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

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• 作者：Paraiso ; Michelle S. ; McAteer ; James A. ; Kempson ; Stephen A.
• 关键词：Endocytosis ; Phosphate transport ; Kidney cell ; Parathyroid hormone ; Membrane vesicle
• 刊名：Biochimica et Biophysica Acta (BBA)/Molecular Cell Research
• 出版年：1995
• 出版时间：April 28, 1995
• 年：1995
• 卷：1266
• 期：2
• 页码：143-147
• 全文大小：468 K

文摘

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 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 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 cotransporter in the plasma membrane of OK cells does not require a change in the rate of endocytosis.