Phosphate transport by rat intestinal basolateral-membrane vesicles

Kikuchi, Kazuhiro; Arab, Noushin

doi:10.1042/bj2430641

Cited by 18 publications

(9 citation statements)

References 14 publications

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“…The results suggest that the defect in Hyp phenotype is not expressed in the BLMV of renal and jejunal epithelium. The presence of an Na+-dependent process for phosphate uptake is similar to our previous studies in humans ( 16) and rats ( 17).…”

Section: Discussionsupporting

confidence: 90%

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Transport of Phosphate by Plasma Membranes of the Jejunum and Kidney of the Mouse Model of Hypophosphatemic Vitamin D-Resistant Rickets

Nakagawa

1993

Experimental Biology and Medicine

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The hypophosphatemic mouse is a useful model for the study of hypophosphatemic vitamin D-resistant rickets in humans. Hypophosphatemia and hyperphosphaturia are the main biochemical findings in the patients and in mice with the disorder. The exact membrane localization of the site of the defect in phosphate transport in humans is not known. We utilized a well-validated technique of brush border and basolateral membrane vesicles to investigate phosphate transport across the enterocyte and the renal tubule cells of the hypophosphatemic (Hyp) mice model. Phosphate uptake by brush border membranes of jejunal enterocytes revealed similar initial rates (slopes were 0.007 and 0.006 for Hyp and control mice, respectively). Kinetics of jejunal Na(+)-dependent phosphate uptake showed a Vmax of 0.21 +/- 0.03 and 0.19 +/- 0.02 nmol/mg protein/15 sec, and Km of 0.12 +/- 0.07 and 0.09 +/- 0.02 mM in the Hyp and control mice, respectively. Kinetics of basolateral uptake of phosphate were also similar (Vmax of 0.05 +/- 0.01 and 0.06 +/- 0.02 nmol/mg protein/10 sec and Km of 0.013 +/- 0.004 and 0.028 +/- 0.022 mM, respectively). On the other hand, kinetics of Na(+)-dependent phosphate uptake by renal brush border membrane vesicles (BBMV) were markedly decreased (Vmax of 0.42 +/- 0.03 and 1.09 +/- 0.06 nmol/mg protein/15 sec, P < 0.01, and Km of 0.01 +/- 0.003 and 0.05 +/- 0.02 mM, P < 0.02, in the Hyp and control mice, respectively). Kinetics of Na(+)-dependent phosphate uptake by renal basolateral membrane were not decreased (Vmax of 0.19 +/- 0.02 and 0.21 +/- 0.02 nmol/mg protein/10 sec and Km of 0.012 +/- 0.003 and 0.012 +/- 0.004 mM for Hyp and control mice, respectively). To determine whether the decrease in renal BBMV is secondary to alteration in the Na(+)-dependent phosphate transporter or due to changes in the Na+ gradient, two studies were conducted: first, a tracer exchange study in renal BBMV which showed a decrease in phosphate uptake in Hyp BBMV compared with controls, confirming the kinetic studies; and second, an Na+ permeability study in renal BBMV of Hyp and control mice which showed no differences in Na+ permeability across the renal BBMV. These findings suggest that the defect in the hypophosphatemic mice is localized only to the brush border membranes of the kidney and is not due to alteration in the driving forces across the membranes.

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Section: Discussionsupporting

confidence: 90%

“…Previously, we have shown that jejunal basolateral membranes prepared with Percoll density gradient lack Na+ gradient-dependent glucose uptake and possess an ATP-dependent calcium uptake ( 16,17). To provide functional evidence for the renal basolateral membranes in the Hyp and control mice, we carried out two experiments.…”

Section: Resultsmentioning

confidence: 99%

Transport of Phosphate by Plasma Membranes of the Jejunum and Kidney of the Mouse Model of Hypophosphatemic Vitamin D-Resistant Rickets

Nakagawa

1993

Experimental Biology and Medicine

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“…Functional studies on rat jejunum suggest that basolateral P i transport involves a Na-independent carrier-mediated mechanism, which is driven by the electrochemical gradient, and/or the presence of high-affinity Na-dependent P i carriers (Danisi et al, 1984;Quamme, 1985). In contrast, the study of Ghishan et al (1987) revealed Na-dependent transport systems that have also been postulated for human small intestine . Nevertheless, the rate limiting step of entire transepithelial Pi transport in porcine small intestine appears to be apical P i uptake and therefore basic research on the mechanisms and regulation of the transporter's capacity and specificity is essential.…”

Section: Phosphate Absorptionmentioning

confidence: 96%

Transport of nutrients and electrolytes across the intestinal wall in pigs

Breves¹,

Kock²,

Schröder³

2007

Livestock Science

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“…Uptake of phosphate was measured by a rapid filtration technique (13) as used previously in our laboratory (6)(7)(8). Briefly, vesicles obtained in the 100,000 x g centrifugation were preincubated in a solution containing 120 mM KCl, 5 mM MgC12, and 10 mM Hepes/Tris buffer, pH 7.2.…”

Section: Methodsmentioning

confidence: 99%

“…Jejunal phosphate transport take place against an electrochemical gradient and is inhibited by arsenate (1)(2)(3)(4)(5)(6)(7)(8). The uptake of phosphate at the brush border membrane consists of two components: a saturable, electroneutral sodium dependent component and an unsaturable, sodium-independent component (1, 2).…”

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confidence: 99%

Phosphate Transport hy Intestinal Endoplasmic Reticulum during Maturation

Arab

1988

Pediatr Res

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ABSTRAm. The transport of phosphate into jejunal endoplasmic reticulum vesicles isolated from suckling and adolescent rats was investigated using a rapid filtration technique. Intestinal endoplasmic reticulum from both ages were enriched with NADPH cytochrome-C-reductase whereas other markers for brush border, basolateral, mitochondrial, and Golgi apparatus were impoverished. Phosphate uptake represented an energy-dependent process as evident by more than 80% decrease in uptake values at 0" C compared to 25" C. Phosphate uptake was ATP dependent in both age groups, however, mean uptake values were significantly greater in suckling rats compared to adolescent rats. pH optimum for uptake was 7.2. p-Chloromercuribenzoate at 100 pM concentration inhibited phosphate uptake by more than 90%. Initial rate of phosphate uptake was linear up to 45 s. Kinetics of phosphate uptake at 30 s showed a K, of 0.7 + 0.1 and 0.15 2 0.1 suckling and adolescent rats, respectively. V,., was 1.5 + 0.5 and 0.14 f 0.01 nmol/mg protein/30 s for both suckling and adolescent rats, respectively. Herein we provide evidence for the first time for the presence of a phosphate carrier in intestinal endoplasmic reticulum of rats. Endoplasmic reticulum of phosphate uptake was significantly greater in suckling rats compared to adolescent rats. This increase in uptake is due to a greater number and activity of phosphate carriers in suckling rats. (Pediatr Res 23: 612-615, 1988)The transport of phosphate across the small intestine of suckling and adult animals occurs by an active process (1-5). Jejunal phosphate transport take place against an electrochemical gradient and is inhibited by arsenate (1-8). The uptake of phosphate at the brush border membrane consists of two components: a saturable, electroneutral sodium dependent component and an unsaturable, sodium-independent component (1, 2). The energy driving the sodium-dependent entry of phosphate into the cell is provided by an extracellular to intracellular Na+ gradient maintained by the Na+-K+-ATPase at the basolateral membrane (5). Both sodium-dependent and -independent brush border phosphate uptake are higher in suckling rats compared to adult rats (6). Phosphate exit at the basolateral membrane of the enterocyte occurs by a camer-mediated process that is sodium dependent, electroneutral with stoichiometry of 2 Na:l phosphate at pH 7.4 (7). The transcellular movement of phosphate is unknown. Recently, we described an important role for the endoplasmic reticulum in transcellular calcium transport (8). This process is ATP dependent and exhibits characteristic devel- opmental patterns (8). Our study was designed to investigate the role of intestinal endoplasmic reticulum in phosphate transport during maturation in the rat. We used a millipore filtration system to study phosphate uptake by intestinal microsomes. EXPERIMENTAL PROCEDURES Isolation of intestinal endoplasmic reticulum vesicles.The jejunum of two adolescent rats (42 + 2 days) of 12 suckling rats (14 + 1 day) were used to prepare the en...

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Phosphate transport by rat intestinal basolateral-membrane vesicles

Cited by 18 publications

References 14 publications

Transport of Phosphate by Plasma Membranes of the Jejunum and Kidney of the Mouse Model of Hypophosphatemic Vitamin D-Resistant Rickets

Transport of Phosphate by Plasma Membranes of the Jejunum and Kidney of the Mouse Model of Hypophosphatemic Vitamin D-Resistant Rickets

Transport of nutrients and electrolytes across the intestinal wall in pigs

Phosphate Transport hy Intestinal Endoplasmic Reticulum during Maturation

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