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Phosphophloretin sensitivity of rabbit renal NaPi-IIa and NaPi-Ia

Department of Physiology and Biophysics, University of Texas Medical Branch, Galveston, Texas 77555-0641

Submitted 15 July 2003 ; accepted in final form 26 December 2003

The effect of phosphorylated phloretins on Na⁺-dependent phosphate uptake into rabbit renal brush-border membrane vesicles (BBMV) was examined. Na⁺-dependent phosphate uptake into isolated rabbit cortex BBMV was sensitive to 2'-phosphophloretin (2'-PP) and 2'-phospho-4',4,6'-trimethoxy phloretin (PTMP) in a dose-dependent and pH-dependent manner. PTMP inhibition of Na⁺-dependent phosphate uptake was maximum at alkali pH, and 2'-PP inhibition of Na⁺-dependent phosphate uptake was maximum at acidic pH. Increasing Na⁺ concentrations did not increase PTMP inhibition of renal cortex BBMV Na⁺-dependent phosphate uptake at pH 6. The effect of phosphophloretins on Na⁺-dependent phosphate uptake was examined in BBMV isolated from purified proximal tubules and distal tubules. 2'-PP and PTMP inhibition of Na⁺-dependent phosphate uptake into BBMV isolated from purified proximal tubules was similar to the inhibition seen with BBMV from renal cortex. 2'-PP, but not PTMP, inhibited Na⁺-dependent phosphate uptake into BBMV isolated from purified distal tubules. The pH dependence of inhibition, the absence of PTMP inhibition of Na⁺-dependent phosphate uptake into distal tubule BBMV, and the inhibition of Na⁺-dependent phosphate uptake into distal tubule BBMV suggest that NaPi-Ia is 2'-PP sensitive and NaPi-IIa is PTMP sensitive.

intestinal brush-border membrane vesicles; renal brush-border membrane vesicles; sodium-phosphate cotransport; phosphate reabsorption; 2'-phosphophloretin; 2'-phospho-4',4,6'-trimethoxy phloretin

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				B. E. Peerce, L. Weaver, and R. D. Clarke Effect of 2'-phosphophloretin on renal function in chronic renal failure rats Am J Physiol Renal Physiol, July 1, 2004; 287(1): F48 - F56. [Abstract] [Full Text] [PDF]