Phosphate uptake by a kidney cell line (LLC-PK1)

1983 ◽  
Vol 245 (1) ◽  
pp. F22-F31 ◽  
Author(s):  
C. A. Rabito
Keyword(s):  
Cell Line ◽  
Transport System ◽  
Apical Membrane ◽  
Phosphate Uptake ◽  
Phosphate Transport ◽  
Epithelial Cell Line ◽  
Proximal Tubular ◽  
Independent Process ◽  
Uptake Studies ◽  
Renal Origin

The uptake of inorganic phosphate was studied in an epithelial cell line of renal origin. Phosphate was accumulated through a mechanism with several features of a carrier-mediated process. The influx was accounted for by a saturable Na+-dependent and a nonsaturable Na+-independent process. Kinetic analysis at pH 6.6 and 7.4 suggests that the dibasic form of phosphate is the form transported by the saturable Na+-dependent system. The presence of Na+ in the incubation medium increased Vmax without affecting Km. Arsenate competitively inhibited the Na+-dependent phosphate transport with a Ki of 1.2 mM at 140 mM Na+ and pH 7.4. Other known inhibitors of phosphate reabsorption in the proximal tubule also inhibited phosphate transport by this cell line. Uptake studies from either side of the monolayers indicated that this transport system is preferentially located in the apical membrane of the cultured renal cells. These results show a close similarity between the Na+-dependent phosphate transport system in LLC-PK1 cells and the system present in the apical membrane of the proximal tubular cells.

Sodium-dependent transport of Pi by an established intestinal epithelial cell line (CaCo-2)

1986 ◽  
Vol 250 (3) ◽  
pp. G323-G330 ◽  
Author(s):  
I. Mohrmann ◽  
M. Mohrmann ◽  
J. Biber ◽  
H. Murer
Keyword(s):  
Cell Line ◽  
Transport System ◽  
Apical Membrane ◽  
Intestinal Cell ◽  
Epithelial Cell Line ◽  
Maximal Velocity ◽  
Intact Cells ◽  
High Sodium ◽  
Sodium Dependent ◽  
Dependent Transport

The uptake of inorganic phosphate (Pi) was analyzed in monolayers and in apical membrane vesicles (AMV) of the established intestinal cell line CaCo-2. AMV, prepared by a MgCl2 precipitation technique, were enriched approximately 10-fold in alkaline phosphatase activity. Pi uptake into intact cells as well as into AMV was specifically dependent on the presence of sodium. In the presence of high sodium concentrations, the apparent Km for Pi was 214 +/- 17 mumol/l in monolayers and 300 +/- 19.7 mumol/l in AMV. Increasing the sodium concentration increased the apparent affinity of the transport system for Pi but hardly affected the maximal velocity (Vmax). At 0.1 mmol/l Pi and pH 7.4, the apparent Km for sodium was approximately 70 mmol/l in intact cells as well as in AMV. The results obtained in both systems suggested the involvement of two sodium ions and one phosphate ion in the transport process. Advancing confluence--independently of the age of the monolayers--reduced sodium-dependent uptake of Pi significantly by a decrease in Vmax, whereas the apparent Km for Pi remained unchanged. It is concluded that the apical membrane of CaCo-2 cells contains a sodium-dependent transport system for Pi.

Phosphate uptake by renal membrane vesicles of rabbits adapted to high and low phosphorus diets

1983 ◽  
Vol 245 (2) ◽  
pp. F175-F180 ◽  
Author(s):  
L. Cheng ◽  
C. T. Liang ◽  
B. Sacktor
Keyword(s):  
Transport System ◽  
Phosphate Uptake ◽  
Membrane Vesicles ◽  
Phosphate Transport ◽  
Uptake System ◽  
Low Phosphorus ◽  
Dietary Phosphate ◽  
Preferred Species ◽  
Uptake Medium ◽  
Phosphate Carrier

Renal adaptation to changes in phosphate intake was studied by comparing phosphate uptake by proximal tubule brush border membrane vesicles from rabbits on a relatively high or low phosphorus diet. The low phosphorus diet increased Na+ gradient-dependent phosphate uptake. Uptake in the absence of Na+ and in the presence of Na+, but no gradient, was not significantly affected. The phosphorus diet did not alter Na+ gradient-dependent D-glucose and L-proline uptake. The low phosphorus diet increased Vmax; affinity for phosphate was not appreciably changed. At all concentrations of extravesicular Na+, phosphate uptake was higher in membrane vesicles from animals fed the low phosphorus diet; the kinetics of the phosphate uptake system, with respect to Na+, was also altered by the change in dietary phosphate. These findings suggest that adaptation involves an alteration in the rate of translocation of the Na+-phosphate carrier when energized by a Na+ gradient driving force rather than a change in the number of Na+-phosphate carrier sites. With membrane vesicles from rabbits fed a low phosphorus diet, phosphate uptake increased several-fold when the pH of the uptake medium was raised, whereas with membrane vesicles from animals fed a high phosphorus diet the enhancement of uptake with alkalinization was relatively small. Irrespective of the diet, divalent phosphate was the probable preferred species for transport. Dietary adaptation was associated, however, with an alteration in the pH dependency of the transport system per se. These findings provide evidence that the adaptation of the kidney phosphate transport system to dietary phosphate load involves an intrinsic change in the Na+-phosphate carrier.

scholarly journals CG200745, a Novel HDAC Inhibitor, Attenuates Kidney Fibrosis in a Murine Model of Alport Syndrome

2020 ◽  
Vol 21 (4) ◽  
pp. 1473
Author(s):  
Sang Heon Suh ◽  
Hong Sang Choi ◽  
Chang Seong Kim ◽  
In Jin Kim ◽  
Hyunju Cha ◽  
...  
Keyword(s):  
Angiotensin Ii ◽  
Cell Line ◽  
Murine Model ◽  
Alport Syndrome ◽  
Transforming Growth Factor ◽  
Rat Kidney ◽  
Epithelial Cell Line ◽  
Tgfβ Signaling ◽  
Kidney Fibrosis ◽  
Proximal Tubular

Histone deacetylases have been a target of therapy for organ fibrosis. Here, we report the protective effect of CG200745 (CG), a novel histone deacetylase inhibitor, on tubulointerstitial fibrosis in Col4a3−/− mice, a murine model of Alport syndrome. Morphological analyses revealed CG treatment markedly alleviated kidney fibrosis in Col4a3−/− mice at the age of 7 weeks. CG prevented the activation of transforming growth factor β (TGFβ) and its downstream SMAD signaling in the kidney of Col4a3−/− mice. As critical upstream regulators of TGFβ signaling, immunoblotting of whole kidney lysate of Col4a3−/− mice reveled that intra-renal renin–angiotensin system (RAS) was activated with concurrent upregulation of inflammation and apoptosis, which were effectively suppressed by CG treatment. CG suppressed both activation of RAS and up-regulation of TGFβ signals in angiotensin II-stimulated HK-2 cells, a human kidney proximal tubular epithelial cell line. CG inhibited activation of TGFβ-driven signals and fibrosis in NRK-49F cells, a rat kidney fibroblast cell line, under angiotensin II-rich conditions. Collectively, CG was found to be effective both in proximal tubular epithelial cells by inhibiting local RAS and TGFβ signaling activation, as well as in fibroblasts by blocking their transition to myofibroblasts, attenuating renal fibrosis in a murine model of Alport syndrome.

scholarly journals Conditionally immortalized human proximal tubular epithelial cells isolated from the urine of a healthy subject express functional calcium-sensing receptor

2015 ◽  
Vol 308 (11) ◽  
pp. F1200-F1206 ◽  
Author(s):  
Annarita Di Mise ◽  
Grazia Tamma ◽  
Marianna Ranieri ◽  
Maria Svelto ◽  
Bert van den Heuvel ◽  
...  
Keyword(s):  
Healthy Subject ◽  
Cell Line ◽  
Cell Lines ◽  
Cyclopiazonic Acid ◽  
Cytosolic Calcium ◽  
Epithelial Cell Line ◽  
Loss Of Function ◽  
Calcium Sensing Receptor ◽  
Calcium Sensing ◽  
Proximal Tubular

The calcium-sensing receptor (CaSR) is a G protein-coupled receptor, which plays an essential role in regulating Ca2+ homeostasis. Here we show that conditionally immortalized proximal tubular epithelial cell line (ciPTEC) obtained by immortalizing and subcloning cells exfoliated in the urine of a healthy subject expresses functional endogenous CaSR. Immunolocalization studies of polarized ciPTEC revealed the apical localization of the receptor. By Western blotting of ciPTEC lysates, both monomeric and dimeric forms of CaSR at 130 and ∼250 kDa, respectively, were detected. Functional studies indicated that both external calcium and the positive CaSR allosteric modulator, NPS-R568, induced a significant increase in cytosolic calcium, proving a high sensitivity of the endogenous receptor to its agonists. Calcium depletion from the endoplasmic reticulum using cyclopiazonic acid abolished the increase in cytosolic calcium elicited by NPS-R568, confirming calcium exit from intracellular stores. Activation of CaSR by NPS-R significantly reduced the increase in cAMP elicited by forskolin (FK), a direct activator of adenylate cyclase, further confirming the functional expression of the receptor in this cell line. CaSR expressed in ciPTEC was found to interact with Gq as a downstream effector, which in turn can cause release of calcium from intracellular stores via phospholipase C activation. We conclude that human proximal tubular ciPTEC express functional CaSR and respond to its activation with a release of calcium from intracellular stores. These cell lines represent a valuable tool for research into the disorder associated with gain or loss of function of the CaSR by producing cell lines from patients.

Sign in / Sign up

Export Citation Format

Share Document