scholarly journals Effects of dietary Pi on the renal Na+-dependent Pi transporter NaPi-2 in thyroparathyroidectomized rats

1998 ◽  
Vol 333 (1) ◽  
pp. 175-181 ◽  
Author(s):  
Fumie TAKAHASHI ◽  
Kyoko MORITA ◽  
Kanako KATAI ◽  
Hiroko SEGAWA ◽  
Ai FUJIOKA ◽  
...  
Keyword(s):  
Parathyroid Hormone ◽  
Proximal Tubule ◽  
Immunohistochemical Analysis ◽  
Renal Proximal Tubule ◽  
Kidney Cortex ◽  
Transport Activity ◽  
Independent Manner ◽  
Pi Transport

Dietary Pi and parathyroid hormone (PTH) are two most important physiological and pathophysiological regulators of Pi re-absorption in the renal proximal tubule. Effects of dietary Pi on Na+/Pi co-transporter NaPi-2 were investigated in thyroparathyroidectomized (TPTX) rats. NaPi-2 protein and mRNA in the kidney cortex of TPTX rats were increased ≈ 3.8- and 2.4-fold in amount respectively compared with those in the sham-operated animals. Administration of PTH to the TPTX rats resulted in a decrease in the amount of NaPi-2 protein, but not in the abundance of NaPi-2 mRNA. Deprivation of dietary Pi in the TPTX rats did not affect the amount of NaPi-2 mRNA and protein. In the Pi-deprived TPTX rats, feeding of a high-Pi diet resulted in marked decreases in Pi transport activity and the amount of NaPi-2 protein in the superficial nephrons. Immunohistochemical analysis demonstrated that administration of PTH to TPTX rats resulted in a decrease in NaPi-2 immunoreactivity from both superficial and juxtamedullary nephrons within 4 h. Switching TPTX animals from a low-Pi diet to the high-Pi diet decreased NaPi-2 immunoreactivity from superficial nephrons, but not from juxtamedullary nephrons, within 4 h. These results suggest that dietary Pi could regulate the amount of NaPi-2 protein in the superficial nephrons in a PTH-independent manner.

Hormonal regulation of rat renal proximal tubule brush-border membrane ionic permeability

1992 ◽  
Vol 263 (1) ◽  
pp. F144-F151 ◽  
Author(s):  
M. S. Lipkowitz ◽  
R. D. London ◽  
J. C. Beck ◽  
R. G. Abramson
Keyword(s):  
Parathyroid Hormone ◽  
Proximal Tubule ◽  
Brush Border ◽  
Renal Proximal Tubule ◽  
Ionic Permeability ◽  
Brush Border Membranes ◽  
Rat Renal Proximal Tubule ◽  
Selective Increase ◽  
Gi Proteins ◽  
Cl Permeability

The effects on ionic permeability of toxins and hormones that activate or deactivate the guanine nucleotide regulatory (G) proteins that govern adenylate cyclase activity were examined in rat renal proximal tubule cell brush-border membranes. These studies demonstrate that activation of stimulatory G (Gs) proteins by cholera toxin or parathyroid hormone and deactivation of inhibitory (G (Gi) proteins by pertussis toxin result in a selective increase in Cl- permeability relative to that of K+ as determined with the potential-sensitive fluorescent probe 3,3'-dipropylthiadicarbocyanine iodide [diS-C3-(5)]. In contrast, activation of Gi by angiotensin II significantly decreases relative Cl- permeability. The selective increase in relative Cl- permeability induced by parathyroid hormone results in an inside-negative potential in membrane vesicles exposed to an inward NaCl gradient that is of sufficient magnitude to stimulate electrogenic, Na(+)-dependent glucose transport. These data suggest that the relative ionic permeabilities of brush-border membranes are tonically regulated by the opposing effects of hormones that act via Gs or Gi proteins. Changes in membrane potential resulting from this regulation may play an important role in modifying transport in the proximal tubule.

scholarly journals Defective Parathyroid Hormone Regulation of NHE3 Activity and Phosphate Adaptation in Cultured NHERF-1-/-Renal Proximal Tubule Cells

2004 ◽  
Vol 279 (36) ◽  
pp. 37815-37821 ◽  
Author(s):  
Rochelle Cunningham ◽  
Deborah Steplock ◽  
Fengying Wang ◽  
Huijun Huang ◽  
Xiaofei E ◽  
...  
Keyword(s):  
Parathyroid Hormone ◽  
Proximal Tubule ◽  
Renal Proximal Tubule ◽  
Hormone Regulation ◽  
Proximal Tubule Cells ◽  
Tubule Cells ◽  
Renal Proximal Tubule Cells

scholarly journals Transgenic Overexpression of the Extra-Large Gsα Variant XLαs Enhances Gsα-Mediated Responses in the Mouse Renal Proximal Tubule in Vivo

Endocrinology ◽  
2011 ◽  
Vol 152 (4) ◽  
pp. 1222-1233 ◽  
Author(s):  
Zun Liu ◽  
Hiroko Segawa ◽  
Cumhur Aydin ◽  
Monica Reyes ◽  
Reinhold G. Erben ◽  
...  
Keyword(s):  
Proximal Tubule ◽  
Immunohistochemical Analysis ◽  
Renal Proximal Tubule ◽  
Mrna Levels ◽  
Wild Type ◽  
Western Blots ◽  
Α Subunit ◽  
Exon 1 ◽  
Serum Pth

Abstract XLαs, a variant of the stimulatory G protein α-subunit (Gsα), can mediate receptor-activated cAMP generation and, thus, mimic the actions of Gsα in transfected cells. However, it remains unknown whether XLαs can act in a similar manner in vivo. We have now generated mice with ectopic transgenic expression of rat XLαs in the renal proximal tubule (rptXLαs mice), where Gsα mediates most actions of PTH. Western blots and quantitative RT-PCR showed that, while Gsα and type-1 PTH receptor levels were unaltered, protein kinase A activity and 25-hydroxyvitamin D 1-α-hydroxylase (Cyp27b1) mRNA levels were significantly higher in renal proximal tubules of rptXLαs mice than wild-type littermates. Immunohistochemical analysis of kidney sections showed that the sodium-phosphate cotransporter type 2a was modestly reduced in brush border membranes of male rptXLαs mice compared to gender-matched controls. Serum calcium, phosphorus, and 1,25 dihydroxyvitamin D were within the normal range, but serum PTH was ∼30% lower in rptXLαs mice than in controls (152 ± 16 vs. 222 ± 41 pg/ml; P < 0.05). After crossing the rptXLαs mice to mice with ablation of maternal Gnas exon 1 (E1m−/+), male offspring carrying both the XLαs transgene and maternal Gnas exon 1 ablation (rptXLαs/E1m−/+) were significantly less hypocalcemic than gender-matched E1m−/+ littermates. Both E1m−/+ and rptXLαs/E1m−/+ offspring had higher serum PTH than wild-type littermates, but the degree of secondary hyperparathyroidism tended to be lower in rptXLαs/E1m−/+ mice. Hence, transgenic XLαs expression in the proximal tubule enhanced Gsα-mediated responses, indicating that XLαs can mimic Gsα in vivo.

Effect of parathyroid hormone on acid/base transport in rabbit renal proximal tubule S3 segment

1993 ◽  
Vol 423-423 (1-2) ◽  
pp. 7-13 ◽  
Author(s):  
George Seki ◽  
Shigeo Taniguchi ◽  
Shu Uwatoko ◽  
Keiji Suzuki ◽  
Kiyoshi Kurokawa
Keyword(s):  
Parathyroid Hormone ◽  
Proximal Tubule ◽  
Renal Proximal Tubule ◽  
Acid Base ◽  
S3 Segment

scholarly journals Local pH domains regulate NHE3-mediated Na+ reabsorption in the renal proximal tubule

2014 ◽  
Vol 307 (11) ◽  
pp. F1249-F1262 ◽  
Author(s):  
Jens Christian Brasen ◽  
James L. Burford ◽  
Alicia A. McDonough ◽  
Niels-Henrik Holstein-Rathlou ◽  
Janos Peti-Peterdi
Keyword(s):  
Blood Pressure ◽  
Proximal Tubule ◽  
Brush Border ◽  
Renal Proximal Tubule ◽  
Kidney Cortex ◽  
Proximal Tubule Cell ◽  
Rat Kidney Cortex ◽  
Pressure Natriuresis ◽  
Local Ph

The proximal tubule Na+/H+ exchanger 3 (NHE3), located in the apical dense microvilli (brush border), plays a major role in the reabsorption of NaCl and water in the renal proximal tubule. In response to a rise in blood pressure NHE3 redistributes in the plane of the plasma membrane to the base of the brush border, where NHE3 activity is reduced. This NHE3 redistribution is assumed to provoke pressure natriuresis; however, it is unclear how NHE3 redistribution per se reduces NHE3 activity. To investigate if the distribution of NHE3 in the brush border can change the reabsorption rate, we constructed a spatiotemporal mathematical model of NHE3-mediated Na+ reabsorption across a proximal tubule cell and compared the model results with in vivo experiments in rats. The model predicts that when NHE3 is localized exclusively at the base of the brush border, it creates local pH microdomains that reduce NHE3 activity by >30%. We tested the model's prediction experimentally: the rat kidney cortex was loaded with the pH-sensitive fluorescent dye BCECF, and cells of the proximal tubule were imaged in vivo using confocal fluorescence microscopy before and after an increase of blood pressure by ∼50 mmHg. The experimental results supported the model by demonstrating that a rise of blood pressure induces the development of pH microdomains near the bottom of the brush border. These local changes in pH reduce NHE3 activity, which may explain the pressure natriuresis response to NHE3 redistribution.

The Fine Structure of Rat Renal Microbodies and Cytoplasmic Bodies Following Perfusion Fixation

1973 ◽  
Vol 31 ◽  
pp. 620-621
Author(s):  
J. M. Barrett ◽  
P. M. Heidger
Keyword(s):  
Fine Structure ◽  
Proximal Tubule ◽  
Rat Kidney ◽  
Renal Proximal Tubule ◽  
Convincing Evidence ◽  
Cytoplasmic Bodies ◽  
Rat Renal Proximal Tubule ◽  
Renal Proximal Tubule Cells ◽  
Perfusion Fixation

Microbodies have received extensive morphological and cytochemical investigation since they were first described by Rhodin in 1954. To our knowledge, however, all investigations of microbodies and cytoplasmic bodies of rat renal proximal tubule cells have employed immersion fixation. Tisher, et al. have shown convincing evidence of fine structural alteration of microbodies in rhesus monkey kidney following immersion fixation; these alterations were not encountered when in vivo intravascular perfusion was employed. In view of these studies, and the fact that techniques for perfusion fixation have been established specifically for the rat kidney by Maunsbach, it seemed desirable to employ perfusion fixation to study the fine structure and distribution of microbodies and cytoplasmic bodies within the rat renal proximal tubule.

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