Functional asymmetry in phosphate transport and its regulation in opossum kidney cells: parathyroid hormone inhibition

1990 ◽  
Vol 416 (6) ◽  
pp. 624-631 ◽  
Author(s):  
Stephan J. Reshkin ◽  
Judith Forgo ◽  
Heini Murer
Keyword(s):  
Parathyroid Hormone ◽  
Phosphate Transport ◽  
Functional Asymmetry ◽  
Kidney Cells ◽  
Opossum Kidney ◽  
Opossum Kidney Cells

Regulation of Na+/H+ exchange in opossum kidney cells by parathyroid hormone, cyclic AMP and phorbol esters

1990 ◽  
Vol 415 (4) ◽  
pp. 461-470 ◽  
Author(s):  
Corinna Helmle-Kolb ◽  
Marshall H. Montrose ◽  
Gerti Stange ◽  
Heini Murer
Keyword(s):  
Parathyroid Hormone ◽  
Cyclic Amp ◽  
Phorbol Esters ◽  
Kidney Cells ◽  
Opossum Kidney ◽  
Opossum Kidney 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.

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