| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
1 Department of Physiology and Biophysics, Georgetown University School of Medicine, Washington, District of Columbia 20007 and 2 Department of Internal Medicine, University of Texas Southwestern Medical Center and Department of Veterans Affairs Medical Center, Dallas, Texas 75216
To determine the tubular sites and mechanisms involved in enhanced renal phosphate (Pi) reabsorption seen in the juvenile animal, renal micropuncture experiments were performed in acutely thyroparathyroidectomized adult (>14 wk old) and juvenile (4 wk old) male Wistar rats fed either a normal Pi diet (NPD, 0.6% Pi) or low Pi diet (0.07% Pi) for 2 days, in the presence and absence of parathyroid hormone (PTH). Pi reabsorption was greater in proximal convoluted (PCT) and straight tubules (PST) of the juvenile compared with adult rats fed NPD, whether or not PTH was present. These findings were consistent with a greater Pi uptake in brush-border membrane (BBM) vesicles from both superficial (SC) and outer juxtamedullary (JMC) cortices of juvenile animals. Western blot analysis revealed a 2- and 1.8-fold higher amount of NaPi-2 protein in the SC and JMC, respectively, in juvenile rats. Immunofluorescence microscopy also indicated that NaPi-2 protein expression was present in the proximal tubule (PT) BBM to a greater extent in juvenile rats. Dietary Pi restriction in juvenile rats resulted in a significant increase in Pi reabsorption in the PCT and PST segments. NaPi-2 expression in the PT BBM was also increased, as was the expression of intracellular NaPi-2 protein. These studies indicate that Pi reabsorption in both the PCT and PST segments of the renal tubule contributes to the attenuated response to PTH in the normal juvenile animal. In addition, dietary Pi restriction in the juvenile rat upregulates BBM NaPi-2 expression, which is associated with a further increase in proximal tubular Pi reabsorption.
kidney; low dietary phosphate; parathyroid hormone; age; brush-border membrane; inorganic phosphate transport
This article has been cited by other articles:
|
|
 |
|
  J. L. Rogers, A. R. Mitchell, C. Maric, K. Sandberg, A. Myers, and S. E. Mulroney Effect of sex hormones on renal estrogen and angiotensin type 1 receptors in female and male rats Am J Physiol Regulatory Integrative Comp Physiol, February 1, 2007; 292(2): R794 - R799. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. E. Mulroney, C. B. Woda, N. Halaihel, B. Louie, K. McDonnell, J. Schulkin, A. Haramati, and M. Levi Central control of renal sodium-phosphate (NaPi-2) transporters Am J Physiol Renal Physiol, April 1, 2004; 286(4): F647 - F652. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. H. Sugiura, N. K. McDaniel, and R. P. Ferraris In vivo fractional Pi absorption and NaPi-II mRNA expression in rainbow trout are upregulated by dietary P restriction Am J Physiol Regulatory Integrative Comp Physiol, October 1, 2003; 285(4): R770 - R781. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Y. Xu, C.-H. Yeung, I. Setiawan, C. Avram, J. Biber, A. Wagenfeld, F. Lang, and T. G. Cooper Sodium-Inorganic Phosphate Cotransporter NaPi-IIb in the Epididymis and Its Potential Role in Male Fertility Studied in a Transgenic Mouse Model Biol Reprod, October 1, 2003; 69(4): 1135 - 1141. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |
