scholarly journals Ionic requirements of proximal tubular fluid reabsorption: Flow dependence of fluid transport

1981 ◽  
Vol 20 (5) ◽  
pp. 580-587 ◽  
Author(s):  
R. Green ◽  
R.J. Moriarty ◽  
Gerhard Giebisch
Keyword(s):  
Fluid Transport ◽  
Fluid Reabsorption ◽  
Flow Dependence ◽  
Proximal Tubular ◽  
Tubular Fluid Reabsorption

Role of luminal hydrostatic pressure in proximal tubular fluid reabsorption in the rat

1975 ◽  
Vol 229 (3) ◽  
pp. 813-819 ◽  
Author(s):  
A Grandchamp ◽  
Scherrer ◽  
D Scholer ◽  
J Bornand
Keyword(s):  
Hydrostatic Pressure ◽  
Proximal Tubule ◽  
Pressure Difference ◽  
Unit Area ◽  
Rat Kidney ◽  
Fluid Reabsorption ◽  
Proximal Tubular ◽  
Tubular Fluid Reabsorption ◽  
Selective Change

The effect of small changes in intraluminal hydrostatic pressure (P) on the tubular radius (r) and the net fluid reabsorption per unit of surface area of the tubular wall (Js) has been studied in the proximal tubule of the rat kidney. The split-drop method was used to simultaneously determine Js and r. Two standardized split-drop techniques A and B allow selective change in P. P was 31.6 +/- 1.3 mmHg in technique A and 15.5 +/- 1.5 in technique B. The pressure difference significantly affected the tubular radius; r was 21.9 +/- 0.4 and 18.6 +/- 0.5 mum in the split drop A and B, respectively. In contrast, net transepithelial fluid reabsorption Js was unchanged. Js amounted to 2.72 +/- 0.20, and 2.78 +/- 0.33 10(-5) cm3 cm-2 s-1 in split drop A and B. The absence of variations in Js could result from two opposite effects of pressure. P might enhance Js by increased ultrafiltration. However, the rise in r might decrease the density of the intraepithelial transport paths per unit area of tubular wall and therefore might decrease Js.

Flash photolysis of caged nitric oxide inhibits proximal tubular fluid reabsorption in free-flow nephron

2005 ◽  
Vol 289 (2) ◽  
pp. R620-R626 ◽  
Author(s):  
Kay-Pong Yip
Keyword(s):  
Nitric Oxide ◽  
Proximal Tubule ◽  
Flash Photolysis ◽  
Tubular Reabsorption ◽  
Fluid Reabsorption ◽  
Proximal Tubular ◽  
Tubular Flow ◽  
Tubular Fluid Reabsorption ◽  
Reabsorption Rate ◽  
Proximal Tubular Reabsorption

A nonobstructing optical method was developed to measure proximal tubular fluid reabsorption in rat nephron at 0.25 Hz. The effects of uncaging luminal nitric oxide (NO) on proximal tubular reabsorption were investigated with this method. Proximal fluid reabsorption rate was calculated as the difference of tubular flow measured simultaneously at two locations (0.8–1.8 mm apart) along a convoluted proximal tubule. Tubular flow was estimated on the basis of the propagating velocity of fluorescent dextran pulses in the lumen. Changes in local tubular flow induced by intratubular perfusion were detected simultaneously along the proximal tubule, indicating that local tubular flow can be monitored in multiple sites along a tubule. The estimated tubular reabsorption rate was 5.52 ± 0.38 nl·min−1·mm−1 ( n = 20). Flash photolysis of luminal caged NO (potassium nitrosylpentachlororuthenate) was induced with a 30-Hz UV nitrogen-pulsed laser. Release of NO from caged NO into the proximal tubule was confirmed by monitoring intracellular NO concentration using a cell-permeant NO-sensitive fluorescent dye (DAF-FM). Emission of DAF-FM was proportional to the number of laser pulses used for uncaging. Photolysis of luminal caged NO induced a dose-dependent inhibition of proximal tubular reabsorption without activating tubuloglomerular feedback, whereas uncaging of intracellular cGMP in the proximal tubule decreased tubular flow. Coupling of this novel method to measure reabsorption with photolysis of caged signaling molecules provides a new paradigm to study tubular reabsorption with ambient tubular flow.

Proximal tubular Na, Cl, and HCO3 reabsorption and renal oxygen consumption

1984 ◽  
Vol 247 (1) ◽  
pp. F151-F157 ◽  
Author(s):  
S. W. Weinstein ◽  
R. Klose ◽  
J. Szyjewicz
Keyword(s):  
Oxygen Consumption ◽  
Ion Transport ◽  
Rat Kidney ◽  
Fluid Reabsorption ◽  
Bicarbonate Reabsorption ◽  
Renal Oxygen Consumption ◽  
Proximal Tubular ◽  
Tubular Fluid Reabsorption ◽  
Renal Oxygen

The majority of the oxygen consumed by the rat kidney appears to occur in the proximal tubule. Therefore changes in metabolically linked ion transport in this segment of the nephron should result in changes in renal oxygen consumption. To study the role of bicarbonate reabsorption in metabolically linked proximal tubular ion transport a series of micropuncture-clearance-extraction experiments were performed comparing the effects of the carbonic anhydrase inhibitor benzolamide and of hypertonic sodium bicarbonate infusion with control conditions in the rat. End-proximal tubular fluid and chloride reabsorption were measured. From these, the rates of sodium and bicarbonate reabsorption were estimated. Simultaneously with the tubular fluids, extraction collections were obtained for determination of renal oxygen consumption. Both benzolamide and hypertonic bicarbonate reduced proximal tubular fluid reabsorption while concomitantly reducing the transepithelial gradient for chloride. The mean rate of renal oxygen consumption did not differ from the control rate in either experimental group and could be dissociated from the calculated net rates of proximal tubular sodium, chloride, and bicarbonate reabsorption. We interpret these data as evidence that proximal tubular hydrogen ion secretion supporting bicarbonate reabsorption requires at most small amounts of oxidative energy, less than detectable by these techniques. The data, in contrast, support the conclusion that the chloride-bicarbonate transepithelial gradient appears to be an important passive driving force in vivo for proximal tubular fluid reabsorption.

Effect of angiotensin II receptor blockade on proximal tubular fluid reabsorption

1997 ◽  
Vol 273 (2) ◽  
pp. R510-R517 ◽  
Author(s):  
P. P. Leyssac ◽  
F. M. Karlsen ◽  
N. H. Holstein-Rathlou
Keyword(s):  
Angiotensin Ii ◽  
Flow Rate ◽  
Feedback Mechanism ◽  
Tubuloglomerular Feedback ◽  
Sprague Dawley ◽  
Angiotensin Ii Receptor ◽  
Fluid Reabsorption ◽  
Nacl Concentration ◽  
Proximal Tubular ◽  
Tubular Fluid Reabsorption

The effect of physiological concentrations of angiotensin II on proximal tubular fluid reabsorption remains controversial. To investigate the effect of blockade of intratubular AT1 receptors on tubular reabsorption, losartan (10(-5) M) was administered by microperfusion into an early proximal convolution of halothane-anesthetized Sprague-Dawley rats. Four parameters that depend on the rate of proximal fluid reabsorption were measured: proximal intratubular pressure (Pprox), early and late proximal flow rate, and early distal NaCl concentration. Pprox decreased by 0.5 +/- 0.1 mmHg, late proximal flow rate decreased by 2.0 +/- 0.8 nl/min, and early distal NaCl concentration decreased by 4.3 +/- 0.8 mM (mean +/- SE). No changes were observed after microperfusion with saline. Because the tubuloglomerular feedback mechanism was operating in the closed-loop mode, the decreased NaCl load to the macula densa will be compensated by an increase in the single-nephron glomerular filtration rate. In agreement with this, the early proximal flow rate, measured proximal to the site of losartan administration, increased by 5.7 +/- 1.3 nl/min. The increase in the rate of proximal reabsorption between the early and late proximal convolutions was estimated to be 7.8 nl/min (approximately 36%). It is concluded that a decrease in local luminal angiotensin II levels and/or AT1 receptor activity under free flow conditions increases the rate of proximal tubular fluid reabsorption.

Evidence for Angiotensin-Stimulated Proximal Tubular Fluid Reabsorption in Normotensive and Hypertensive Rats: Effect of Acute Administration of Captopril

1984 ◽  
Vol 66 (5) ◽  
pp. 541-544 ◽  
Author(s):  
P. J. Harris ◽  
L. G. Navar ◽  
D. W. Ploth
Keyword(s):  
Blood Pressure ◽  
Arterial Blood Pressure ◽  
Acute Administration ◽  
Fluid Absorption ◽  
Hypertensive Rats ◽  
Fluid Reabsorption ◽  
Arterial Blood ◽  
Proximal Tubular ◽  
Tubular Fluid Reabsorption ◽  
Anaesthetized Rat

1. The effects of captopril on mean arterial blood pressure and proximal tubular fluid re-absorption (Jv) were examined in anaesthetized normotensive rats and in the non-clipped kidneys of two-kidney, one-clip Goldblatt hypertensive rats. 2. In the normotensive animals, captopril reduced arterial blood pressure from 121 ± sd 9 to 106 ± 10 mmHg and Jv decreased from 3.78 ± 0.45 to 2.57 ± 0.58 × 10−4mm3mm−2s−1. Captopril had a greater effect on blood pressure in the hypertensive animals (172 ± 17 reduced to 133 ± 23 mmHg) although the decrease in Jv from 3.62 ± 0.12 to 2.40 ± 0.40 was similar to that observed in normotensive animals. 3. These results provide evidence that, in the anaesthetized rat, angiotensin II contributes to the maintenance of the rate of proximal fluid re-absorption. The magnitude of the angiotensin-stimulated component of proximal fluid absorption is similar in normotensive and two-kidney, one-clip Goldblatt hypertensive rats.

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