Low phosphate diet upregulates the renal and intestinal sodium-dependent phosphate transporter in vitamin D-resistant hypophosphatemic mice

N. Nakagawa, Fayez K Ghishan

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Abstract

Renal and jejunal absorption of inorganic phosphate (P(i)) increases with dietary P(i) restriction in the rat. The defect in Na+-dependent phosphate transporter has been localized to the kidney of the Hyp mice; however, the adaptation to low-P(i) diet in both kidney and jejunum of the Hyp mice has not been well characterized. Therefore, the current studies were designed to characterize the adaptation of renal and jejunal Na+-dependent phosphate transport in the Hyp mice and compare it with normal mice. Low-P(i) diet significantly increased the slope of the initial rate of renal brush border membrane (BBM) phosphate uptake compared with corresponding values in mice raised on control-P(i) diet (0.035 vs 0.017) (P < 0.01). Kinetics of renal Na+-dependent phosphate uptake in Hyp mice showed a V(max) of 1.00 ± 0.01 and 0.46 ± 0.02 nmoles/mg protein/15 sec in low- and control-P(i) diets, respectively (P < 0.01), whereas, K(m) values were 0.07 ± 0.04 and 0.02 ± 0.01, respectively. Similar kinetic analysis in renal BBM of normal mice showed a V(max) of 2.4 ± 0.17 and 1.18 ± 0.09 (P < 0.01) and K(m) of 0.07 ± 0.03 and 0.08 ± 0.03 on low and control P(i) diets, respectively. Similarly, low-P(i) diet significantly increased the slope of the initial rate of intestinal phosphate uptake (0.013 and 0.007) (P < 0.01). Kinetics of jejunal Na+-dependent phosphate uptake in Hyp mice showed a V(max) of 0.36 ± 0.01 and 0.2 ± 0.02 nmoles/mg protein/15 sec, (P < 0.01) and K(m) of 0.13 ± 0.06 and 0.06 ± 0.01 mM in low- and in control-P(i) diet, respectively. Kinetic analysis in jejunal BBM of normal mice showed a V(max) of 0.47 ± 0.04 and 0.18 ± 0.01 nmoles/mg protein/15 sec (P < 0.01) and K(m) of 0.16 ± 0.04 and 0.11 ± 0.01 in low- and control-P(i) diets, respectively. The data indicates that low-phosphate diet upregulates the V(max) of the renal and jejunal Na+-dependent phosphate cotransporter in the hypophosphatemic mice.

Original languageEnglish (US)
Pages (from-to)162-167
Number of pages6
JournalProceedings of the Society for Experimental Biology and Medicine
Volume205
Issue number2
Publication statusPublished - 1994
Externally publishedYes

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ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)

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