Thyroid hormone stimulation of Na/Pi-cotransport in opossum kidney cells.
Thyroid hormone (T3), a known stimulator of renal proximal tubular brush border membrane Na-dependent phosphate (Pi) uptake (Na/Pi-cotransport), stimulated Na-dependent Pi transport in opossum kidney (OK) cells. Na/Pi-cotransport was stimulated in a time- and dose-dependent manner with maximal effects (57%) at 24 h and 10(-10) M T3. This stimulation was related to an increase in the apparent capacity (Vmax) of Na/Pi-cotransport. Treatment with T3 had no effect on Na-independent transport of Pi or of L-arginine. The stimulation of Na/Pi-cotransport was paralleled by an increase in the messenger ribonucleic acid (mRNA) encoding the OK cell apical Na/Pi-cotransporter (termed NaPi-4); the mRNA levels related to the activity of Na-independent L-arginine transport (rBAT) were unaffected by T3. Actinomycin D (10(-7) M) completely prevented the stimulatory effect of T3 on OK cell Na/Pi-cotransport and on NaPi-4 mRNA content. In conclusion, T3 stimulates apical Na/Pi-cotransport in OK cells most likely by enhancing its transcription.
Sorribas
V
V
Institute of Physiology, University of Zürich, Switzerland.
Markovich
D
D
Verri
T
T
Biber
J
J
Murer
H
H
D000818:Animals; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000096:biosynthesis / Q000378:metabolism*; D002478:Cells, Cultured; D003609:Dactinomycin / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D009893:Opossums / Q000378:metabolism*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D050608:Sodium-Phosphate Cotransporter Proteins; D027981:Symporters; D013963:Thyroid Hormones / Q000494:pharmacology*; D014284:Triiodothyronine / Q000494:pharmacology
D002352:Carrier Proteins; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D050608:Sodium-Phosphate Cotransporter Proteins; D027981:Symporters; D013963:Thyroid Hormones; D014284:Triiodothyronine; D003609:Dactinomycin; D004815:Epidermal Growth Factor