Kinetics of receptor-mediated endocytosis of albumin in cells derived from the proximal tubule of the kidney (opossum kidney cells): influence of Ca2+ and cAMP

1995 ◽  
Vol 430 (3) ◽  
pp. 374-380 ◽  
Author(s):  
Ruth Freudinger ◽  
Stefen Silbernagl ◽  
Michel Gekle ◽  
Sigrid Mildenberger
Keyword(s):  
Proximal Tubule ◽  
Kidney Cells ◽  
Opossum Kidney ◽  
Receptor Mediated Endocytosis ◽  
Opossum Kidney Cells ◽  
Kinetics Of ◽  
In Cells

Parathyroid hormone degradation by opossum kidney cells via receptor-mediated endocytosis and lysosomal hydrolysis

1992 ◽  
Vol 127 (3) ◽  
pp. 267-270 ◽  
Author(s):  
Toru Yamaguchi ◽  
Makoto Arao ◽  
Masaaki Fukase
Keyword(s):  
Parathyroid Hormone ◽  
Biologically Active ◽  
Main Role ◽  
Kidney Cells ◽  
Binding Studies ◽  
Opossum Kidney ◽  
Receptor Mediated Endocytosis ◽  
Opossum Kidney Cell ◽  
Opossum Kidney Cells

The mechanisms involved in parathyroid hormone (PTH) degradation by proximal renal tubule cells were studied using an opossum kidney cell line possessing PTH receptors as an in vitro model system. One hour incubation of 5 nmol/l human (h) PTH-(1-84) with intact opossum kidney cells (4.0× 106 cells) resulted in about 70% degradation and disappearance of hPTH-(1-84) from the medium, as determined by a two-site immunoradiometric assay. Preincubation with 100 nmol/l h[Nle8, Nle18, Tyr34]PTH-(1-34)amide for 6, 24, 48 and 72 h caused a 26, 47, 62 and 73% decrease, respectively, in PTH degradation by opossum kidney cells. Binding studies with 125I-labeled h[Nle8, Nle18, Tyr34]PTH-(1-34)amide as a radioligand showed that PTH receptor binding decreased with the time of pretreatment with the agonist. Pretreatments of the cells with monensin, an inhibitor of endocytosis, and the lysosomotropic agents such as chloroquine, ammonium chloride and leupeptin, inhibited degradation of hPTH-(1-84) by 87, 71, 76 and 72%, respectively. Concentrations of 5 nmol/l hPTH-(39-84) and hPTH-(39-68), which are known not to bind to PTH receptors appreciably, were not degraded by opossum kidney cells during 1 h incubations. Thus intact, biologically active PTH, but not its inactive fragments, is degraded by opossum kidney cells, by receptor-mediated endocytosis and lysosomal hydrolysis. A mechanism resembling the peritubular uptake of intact PTH by perfused kidneys reported previously appears to play a main role in PTH metabolism by cultured renal cells.

scholarly journals Long-term protein exposure reduces albumin binding and uptake in proximal tubule-derived opossum kidney cells.

1998 ◽  
Vol 9 (6) ◽  
pp. 960-968 ◽  
Author(s):  
M Gekle ◽  
S Mildenberger ◽  
R Freudinger ◽  
S Silbernagl
Keyword(s):  
Amino Acids ◽  
Proximal Tubule ◽  
Uptake Rate ◽  
Kidney Cells ◽  
Proximal Tubular Cells ◽  
Opossum Kidney ◽  
Tubular Cells ◽  
Opossum Kidney Cells ◽  
Proximal Tubular ◽  
Protein Reabsorption

To avoid renal loss of large amounts of proteins, filtered proteins are reabsorbed by endocytosis along the proximal tubule. However, although protein reabsorption is a task of proximal tubular cells, it is also a threat because it may cause cell injury. This study determines whether exposure to bovine serum albumin (BSA) leads to regulatory changes in endocytosis of FITC-BSA in proximal tubule-derived opossum kidney cells. Preincubation with BSA led to a decrease of FITC-BSA endocytosis with an IC50 value of 0.58 g/L. Specific binding of FITC-BSA to the apical membrane was also reduced (IC50 = 0.69 g/L). Kinetic analyses revealed that maximal uptake rate and maximal binding capacity were decreased with no change in affinity. Similar effects were observed after preincubation with equimolar amounts of other proteins (lactalbumin, transferrin, and conalbumin), but not after preincubation with dextran. The effect of preincubation with BSA could be mimicked by preincubation with some amino acids. Preincubation with L-Ala, L-Gln, or NH4Cl, but not with L-Leu, L-Glu, or L-Asp, reduced FITC-BSA endocytosis and binding. Preincubation with BSA, but not with dextran, reduced protein degradation and increased ammonia production, vesicular pH, as well as the rate of lactate dehydrogenase release. Apical fluid-phase endocytosis and apical uptake of neutral amino acids were not reduced. It is concluded that proximal tubular cells reduce the uptake rate for proteins, but not for other substrates, in response to increased protein load. This reduction is achieved by reducing the number of apical binding sites, partially in response to increased ammoniagenesis with deranged vesicular pH and enzyme activities. Thus, increased protein filtration could result in reduced protein reabsorption, thereby enhancing proteinuria.

scholarly journals The paracellular permeability of opossum kidney cells, a proximal tubule cell line

1999 ◽  
Vol 56 (6) ◽  
pp. 2304-2308 ◽  
Author(s):  
Mingyu Liang ◽  
Carla R. Ramsey ◽  
Franklyn G. Knox
Keyword(s):  
Proximal Tubule ◽  
Cell Line ◽  
Paracellular Permeability ◽  
Proximal Tubule Cell ◽  
Kidney Cells ◽  
Tubule Cell ◽  
Opossum Kidney ◽  
Opossum Kidney Cells

Receptor-mediated endocytosis of albumin in cultured opossum kidney cells: a model for proximal tubular protein reabsorption

1991 ◽  
Vol 418 (4) ◽  
pp. 383-392 ◽  
Author(s):  
Johann S. Schwegler ◽  
Bernd Heppelmann ◽  
Sigrid Mildenberger ◽  
Stefan Silbernagl
Keyword(s):  
Kidney Cells ◽  
Opossum Kidney ◽  
Receptor Mediated Endocytosis ◽  
Opossum Kidney Cells ◽  
Proximal Tubular ◽  
Protein Reabsorption

scholarly journals Citrate and succinate transport in proximal tubule cells

2000 ◽  
Vol 278 (3) ◽  
pp. F492-F498 ◽  
Author(s):  
Kathleen S. Hering-Smith ◽  
Cecilia T. Gambala ◽  
L. Lee Hamm
Keyword(s):  
Proximal Tubule ◽  
Apical Membrane ◽  
Low Ph ◽  
Extracellular Ph ◽  
Kidney Cells ◽  
Proximal Tubule Cells ◽  
Opossum Kidney ◽  
Opossum Kidney Cells ◽  
Tubule Cells ◽  
Urinary Citrate

Urinary citrate, which inhibits calcium nephrolithiasis, is determined by proximal reabsorption via an apical dicarboxylate transporter. Citrate is predominantly trivalent at physiological pH, but citrate− 2 is transported at the apical membrane. We now demonstrate that low-Ca solutions induce transport of citrate− 2 and succinate in opossum kidney cells. With 1.2 mM extracellular Ca, citrate uptake was pH insensitive and not competed by succinate− 2. In contrast, with low extracellular Ca, citrate uptake increased twofold, was inhibited by succinate (and other dicarboxylates), was stimulated by lowering extracellular pH (consistent with citrate− 2 transport), and increased further by lowering extracellular Mg. The effect of Ca was incrementally concentration dependent, between 0 and 1.2 mM. The effect of Ca was not simply complexation with citrate because succinate (which is complexed significantly less) was affected by Ca similarly. Incubation of cells for 48 h in a low-pH media increased citrate transport (studied at control pH) more than twofold, suggesting induction of transporters.

Resistance to parathyroid hormone-induced inhibition of inorganic phosphate transport in opossum kidney cells cultured in low inorganic phosphate medium

1992 ◽  
Vol 134 (3) ◽  
pp. 361-368 ◽  
Author(s):  
J. Caverzasio ◽  
J.-P. Bonjour
Keyword(s):  
Inorganic Phosphate ◽  
Kidney Cells ◽  
Camp Production ◽  
Cellular Resistance ◽  
Opossum Kidney ◽  
Pi Transport ◽  
Camp Generation ◽  
Opossum Kidney Cells ◽  
Cells Cultured ◽  
In Cells

ABSTRACT Renal resistance to the phosphaturic action of parathyroid hormone (PTH) is observed during dietary deprivation of inorganic phosphate (Pi) in vivo. In the present work, the influence of short (3 h)- or long (72 h)-term deprivation of Pi on the effect of bovine PTH (bPTH(1–34)) on both Na-dependent Pi transport and cyclic AMP(cAMP) production was examined in cultured opossum kidney epithelium. Na-dependent Pi transport increased by 100% in cells exposed to low Pi medium containing no Pi (LPM) for 3 h, as compared with transport in high Pi medium containing 2 mmolPi/l (HPM). In response to a submaximal dose (1 nmol/l) of bPTH(1–34), Na-dependent Pi transport was similarly inhibited by about 40% in LPM and HPM. This inhibition was preceded by increased cAMP production which was identical in LPM and HPM. In opossum kidney cells exposed for 72 h to LPM, Na-dependent Pi transport was also increased by 100% compared with that in HPM. However, bPTH(1–34) added at 1 nmol/l did not induce any significant change in Na-dependent Pi transport or cAMP. Stimulation of cAMP could only be elicited at bPTH(1–34) concentrations higher than 1 nmol/l. Such a reduced cAMP response was also observed with forskolin in cells incubated for 72 h in LPM. The cellular resistance to the generation of cAMP was associated with a significantly lower level of ATP in cells cultured for 72 h in LPM compared with ATP levels in HPM. There was a good relationship between cellular ATP level and expression of the inhibitory effect of bPTH on Pi transport in culture media containing various concentrations of Pi. In conclusion, long-term Pi depletion in opossum kidney cells leads to cellular resistance to PTH-induced cAMP generation and inhibition of Pi transport. The lower level of cAMP in Pi-depleted cells is probably due to insufficient substrate for cAMP generation. It is likely that other ATP-dependent processes involved in cellular Pi transport regulation might also be affected in the severely Pi-depleted cells and contribute to the resistance of PTH action on Pi transport inhibition. Journal of Endocrinology (1992) 134, 361–368

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