Renal adaptation to dietary phosphate deprivation: role of proximal tubule brush-border membrane fluidity.
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)
Levine
B S
BS
Department of Medicine, School of Medicine, University of California, Los Angeles.
Knibloe
K A
KA
Golchini
K
K
Hashimoto
S
S
Kurtz
I
I
D000222:Adaptation, Physiological; D000777:Anesthetics / Q000494:pharmacology; D000818:Animals; D004032:Diet; D004161:Diphenylhexatriene / Q000737:chemistry / Q000378:metabolism; D007668:Kidney / Q000502:physiology*; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008297:Male; D008560:Membrane Fluidity; D008871:Microvilli / Q000378:metabolism; D010710:Phosphates / Q000172:deficiency*; D011392:Proline / Q000493:pharmacokinetics; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000494:pharmacology
D000777:Anesthetics; D010710:Phosphates; D004161:Diphenylhexatriene; D011392:Proline; D012964:Sodium