AJP - Renal Physiology, Vol 260, Issue 5 613-F618, Copyright © 1991 by American Physiological Society

ARTICLES

Renal adaptation to dietary phosphate deprivation: role of proximal tubule brush-border membrane fluidity

B. S. Levine, K. A. Knibloe, K. Golchini, S. Hashimoto and I. Kurtz
Department of Medicine, School of Medicine, University of California, Los Angeles.

With dietary phosphate (Pi) restriction, fluidity of renal proximal tubule brush-border membranes (BBM) and Na-dependent Pi transport (Na-Pi) are increased, suggesting that changes in BBM fluidity are critical for adaptation to Pi restriction. To test this hypothesis, the temporal relationship between Na-Pi transport and changes in BBM fluidity was assessed after Pi deprivation in rats. Renal cortex was obtained from rats fed either a 0.03% (-P) or a 0.6% (+P) Pi diet for 4 h or 7 days, and BBM were prepared. Na-Pi uptake by BBM was measured by use of rapid filtration, and BBM fluidity was assessed by use of the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene (DPH). After 4 h on the diets, Na-Pi uptake was 439 +/- 142 (SD) and 984 +/- 184 pmol.mg protein-1.5 s-1 in +P and -P, respectively (P less than 0.01, n, = 8). Na-dependent proline uptake was unchanged. DPH anisotropy and total cholesterol were similar between groups: 0.204 +/- 0.025 and 0.401 +/- 0.047 nmol/mg protein, respectively, in +P and 0.205 +/- 0.015 and 0.392 +/- 0.037 in -P (P greater than 0.05, n = 8-10). After 7 days, Na-Pi uptake was 841 +/- 291 in +P and 2,168 +/- 848 pmol.mg protein-1.5 s-1 in -P, P less than 0.01, n = 8. DPH anisotropy and BBM cholesterol were 0.175 +/- 0.019 and 443 +/- 132 nmol/mg protein, respectively, in +P and 0.162 +/- 0.020 (n = 8) and 341 +/- 128 (n = 3) in -P (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

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