomitant with the stimulation of fluid transport, Mas-DH increases the amount of cyclic AMP secreted by adult Malpighian tubules and the cryptonephric complex. In addition, Mas-DH promotes cyclic AMP production by the larval proximal tubules.

Relationship between interdigestive duodenal motility and fluid transport in humans

1990 ◽  
Vol 259 (3) ◽  
pp. G348-G354 ◽  
Author(s):  
H. Sjovall ◽  
I. Hagman ◽  
H. Abrahamsson
Keyword(s):  
Motor Activity ◽  
Phase Ii ◽  
Absorption Rate ◽  
Fluid Transport ◽  
Late Phase ◽  
Fluid Absorption ◽  
Amylase Release ◽  
Duodenal Fluid ◽  
Interdigestive Motility ◽  
Motility Cycle

In 22 healthy volunteers distal duodenal fluid absorption was related to the interdigestive motility cycle. Fluid absorption was measured with a triple-lumen perfusion technique, and motility was registered with a low-compliance pneumohydraulic system. Pancreatic and biliary secretions were estimated by measurement of bilirubin and amylase release into the duodenal segment. Duodenal fluid absorption rate changed during the interdigestive motility cycle; the highest absorption rate was registered during phase I (low-motor activity) and absorption rate then decreased in parallel with increasing motor activity during phase II (r = -0.69, P less than 0.001). In late phase II a net fluid secretion was frequently registered, together with an increased release of bilirubin into the duodenal lumen. This pattern was seen during perfusion with both glucose-containing (30 mM) and glucose-free solutions. The results show that duodenal fluid absorption rate changes markedly during the interdigestive motility cycle. This effect may be a hydrodnamic phenomenon or may be due to activation of a neural secretory mechanism during phase II.

Response to parathyroid hormone in defined segments of proximal tubule

1976 ◽  
Vol 230 (2) ◽  
pp. 286-290 ◽  
Author(s):  
RJ Hamburger ◽  
NL Lawson ◽  
JH Schwartz
Keyword(s):  
Parathyroid Hormone ◽  
Proximal Tubule ◽  
Proximal Convoluted Tubule ◽  
Base Line ◽  
Fluid Absorption ◽  
Functional Heterogeneity ◽  
Intrinsic Absorption ◽  
Pars Recta ◽  
Intrinsic Capacity ◽  
Control Fluid

Previous investigations have suggested that there is a functional heterogeneity along the length of the proximal convoluted tubule. This study was designed to confirm and extend these suggestions by examining the intrinsic absorption of fluid and the effect of parathyroid hormone (PTH) on net fluid absorption in isolated, anatomically defined segments of rabbit superficial proximal tubules. The EPCT (early proximal convoluted tubule), LPCT (late proximal convoluted tubule), and PR (pars recta) segments were studied under controlled conditions by the isolated perfused tubule technique. In 23 EPCT, base-line fluid absorption was 1.38 +/- 0.04 (SE), a rate significantly higher than those of 11 LPCT (0.62 +/- 0.02; P less than 0.001) and 12 PR (0.52 +/- 0.03 nl mm-1 min-1, P less than 0.001) segments. In 10 EPCT, mean control fluid absorption was 1.31 +/- 0.04 nl mm-1 min-1; addition of PTH resulted in a decrease to 0.95 +/- 0.05 nl mm-1 min-1 (P less than 0.001); and, after removal of PTH, fluid absorption increased (P less than 0.001). Parathyroid hormone had no effect on either seven LPCT segments or six PR segments. These results demonstrate differences in intrinsic capacity to absorb fluid by anatomically defined segments of the rabbit proximal tubule. This functional heterogeneity is further supported by the observed differential response to PTH by the various anatomic segments of the proximal tubule.

Fluid secretion in the nephron: Relation to renal failure

1976 ◽  
Vol 56 (1) ◽  
pp. 248-258 ◽  
Author(s):  
J. J. Grantham
Keyword(s):  
Fluid Transport ◽  
Fluid Secretion ◽  
Cystic Kidney Disease ◽  
Rabbit Kidney ◽  
Cystic Kidney ◽  
Obstructive Nephropathy ◽  
Bathing Medium ◽  
Pars Recta ◽  
Uremic Syndrome

It had been generally accepted that glomerular filtration and tubular reabsorption were the basic modes of fluid transport in mammalian nephrons. Recently, evidence was obtained to indicate that net fluid secretion may occur in mammalian nephrons as well. In the pars recta portion of proximal tubules of rabbit kidney net fluid secretion was observed in vitro in response to PAH and other aryl acids in the peritubular bathing medium. Net fluid secretion appeared to be coupled to the transcellular transport of aryl acid from bath to lumen. Serum from uremic subjects stimulated net fluid secretion in the pars recta in a manner similar to PAH. The accumulation of high levels of endogenous aryl acids may contribute to the general organ dysfunction that is a part of the uremic syndrome of advanced renal insufficiency. Futhermore, there is evidence to suggest that the fluid-secretion phenomenon in association with aryl acids may significantly affect renal excretion and morphology in slow-flow states, in patients with cystic kidney disease, and in obstructive nephropathy.

Increased fluid absorption and cell volume in isolated rabbit proximal straight tubules after in vivo DOCA administration

1981 ◽  
Vol 241 (5) ◽  
pp. F502-F508 ◽  
Author(s):  
M. A. Knepper ◽  
M. B. Burg
Keyword(s):  
Proximal Tubule ◽  
Cell Volume ◽  
Fluid Transport ◽  
Sodium Intake ◽  
Plasma Concentrations ◽  
Dietary Sodium ◽  
Fluid Absorption ◽  
Direct Stimulation ◽  
Stimulation Of

To investigate whether mineralocorticoids affect the intrinsic capacity of the proximal tubule to absorb sodium and fluid, rabbits were chronically treated a number of ways to systematically vary plasma concentrations of mineralocorticoid hormones. The rate of fluid absorption and tubule dimensions were measured in superficial S2 segments from these rabbits. Chronic administration of deoxycorticosterone acetate (DOCA) was associated with a 67% increase in fluid absorption and a 29% increase in cell volume per unit tubule length. However, neither adrenalectomy nor low sodium diet significantly affected either fluid absorption or cell volume. Furthermore, marked dietary sodium restriction prevented the response to DOCA. We conclude that the DOCA-induced increases in fluid absorption and cell volume do not result from a direct stimulation of the proximal tubular cells by the steroid but more likely are responses to systemic effects of DOCA administration that are dependent on the level of sodium intake. Thus, we find no evidence for a direct mineralocorticoid stimulation of sodium and fluid transport by the S2 portion of the proximal tubule.

Calcifediol antagonizes PTH action on water and phosphate absorption in rabbit pars recta

1988 ◽  
Vol 254 (1) ◽  
pp. F45-F50
Author(s):  
R. A. Peraino ◽  
D. Rouse ◽  
W. N. Suki
Keyword(s):  
Parathyroid Hormone ◽  
Chloride Concentration ◽  
Phosphate Transport ◽  
Normal Diet ◽  
Fluid Absorption ◽  
Concentration Difference ◽  
Pars Recta ◽  
Phosphate Flux ◽  
Tubule Fluid ◽  
25 Hydroxycholecalciferol

Reports of the effects of calcifediol (25-hydroxycholecalciferol) on phosphate excretion, alone or with parathyroid hormone (PTH), or with adenosine 3',5'-cyclic monophosphate (cAMP), have been conflicting. The purpose of this investigation was to examine the effects on fluid and phosphate transport by the rabbit pars recta of calcifediol alone or with PTH. In tubule segments obtained from rabbits fed a normal diet, the addition of 10 or 30 nM calcifediol to the bath did not alter fluid absorption (Jv) or lumen-to-bath phosphate flux (JPil----b). However, pharmacological concentrations did inhibit Jv by 20.9 +/- 5.6% (100 nM, P less than 0.02) and 37.9 +/- 9.4% (1.0 microM, P less than 0.01) and JPil----b by 18.5 +/- 6.6% (100 nM, P less than 0.05) and 40.5 +/- 8.6% (1.0 microM, P less than 0.01). In the presence of 30 nM, 100 nM, or 1.0 microM calcifediol, neither 0.25 nor 1.0 U/ml PTH inhibited JPil----b. A modest decline in Jv did occur with 1.0 U/ml PTH in the presence of 30 nM and 100 nM calcifediol. Unlike calcifediol, when 10 nM calcitriol (1,25-dihydroxycholecalciferol) was present in the bath, 0.2 U/ml PTH significantly depressed Jv and JPil----b. To investigate the mechanism of action of high calcifediol concentration, measurement of the collected minus perfused tubule fluid chloride concentration difference was performed.(ABSTRACT TRUNCATED AT 250 WORDS)

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