Parathyroid hormone inhibits plasma membrane Pi transport without changing endocytic activity in opossum kidney cells

Michelle S. Paraiso, James A. McAteer, Stephen A. Kempson

Research output: Contribution to journalArticle

4 Scopus citations


Parathyroid hormone (PTH) inhibits Na+-dependent Pi uptake in renal epithelial cells from opossum kidney (OK). This requires an intact endocytic pathway, suggesting that one action of PTH may be to promote endocytic removal of Na+/Pi cotransporters from the cell membrane. The present study tested if PTH, at a dose that inhibited membrane Pi transport, also produced an increase in endocytic activity. Pi transport was measured in isolated plasma membrane vesicles. Endocytosis was measured by allowing cells to take up horseradish peroxidase (HRP) followed by assay of triton-sensitive (latent) HRP activity in subcellular fractions isolated by density gradient centrifugation. Incubation of OK cells with 10-7 M PTH for 3 h decreased Na+/Pi cotransport by membrane vesicles to 328 ± 54 pmol/mg/min compared to 448 ± 67 pmol/mg/min (mean ± S.E., P < 0.03) in controls. Latent HRP content of endosomal fractions was dependent on the time and temperature used to load cells with HRP and on the concentration of HRP. However, incubation of OK cells with 10-7 M PTH for either 1 or 3 h produced no change in latent HRP activity. Thus the action of PTH on the Na+/Pi cotransporter in the plasma membrane of OK cells does not require a change in the rate of endocytosis.

Original languageEnglish (US)
Pages (from-to)143-147
Number of pages5
JournalBiochimica et Biophysica Acta - Molecular Cell Research
Issue number2
StatePublished - Jan 1 1995



  • Endocytosis
  • Kidney cell
  • Membrane vesicle
  • Parathyroid hormone
  • Phosphate transport

ASJC Scopus subject areas

  • Biophysics
  • Cell Biology
  • Molecular Biology

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