Proximal tubular reabsorption of some organic acids in the rat kidney in vivo

1965 ◽  
Vol 286 (2) ◽  
pp. 171-180 ◽  
Author(s):  
Harald Sonnenberg ◽  
Hellmut Oelert ◽  
Karl Baumann
Keyword(s):  
Organic Acids ◽  
Rat Kidney ◽  
Tubular Reabsorption ◽  
Proximal Tubular ◽  
Proximal Tubular Reabsorption

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.

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.

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.

Luminal and contraluminal action of 1–34 and 3–34 PTH peptides on renal type IIa Na-Pi cotransporter

2000 ◽  
Vol 278 (5) ◽  
pp. F792-F798 ◽  
Author(s):  
Martin Traebert ◽  
Harald Völkl ◽  
Jürg Biber ◽  
Heini Murer ◽  
Brigitte Kaissling
Keyword(s):  
Brush Border Membrane ◽  
Rat Kidney ◽  
Membrane Domains ◽  
Calphostin C ◽  
Signaling Mechanisms ◽  
Proximal Tubular ◽  
Proximal Tubular Reabsorption ◽  
Dependent Mechanism

Parathyroid hormone (PTH) inhibits proximal tubular reabsorption of Pi by retrieval of type IIa Na-Pi cotransporters (NaPi-IIa) from the brush-border membrane (BBM). We analyzed by immunohistochemistry whether PTH analogs, signaling through either protein kinase A (PKA) and C (PKC; 1–34 PTH) or only PKC (3–34 PTH), elicit in rat kidney in vivo or in the perfused murine proximal tubule in vitro a retrieval of NaPi-IIa and whether pharmacological agonists or inhibitors of these kinases are able to either mimic or interfere with these PTH effects. Treatment with either 1–34 or 3–34 PTH downregulated NaPi-IIa in rat kidney. In isolated murine proximal tubules 1–34 PTH was effective when added to either the apical or basolateral perfusate, whereas 3–34 PTH acted only via the luminal perfusate. These effects were mimicked by an activation of PKA with 8-bromoadenosine 3′,5′-cyclic monophosphate or PKC with 1,2-dioctanoylglycerol. The luminal action of both PTH peptides was blocked by inhibition of the PKC pathway (calphostin C), whereas the basolateral effect of 1–34 PTH was completely abolished by inhibiting both pathways (H-89 and calphostin C). These results suggest that 1) NaPi-IIa can be internalized by cAMP-dependent and -independent signaling mechanisms; 2) functional PTH receptors are located in both membrane domains; and 3) apical PTH receptors may preferentially initiate the effect through a PKC-dependent mechanism.

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