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.

The effect of sodium taurocholate on proximal tubular reabsorption in the rat kidney

1987 ◽  
Vol 72 (1) ◽  
pp. 139-141 ◽  
Author(s):  
O. S. Better ◽  
V. Guckian ◽  
G. Giebisch ◽  
R. Green
Keyword(s):  
Proximal Tubule ◽  
Bile Salts ◽  
Rat Kidney ◽  
Sodium Taurocholate ◽  
Tubular Reabsorption ◽  
Major Site ◽  
Proximal Tubular ◽  
Tubular Fluid Reabsorption ◽  
Proximal Tubular Reabsorption

1. Microperfusion of tubules in situ was used to study the direct effect of sodium taurocholate on reabsorption of fluid by the proximal tubule of the rat. 2. Sodium taurocholate (0.1 mmol/l) in the tubular perfusate reduced proximal tubular fluid reabsorption by approximately 30%. 3. Thus, the proximal tubule appears to be a major site at which bile salts cause a natriuresis in the rat, and possibly in obstructive jaundice in man.

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.

Posttranscriptional regulation of the proximal tubule NaPi-II transporter in response to PTH and dietary Pi

1999 ◽  
Vol 277 (5) ◽  
pp. F676-F684 ◽  
Author(s):  
Heini Murer ◽  
Ian Forster ◽  
Nati Hernando ◽  
Georg Lambert ◽  
Martin Traebert ◽  
...  
Keyword(s):  
Parathyroid Hormone ◽  
Proximal Tubule ◽  
Posttranscriptional Regulation ◽  
Apical Membrane ◽  
Tubular Reabsorption ◽  
Transport Capacity ◽  
Phosphate Intake ◽  
Proximal Tubular ◽  
Dietary Phosphate ◽  
Proximal Tubular Reabsorption

The rate of proximal tubular reabsorption of phosphate (Pi) is a major determinant of Pi homeostasis. Deviations of the extracellular concentration of Piare corrected by many factors that control the activity of Na-Pi cotransport across the apical membrane. In this review, we describe the regulation of proximal tubule Pi reabsorption via one particular Na-Pi cotransporter (the type IIa cotransporter) by parathyroid hormone (PTH) and dietary phosphate intake. Available data indicate that both factors determine the net amount of type IIa protein residing in the apical membrane. The resulting change in transport capacity is a function of both the rate of cotransporter insertion and internalization. The latter process is most likely regulated by PTH and dietary Pi and is considered irreversible since internalized type IIa Na-Picotransporters are subsequently routed to the lysosomes for degradation.

A Study in Vivo of Peritubular Oncotic Pressure and Proximal Tubular Reabsorption in the Rat

1976 ◽  
Vol 51 (4) ◽  
pp. 379-392 ◽  
Author(s):  
J. D. Conger ◽  
E. Bartoli ◽  
L. E. Earley
Keyword(s):  
Tubular Reabsorption ◽  
Detectable Effect ◽  
Oncotic Pressure ◽  
Peritubular Capillary ◽  
Fluid Reabsorption ◽  
Proximal Tubular ◽  
Convoluted Tubules ◽  
Proximal Tubular Reabsorption ◽  
Tubule Fluid

1. Peritubular capillary microperfusion was used to examine the effects of protein-free and hyperoncotic homologous plasma on fluid reabsorption by proximal convoluted tubules in the hydropenic rat. 3H-labelled p-aminohippurate was added to perfusates for the purpose of estimating the extent to which tubules under study were bathed by the perfusates. [14C]Mannitol was added to perfusates in order to detect contamination of collected tubular fluid by perfusates. 2. Hydrostatic pressures were monitored in the peritubular microvasculature and adjacent proximal tubules during perfusion. Evidence for secretion of p-aminohippurate from perfusate into tubules under study was determined by collecting tubular fluid from both early and late puncture sites. Fractional and absolute reabsorption were not affected by either the protein-free or the hyperoncotic plasma. 3. When acetazolamide was added to the perfusate both fractional and absolute reabsorptive rates decreased by an average of 36%, indicating that the techniques were capable of detecting a decrease in proximal tubular reabsorption. 4. It is concluded that under the conditions of this study changes in peritubular capillary protein concentrations have no detectable effect on the rate of proximal convoluted tubule fluid reabsorption.

A Micropuncture Study of Proximal Tubular Function after Acute Hydrochlorothiazide Administration to Brattleboro Rats with Diabetes Insipidus

1979 ◽  
Vol 57 (5) ◽  
pp. 427-434 ◽  
Author(s):  
S. J. Walter ◽  
J. F. Laycock ◽  
D. G. Shirley
Keyword(s):  
Glomerular Filtration Rate ◽  
Diabetes Insipidus ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Inhibitory Effect ◽  
Tubular Reabsorption ◽  
Brattleboro Rats ◽  
Fluid Reabsorption ◽  
Proximal Tubular ◽  
Proximal Tubular Reabsorption

1. Renal function in anaesthetized Brattleboro rats with hereditary hypothalamic diabetes insipidus was studied with micropuncture techniques before, and 1–3 h after, a single injection of hydrochlorothiazide. 2. In rats given hydrochlorothiazide and kept in sodium and water balance, total glomerular filtration rate and superficial nephron filtration rate were similar to values in control animals, whereas fractional fluid reabsorption in the proximal tubule (as evidenced by tubular fluid/plasma inulin concentration ratios) was slightly, but significantly, reduced. This suggests that hydrochlorothiazide may have a small direct inhibitory effect on proximal tubular reabsorption. 3. When rats were given hydrochlorothiazide and the resultant extra urinary sodium losses were not replaced, there was a marked antidiuresis. In these animals total glomerular filtration rate was reduced by 23% and superficial nephron filtration rate by 27% when compared with values in control rats. Fractional proximal tubular fluid reabsorption increased significantly whereas absolute proximal fluid reabsorption was unaffected. 4. It is concluded that the reduction in body sodium which follows acute hydrochlorothiazide administration over-rides any inhibitory effect of the drug on proximal tubular reabsorption, and leads instead to an increase in fractional fluid reabsorption at this site. This effect, combined with the fall in glomerular filtration rate, results in a greatly reduced delivery of fluid to the more distal nephron segments, and is probably largely responsible for the observed antidiuresis.

Renal tubular uptake of protein: effect of molecular charge

1983 ◽  
Vol 244 (4) ◽  
pp. F436-F441 ◽  
Author(s):  
E. I. Christensen ◽  
H. G. Rennke ◽  
F. A. Carone
Keyword(s):  
Cytochrome C ◽  
Proximal Tubule ◽  
Isoelectric Point ◽  
Tubular Reabsorption ◽  
Molecular Configuration ◽  
Molecular Charge ◽  
Proximal Tubular ◽  
The Difference ◽  
Proximal Tubular Reabsorption

The effect of molecular charge of proteins on proximal tubular reabsorption was evaluated in the rat. Native and two cationized forms of albumin, native and anionized lysozyme, and native and anionized cytochrome c were iodinated with 125I. The different forms of each type of protein were alternately microinfused into the same site of proximal convoluted tubules in vivo. Tubular reabsorption was determined as the difference between the amounts of TCA-precipitable radioactivity infused and recovered in the urine. At low concentration of albumin 5 times more cationized than anionic albumin and 2.7 times more cationic than anionized lysozyme were reabsorbed by the proximal tubule. At two of four concentrations, proximal tubular uptake of cationic cytochrome c exceeded that of anionized cytochrome c. Uptake of cationic cytochrome c exceeded that of cationic lysozyme; however, the difference in uptake between native cationic and anionized species of the two proteins was much greater for lysozyme than for cytochrome c. The data reveal that a higher isoelectric point significantly enhances proximal tubular reabsorption of albumin, lysozyme, and cytochrome c and that proteins with similar molecular weight and isoelectric point are not necessarily reabsorbed to the same degree. This suggests that in addition to total molecular charge the molecular configuration and/or distribution of electrical charges on teh protein surface determine protein binding by the luminal membrane and subsequent endocytosis by the proximal tubule.

Acute arterial hypertension inhibits proximal tubular fluid reabsorption in normotensive rat but not in SHR

2004 ◽  
Vol 286 (4) ◽  
pp. R726-R733 ◽  
Author(s):  
Christopher Walstead ◽  
Kay-Pong Yip
Keyword(s):  
Arterial Hypertension ◽  
Sprague Dawley ◽  
Acute Hypertension ◽  
Continuous Increase ◽  
Spontaneously Hypertensive ◽  
Fluid Reabsorption ◽  
Sprague Dawley Rats ◽  
Proximal Tubular ◽  
Tubular Flow ◽  
Tubular Fluid Reabsorption

The effect of acute arterial hypertension on proximal tubular fluid reabsorption was investigated in Sprague-Dawley rats and spontaneously hypertensive rats (SHR) by measuring proximal tubular flow with a nonobstructive optical method. Under control conditions, spontaneous tubular flow was oscillating at 0.02-0.03 Hz in Sprague-Dawley rats. Acute hypertension induced an immediate increase of mean tubular flow (50% increase after 20 min of hypertension) and augmentation of oscillatory amplitude. Acute hypertension did not alter single-nephron blood flow as measured by laser-Doppler velocimetry ( n = 12), suggesting that the increase of tubular flow was due to inhibition of reabsorption but not increase of filtration. By contrast, spontaneous tubular flow was fluctuating aperiodically in SHR. Acute hypertension did not induce a continuous increase of tubular flow or an increase in amplitude of fluctuations ( n = 15). When apical Na+/H+ exchanger activity of proximal tubule was monitored, acute hypertension did not alter the activity in SHR ( n = 8), while similar procedures had been shown to inhibit apical Na+/H+ exchanger activity of proximal tubules by more than 40% in Sprague-Dawley rats. These observations suggest that acute hypertension inhibits proximal tubular fluid reabsorption by inhibiting apical Na+/H+ exchanger activity in Sprague-Dawley rats and that this mechanism is impaired in SHR.

Homeostatic efficiency of tubuloglomerular feedback is reduced in established diabetes mellitus in rats

1995 ◽  
Vol 269 (6) ◽  
pp. F876-F883 ◽  
Author(s):  
V. Vallon ◽  
R. C. Blantz ◽  
S. Thomson
Keyword(s):  
Streptozotocin Diabetes ◽  
Diabetic Rats ◽  
Tubular Reabsorption ◽  
Tubuloglomerular Feedback ◽  
Ambient Flow ◽  
Proximal Tubular ◽  
On Line ◽  
Tubular Flow ◽  
A Minor ◽  
Proximal Tubular Reabsorption

We tested the hypothesis that the ability of the tubuloglomerular feedback (TGF) to stabilize renal function is impaired in rats with 7-8 wk of insulin-treated streptozotocin-diabetes. Proximal tubular flow was measured in free-flowing nephrons using a noninvasive optical technique. The homeostatic efficiency of TGF was determined from the fractional compensation for perturbations in ambient flow. Fractional compensation was substantially reduced in diabetic rats. To assess the roles of the proximal tubule and loop of Henle as determinants of TGF efficiency, we tested the effect of diabetes on proximal tubular reabsorption as determined by standard micropuncture and on the ionic content of early distal tubular fluid by employing a microelectrode for on-line measurement of electrical conductivity (TED). Diabetes caused glomerular hyperfiltration and increased fractional proximal tubular reabsorption (FPR), such that late proximal tubular flow (VLP) and early distal tubular flow were unaffected. The increase in FPR was a minor contributor to the overall effect on fractional compensation. Diabetes decreased the ambient TED without affecting the slope of the relationship between VLP and TED. These results demonstrate that the homeostatic, efficiency of the TGF system is reduced in diabetes and that this cannot be fully accounted for by changes in tubular reabsorption. Impaired TGF efficiency renders the diabetic glomerular microvasculature more susceptible to impact from fluctuations in systemic hemodynamics.

Identification of a Delivery-Related Influence on Proximal Tubular Reabsorption during Expansion with Hyperoncotic Albumin in the Rat

1978 ◽  
Vol 55 (4) ◽  
pp. 369-376
Author(s):  
J. F. Donohoe ◽  
Gertrude S. Lefavour ◽  
S. Cortell ◽  
F. J. Gennari
Keyword(s):  
Fluid Flow ◽  
Flow Rate ◽  
Filtration Rate ◽  
Perfusion Pressure ◽  
Renal Perfusion ◽  
Tubular Reabsorption ◽  
Renal Perfusion Pressure ◽  
Proximal Tubular ◽  
Tubular Flow ◽  
Proximal Tubular Reabsorption

1. Proximal tubular fluid flow rate was deliberately reduced to control values in rats after acute volume expansion with hyperoncotic albumin, to determine if the depression of reabsorption by albumin-induced expansion could be uncovered by preventing the associated increase in filtrate delivery. Tubular fluid flow was reduced either by reducing renal perfusion pressures or by diverting fluid from early proximal tubular sites. 2. In the absence of controlled delivery, expansion with hyperoncotic albumin increased nephron filtration rate, reduced the TF/P inulin ratio, but had no effect on absolute reabsorptive rate. When proximal tubular flow rate was returned to control values by a simultaneous early collection, fractional reabsorption remained depressed. By contrast, when tubular flow was maintained at control values by reducing renal perfusion pressure, the large fall in fractional reabsorption was blocked. 3. The results indicate that expansion with hyperoncotic albumin depresses proximal tubular reabsorption independently of delivery rate into the proximal tubule, but that this effect can be reversed by a reduction in renal perfusion pressure. These observations unify the results of previous studies and indicate the presence of a delivery-related influence on proximal reabsorption. The inability to detect a reduction in absolute reabsorption when nephron filtration rate is increased during expansion with hyperoncotic albumin is probably due to the countervailing influence of increased delivery rate, which raised reabsorptive rate.

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