PMID: 3099845Feb 12, 1987

Effect of pH on the kinetics of Na+-dependent phosphate transport in rat renal brush-border membranes

Biochimica Et Biophysica Acta
R J BindelsC H van Os

Abstract

The kinetics of Na+-dependent phosphate uptake in rat renal brush-border membrane vesicles were studied under zero-trans conditions at 37 degrees C and the effect of pH on the kinetic parameters was determined. When the pH was lowered it turned out to be increasingly difficult to estimate initial rates of phosphate uptake due to an increase in aspecific binding of phosphate to the brush border membrane. When EDTA or beta-glycerophosphate was added to the uptake medium this aspecific binding was markedly reduced. At pH 6.8, initial rates of phosphate uptake were measured between 0.01 and 3.0 mM phosphate in the presence of 100 mM Na+. Kinetic analysis resulted in a non-linear Eadie-Hofstee plot, compatible with two modes of transport: one major low-affinity system (Km approximately equal to 1.3 mM), high-capacity system (Vmax approximately equal to 1.1 nmol/s per mg protein) and one minor high-affinity (Km approximately equal to 0.03 mM), low-capacity system (Vmax approximately equal to 0.04 nmol/s per mg protein). Na+-dependent phosphate uptake studied far from initial rate conditions i.e. at 15 s, frequently observed in the literature, led to a dramatic decrease in the Vmax of the low-affinity system. When both the extra- and ...Continue Reading

References

Jul 1, 1973·Journal of Theoretical Biology·G W Borst-Pauwels
Dec 12, 1980·Biochimica Et Biophysica Acta·M R HammermanK A Hruska

Citations

Jul 1, 1988·In Vitro Cellular & Developmental Biology : Journal of the Tissue Culture Association·C L BellC R Scriver
Aug 16, 1994·Proceedings of the National Academy of Sciences of the United States of America·A E BuschF Lang
Apr 19, 2012·Drug Metabolism and Pharmacokinetics·Moto KajiwaraKen-ichi Inui
Jan 6, 2010·Drug Metabolism and Disposition : the Biological Fate of Chemicals·Tomoya YasujimaHiroaki Yuasa
Jan 25, 2006·Experimental Physiology·Joanne MarksEdward S Debnam
Apr 8, 1998·The American Journal of Physiology·R T Timmer, R B Gunn
Sep 1, 1995·Pflügers Archiv : European journal of physiology·C M HartmannH Murer
Dec 5, 2018·Pflügers Archiv : European journal of physiology·Laurent Beck
Apr 13, 1999·The American Journal of Physiology·I C ForsterS Eskandari
May 1, 1991·The American Journal of Physiology·H MurerJ Biber

Related Concepts

beta-glycerophosphoric acid, calcium salt (1: 1)
Edetic Acid, Sodium Salt
Calcium Glycerophosphate
Hydrogen-Ion Concentration
Kidney Tubules, Proximal
Microvilli
Orthophosphate
Rats, Inbred WKY
Sodium

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