Na+-Phosphate Cotransport in Mouse Distal Convoluted Tubule Cells: Evidence for Glvr-1 and Ram-1 Gene Expression

Autor: Harriet S. Tenenhouse, P. A. Friedman, Josée Martel, Bonita Coutermarsh, F. A. Gesek, Claude Gauthier
Rok vydání: 1998
Předmět:
medicine.medical_specialty
Virus genetics
Endocrinology
Diabetes and Metabolism
Gene Expression
Parathyroid hormone
Nephron
Biology
Binding
Competitive
Polymerase Chain Reaction
Kidney Tubules
Proximal
Mice
chemistry.chemical_compound
Internal medicine
medicine
Animals
Phosphate Transport Proteins
Orthopedics and Sports Medicine
Distal convoluted tubule
Kidney Tubules
Distal
Cells
Cultured
Forskolin
Symporters
Sodium-Phosphate Cotransporter Proteins
Type III
urogenital system
Reabsorption
Colforsin
Sodium-Phosphate Cotransporter Proteins
Hydrogen-Ion Concentration
Oligonucleotides
Antisense
Molecular biology
medicine.anatomical_structure
Endocrinology
chemistry
Parathyroid Hormone
Symporter
RNA
Receptors
Virus
Tetradecanoylphorbol Acetate
Carrier Proteins
Cotransporter
Sodium-Phosphate Cotransporter Proteins
Type I
Zdroj: Journal of Bone and Mineral Research. 13:590-597
ISSN: 0884-0431
Popis: While there is considerable evidence for phosphate (Pi) reabsorption in the distal tubule, Pi transport and its regulation have not been well characterized in this segment of the nephron. In the present study, we examined Na+-dependent Pi transport in immortalized mouse distal convoluted tubule (MDCT) cells. Pi uptake by MDCT cells is Na+-dependent and, under initial rate conditions, is inhibited by phosphonoformic acid (41 +/- 3% of control), a competitive inhibitor of Na+-Pi cotransport. The transport system has a high affinity for Pi (Km = 0.46 mM) and is stimulated by lowering the extracellular pH from 7.4 to 6.4 and inhibited by raising the pH from 7.4 to 8.4. Exposure to Pi-free medium for 21 h increased Na+-Pi cotransport from 2.1 to 5.5 nmol/mg of protein/5 minutes (p < 0.05) while parathyroid hormone, forskolin, and phorbol 12-myristate 13-acetate failed to alter Pi uptake in MDCT cells. Reverse transcriptase polymerase chain reaction of MDCT cell RNA provided evidence for the expression of the Npt1 but not the Npt2 Na+-Pi cotransporter gene. However, preincubation of MDCT cells with Npt1 antisense oligonucleotide led to only 20% inhibition of Na+-Pi cotransport, suggesting that other Na+-Pi cotransporters are operative in MDCT cells. Indeed, we showed, by ribonuclease protection assay, that MDCT cells express the ubiquitous cell surface receptors for gibbon ape leukemia virus (Glvr-1) and amphoteric murine retrovirus (Ram-1) that also function as Na+-Pi cotransporters. In summary, we demonstrate that the pH dependence and regulation of Na+-Pi cotransport in MDCT cells is distinct from that in the proximal tubule and suggest that different gene products mediate Na+-Pi cotransport in the proximal and distal segments of the nephron.
Databáze: OpenAIRE
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