Normal phosphate transport in cells from the S2 and S3 segments of Hyp-mouse proximal renal tubules

Endocrinology
T NesbittM K Drezner

Abstract

An intrinsic phosphate (Pi) transport defect in the proximal tubule (PT) presumably underlies X-linked hypophosphatemic rickets. We recently reported normal Pi transport in the S1 segment of the Hyp mouse PT. Whether Pi wasting results from an abnormality in the S2 or S3 segment remains unknown. Thus, we compared Pi transport in S2 and S3 immortalized cells from transgenic (simian virus 40) normal and Hyp mice. These cells display biochemical features of PT cells, including alkaline phosphatase- and hormone- stimulated cAMP activity as well as gluconeogenesis. Moreover, kinetic studies in S2 cells reveal a similar Km[0.26 +/- 0.03 (+/-SEM) vs. 0.22 +/- 0.03 mM] and maximum velocity (Vmax; 5.5 +/- 0.66 vs. 5.9 +/- 0.72 nmol/mg x 5 min) in normal and Hyp mice, respectively. Km and Vmax were also similar in cells from the S3 segment; however, the Vmax values in S3 cells in normal and Hyp mice (2.8 +/- 0.45 and 3.0 +/- 0.56 nmol/mg x 5 min) were reduced in both animal models compared to those in S2 cells (P < 0.001), whereas the Km values in S3 cells from normal and Hyp mice (0.10 +/- 0.02 and 0.11 +/- 0.04 mM) were increased relative to those in S2 cells (P < 0.001). These data indicate that Pi transport throughout the PT of Hyp m...Continue Reading

Citations

Mar 27, 2013·Proceedings of the National Academy of Sciences of the United States of America·Zachary C RyanRajiv Kumar
Sep 4, 2003·Proceedings of the National Academy of Sciences of the United States of America·Michel BaumRaymond Quigley
Feb 1, 1997·The Journal of General Physiology·K E WhiteP A Friedman
Feb 22, 2012·Critical Reviews in Eukaryotic Gene Expression·Peter S N Rowe
Mar 28, 2009·American Journal of Kidney Diseases : the Official Journal of the National Kidney Foundation·Olivera Marsenic
Sep 30, 2004·American Journal of Physiology. Renal Physiology·Michel BaumRaymond Quigley
May 25, 2006·Pediatric Nephrology : Journal of the International Pediatric Nephrology Association·Michel BaumMouin Seikaly
Aug 5, 1998·Current Opinion in Nephrology and Hypertension·P S Rowe
Jan 5, 2000·Kidney International·M K Drezner

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