Phosphate uptake by renal membrane vesicles of rabbits adapted to high and low phosphorus diets

1983 ◽  
Vol 245 (2) ◽  
pp. F175-F180 ◽  
Author(s):  
L. Cheng ◽  
C. T. Liang ◽  
B. Sacktor
Keyword(s):  
Transport System ◽  
Phosphate Uptake ◽  
Membrane Vesicles ◽  
Phosphate Transport ◽  
Uptake System ◽  
Low Phosphorus ◽  
Dietary Phosphate ◽  
Preferred Species ◽  
Uptake Medium ◽  
Phosphate Carrier

Renal adaptation to changes in phosphate intake was studied by comparing phosphate uptake by proximal tubule brush border membrane vesicles from rabbits on a relatively high or low phosphorus diet. The low phosphorus diet increased Na+ gradient-dependent phosphate uptake. Uptake in the absence of Na+ and in the presence of Na+, but no gradient, was not significantly affected. The phosphorus diet did not alter Na+ gradient-dependent D-glucose and L-proline uptake. The low phosphorus diet increased Vmax; affinity for phosphate was not appreciably changed. At all concentrations of extravesicular Na+, phosphate uptake was higher in membrane vesicles from animals fed the low phosphorus diet; the kinetics of the phosphate uptake system, with respect to Na+, was also altered by the change in dietary phosphate. These findings suggest that adaptation involves an alteration in the rate of translocation of the Na+-phosphate carrier when energized by a Na+ gradient driving force rather than a change in the number of Na+-phosphate carrier sites. With membrane vesicles from rabbits fed a low phosphorus diet, phosphate uptake increased several-fold when the pH of the uptake medium was raised, whereas with membrane vesicles from animals fed a high phosphorus diet the enhancement of uptake with alkalinization was relatively small. Irrespective of the diet, divalent phosphate was the probable preferred species for transport. Dietary adaptation was associated, however, with an alteration in the pH dependency of the transport system per se. These findings provide evidence that the adaptation of the kidney phosphate transport system to dietary phosphate load involves an intrinsic change in the Na+-phosphate carrier.

scholarly journals pH gradient as an additional driving force in the renal re-absorption of phosphate

1990 ◽  
Vol 271 (3) ◽  
pp. 687-692 ◽  
Author(s):  
J Strévey ◽  
S Giroux ◽  
R Béliveau
Keyword(s):  
Driving Force ◽  
Phosphate Uptake ◽  
Rat Kidney ◽  
Membrane Vesicles ◽  
Phosphate Transport ◽  
Kidney Cortex ◽  
Rat Kidney Cortex ◽  
Total Phosphate Concentration ◽  
Combined Action ◽  
Phosphate Carrier

The effects of the Na+ gradient and pH on phosphate uptake were studied in brush-border membrane vesicles isolated from rat kidney cortex. The initial rates of Na(+)-dependent phosphate uptake were measured at pH 6.5, 7.5 and 8.5 in the presence of sodium gluconate. At a constant total phosphate concentration, the transport values at pH 7.5 and 8.5 were similar, but at pH 6.5 the influx was 31% of that at pH 7.5. However, when the concentration of bivalent phosphate was kept constant at all three pH values, the effect of pH was less pronounced; at pH 6.5, phosphate influx was 73% of that measured at pH 7.5. The Na(+)-dependent phosphate uptake was also influenced by a transmembrane pH difference; an outwardly directed H+ gradient stimulated the uptake by 48%, whereas an inwardly directed H+ gradient inhibited the uptake by 15%. Phosphate on the trans (intravesicular) side stimulated the Na(+)-gradient-dependent phosphate transport by 59%, 93% and 49%, and the Na(+)-gradient-independent phosphate transport by 240%, 280% and 244%, at pH 6.5, 7.5 and 8.5 respectively. However, in both cases, at pH 6.5 the maximal stimulation was seen only when the concentration of bivalent trans phosphate was the same as at pH 7.5. In the absence of a Na+ gradient, but in the presence of Na+, an outwardly directed H+ gradient provided the driving force for the transient hyperaccumulation of phosphate. The rate of uptake was dependent on the magnitude of the H+ gradient. These results indicate that: (1) the bivalent form of phosphate is the form of phosphate recognized by the carrier on both sides of the membrane; (2) protons are both activators and allosteric modulators of the phosphate carrier; (3) the combined action of both the Na+ (out/in) and H+ (in/out) gradients on the phosphate carrier contribute to regulate efficiently the re-absorption of phosphate.

scholarly journals Effects of insulin and glucose on renal phosphate reabsorption: interactions with dietary phosphate.

1992 ◽  
Vol 2 (11) ◽  
pp. 1593-1600
Author(s):  
M Allon
Keyword(s):  
Phosphate Uptake ◽  
Membrane Vesicles ◽  
Phosphate Transport ◽  
Tubular Reabsorption ◽  
Insulin Deficiency ◽  
Renal Brush Border Membrane ◽  
Renal Phosphate Reabsorption ◽  
Catabolic State ◽  
Dietary Phosphate ◽  
Phosphate Depletion

Both insulin deficiency and glycosuria are known to inhibit the tubular reabsorption of phosphate. This inhibition has previously been evaluated either in the fasted state or on a normal phosphate diet. The goal of this study was to evaluate how dietary phosphate depletion affected the relative effects of insulin deficiency and glycosuria on the tubular reabsorption of phosphate. Rats were maintained on either a low- (0.03%) or normal (0.8%) phosphate diet. After 5 days, one half of the animals in each group received streptozotocin to induce short-term insulin deficiency, whereas the other half received vehicle alone. Two days later, sodium-dependent phosphate uptake by renal brush border membrane vesicles (BBMV) was evaluated in each of the four experimental groups. The effect of glucose on phosphate uptake was determined by the addition of varying concentrations of glucose (between 0 and 32 mmol/L) to the extravesicular transport fluid. BBMV phosphate uptake was about threefold higher in the nondiabetic rats fed a low-phosphate diet as compared with the nondiabetic animals maintained on a normal phosphate diet. In rats maintained on a low-phosphate diet, streptozotocin treatment prevented the increase in BBMV phosphate transport; in contrast, in animals fed a normal phosphate diet, streptozotocin treatment had no effect on BBMV phosphate transport. Extravesicular glucose significantly inhibited phosphate transport in a dose-related manner, regardless of dietary phosphate or insulin status. Because fasting mimics the catabolic state associated with insulin deficiency, BBMV phosphate transport was also measured in rats fasted for 48 h after the administration of streptozotocin or vehicle.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Phosphate transport by rat intestinal basolateral-membrane vesicles

1987 ◽  
Vol 243 (3) ◽  
pp. 641-646 ◽  
Author(s):  
F K Ghishan ◽  
K Kikuchi ◽  
N Arab
Keyword(s):  
Membrane Potential ◽  
Phosphate Uptake ◽  
Basolateral Membrane ◽  
Membrane Vesicles ◽  
Phosphate Transport ◽  
Basolateral Membrane Vesicles ◽  
Transport Studies ◽  
Na Effect ◽  
Static Head ◽  
Phosphate Carrier

The characteristics of phosphate transport across intestinal basolateral membranes of the rat were determined by using enriched preparations in which uphill Na+-dependent D-glucose transport could not be demonstrated, but ATP-dependent Ca2+ transport was present. Phosphate transport was saturable, Na+-dependent and exhibited Michaelis-Menten kinetics. Vmax. was 51.1 +/- 4.2 pmol/10 s per mg of protein and Km was 14 +/- 3.9 microM. The transport process was electroneutral. Tracer-exchange experiments and counter-transport studies confirmed the presence of a Na+-Pi carrier at the basolateral membrane. The presence of inside-positive membrane potential did not enhance phosphate uptake, indicating that the Na+ effect is secondary to the presence of the Na+-Pi carrier rather than an induction of positive membrane potential. The stoichiometry of this carrier at pH 7.4 was 2 Na+:1 phosphate, as shown by direct studies utilizing the static-head method. These studies are the first to determine the presence of a phosphate carrier at the basolateral membrane.

scholarly journals Effect of dietary phosphate intake on phosphate transport by isolated rat renal brush-border vesicles

1979 ◽  
Vol 180 (3) ◽  
pp. 465-470 ◽  
Author(s):  
Reinhard Stoll ◽  
Rolf Kinne ◽  
Heini Murer
Keyword(s):  
Proximal Tubule ◽  
Brush Border ◽  
Dry Matter ◽  
Brush Border Membrane ◽  
Phosphate Uptake ◽  
Membrane Vesicles ◽  
Phosphate Transport ◽  
Phosphate Intake ◽  
Dietary Phosphate ◽  
Renal Brush Border

Renal brush-border membrane vesicles isolated from rats kept for 6–8 weeks on a low-phosphate diet (0.15% of dry matter) showed a markedly faster Na+-dependent phosphate uptake than did membrane vesicles isolated from animals kept on a high-phosphate diet (2% of dry matter). Phosphate-uptake rate by brush-border membrane vesicles isolated from animals on a low-phosphate diet remained significantly increased after acute parathyroidectomy. Dietary adaptation was also observed in animals that had been parathyroidectomized before exposure to the different diets. In animals on the low-phosphate diet parathyrin administration inhibited phosphate uptake by brush-border vesicles only if the animals were repleted with Pi (5ml of 20mm-NaH2PO4) 1h before being killed. After acute phosphate loading and parathyrin administration the difference in the transport rate between the two dietary groups remained statistically significant. The results suggest that the adaptation of proximal-tubule phosphate transport to dietary intake of phosphate is reflected in the Na+/phosphate co-transport system located in the luminal membrane of the proximal-tubule cell. Since the dietary effects on phosphate transport by brush-border membranes are only partially reversed by acute changes in parathyrin concentration and are also observed in chronically parathyroidectomized animals, the adaptation of the Na+/phosphate co-transport system to dietary phosphate intake seems to involve an additional mechanism independent of parathyrin.

Effect of dietary phosphate on transport properties of pig renal microvillus vesicles

1980 ◽  
Vol 239 (4) ◽  
pp. F352-F359 ◽  
Author(s):  
Paula Q. Barrett ◽  
Joseph M. Gertner ◽  
Howard Rasmussen
Keyword(s):  
Phosphate Uptake ◽  
Membrane Vesicle ◽  
Membrane Vesicles ◽  
Phosphate Transport ◽  
Transport Systems ◽  
Sodium Gradient ◽  
Microvillus Membrane ◽  
Dietary Phosphate ◽  
Dependent Transport ◽  
High Phosphate

Dietary phosphate manipulation results in stable adaptive changes in the transport functions of microvillus membrane vesicles isolated from pig renal cortex. When assayed under sodium gradient conditions, phosphate uptake is enhanced 200–400% in vesicles prepared from animals maintained on a low-phosphate diet (0.22%) compared to high-phosphate diet controls (0.82%). When transport is assayed in sodium preequilibrated vesicles, a 100% enhancement of phosphate uptake is demonstrable. Stimulation of phosphate uptake into low-phosphate diet vesicles after the imposition of a sodium chloride gradient is equivalent if uptake is measured at pH 6.0 or 8.0 and can be kinetically characterized as resulting from a Vmax alteration in the phosphate transport system. Microvillus membrane vesicle phosphate transport is maximally stimulated after only 2 days of dietary deprivation. Although a longer period (1 and 2 wk) of phosphate restriction does not further stimulate phosphate transport, it does result in an inhibition of other sodium gradient-dependent transport systems (glucose, alanine). phosphate transport; phosphate restriction; glucose transport; brush-border vesicles Submitted on October 22, 1979 Accepted on April 25, 1980

Renal adaptation to phosphate load in the acutely thyroparathyroidectomized rat: rapid alteration in brush border membrane phosphate transport

1984 ◽  
Vol 246 (4) ◽  
pp. F488-F494 ◽  
Author(s):  
L. Cheng ◽  
C. Dersch ◽  
E. Kraus ◽  
D. Spector ◽  
B. Sacktor
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Phosphate Uptake ◽  
Membrane Vesicles ◽  
Phosphate Transport ◽  
Uptake System ◽  
Renal Adaptation ◽  
22Na Uptake ◽  
Isolated Membrane Vesicles

The sustained in vivo infusion of phosphate into thyroparathyroidectomized rats resulted, after 1 h, in a marked decrease in net phosphate reabsorption, even though the plasma concentration of phosphate continued to rise. This response to phosphate infusion was expressed at the level of the proximal tubule brush border membrane. Within 40 min of the initiation of the infusion the Na+-dependent phosphate uptake system in isolated membrane vesicles was decreased. Phosphate uptake in the absence of Na+, Na+-dependent D-glucose uptake, and 22Na+ uptake were not affected. These findings demonstrate the locus of this parathyroid hormone-independent adaptation and indicate the rapidity with which the membrane transport system is regulated.

Effect of temperature and pH on phosphate transport through brush border membrane vesicles in rats

1984 ◽  
Vol 62 (2) ◽  
pp. 229-234 ◽  
Author(s):  
Michèle G. Brunette ◽  
Richard Beliveau ◽  
Meanthan Chan
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Phosphate Uptake ◽  
Membrane Vesicles ◽  
Phosphate Transport ◽  
Mean Value ◽  
Brush Border Membrane Vesicles ◽  
Effect Of Temperature ◽  
Total Phosphate ◽  
Renal Brush Border Membrane

The kinetics of sodium gradient dependent phosphate uptake by the renal brush border membrane vesicles of the rat have been studied under various conditions of temperature and pH. From 7 to 30 °C the Lineweaver-Burk plots are linear, and the apparent Km progressively increases from 54 to 91 μM. Above 30 °C, the apparent Km continues to increase to reach 135 μM at 40 °C, but a break is observed in the Lineweaver-Burk plots at the substrate concentration of 300 μM. The existence of this break, confirmed by the Eadie-Hofstee plot supports the hypothesis of a dual mechanism of phosphate transport, one for low concentrations of substrate with a Km of 100 μM and the other for high concentrations with a Km of approximately 240 μM. When the two components of the Eadie-Hofstee plot are analyzed according to a nonlinear regression program, these two values of Km become 70 μM and 1.18 mM, respectively. The Vmax continuously increases with temperature. However, the Arrhenius plot (In Vmax vs. 1/Tk) shows an abrupt discontinuity at 23 °C. pH experiments were performed at 35 °C. In the absence of a proton gradient, increasing the pH from 6.5 to 7.5 and 8.5 decreases the apparent Km from 341 to 167 and 94 μM, respectively. When only the divalent form of phosphate is considered as the substrate, the apparent Km does not vary anymore with the pH and remains around the mean value of 105 μM. The uniformity of the apparent Km for the total phosphate uptake, when only the divalent phosphate is considered as being the substrate, suggests that this divalent form is the only one which is transported. Whatever the substrate considered, total phosphate or divalent phosphate, the highest Vmax is obtained at pH 7.5 which probably approximates the optimum pH inside the vesicles for the phosphate uptake.

Effect of pH on phosphate transport in rat renal brush border membrane vesicles

1985 ◽  
Vol 248 (5) ◽  
pp. F705-F710 ◽  
Author(s):  
M. Amstutz ◽  
M. Mohrmann ◽  
P. Gmaj ◽  
H. Murer
Keyword(s):  
Transport System ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Phosphate Uptake ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Effect Of Ph ◽  
High Sodium ◽  
Renal Brush Border Membrane ◽  
Renal Brush Border

The initial linear rate of phosphate uptake was analyzed in rat renal brush border membrane vesicles. An increase in medium pH from 6.0 to 8.0 increased the sodium gradient-dependent phosphate uptake about 20-fold. Sodium-independent phosphate uptake was not altered in this pH range. At pH 7.4 an intravesicular acid pH stimulated the initial linear uptake rate (20-25%). The apparent Km for sodium increased from about 100 to 200 mM when pH was decreased from 7.4 to 6.4. The Hill coefficient for sodium interaction was close to 2 and was unaffected by pH. Increasing external sodium reduced the apparent Km of the transport system for phosphate independent of pH. Variations of phosphate concentration had no influence on the apparent Km for sodium. At high sodium concentrations, small effects (20-30%) of pH on the apparent Vmax of the transport system were found; measured at saturating sodium concentrations, the apparent Km values calculated on the basis of total phosphate were increased (50-60%) when pH was decreased from 7.4 to 6.4. The data indicate that the major effect of pH is to modify the interaction of the transport system with sodium. At nonsaturating sodium concentrations, this resulted indirectly in a reduction in the affinity for phosphate related to a different occupancy of the sodium binding site. The differences of transport rate at low phosphate and high sodium concentrations could be explained by preferential transport of divalent phosphate as well as by pH effects on other carrier properties.

Kinetic model for phosphate transport in renal brush-border membranes

1988 ◽  
Vol 254 (3) ◽  
pp. F329-F336 ◽  
Author(s):  
R. Beliveau ◽  
J. Strevey
Keyword(s):  
Brush Border ◽  
Rat Kidney ◽  
Membrane Vesicles ◽  
Phosphate Transport ◽  
Kidney Cortex ◽  
Binary Complex ◽  
Rat Kidney Cortex ◽  
First Time ◽  
Phosphate Influx ◽  
Phosphate Carrier

Phosphate transport was studied in brush-border membrane vesicles purified from rat kidney cortex. Influx and efflux were strongly dependent on the presence of cis sodium; the rate of efflux, calculated by linear regression performed on the first time points, was much lower than the rate of influx (0.044 vs. 0.198 pmol.microgram protein-1.s-1). Trans phosphate had a stimulatory effect on phosphate influx (145% stimulation at 10 mM phosphate trans, with 0.2 mM phosphate cis). Trans phosphate was, however, inhibitory for phosphate efflux (89% inhibition at 10 mM phosphate trans). Trans effects of sodium were also studied. With 200 mM trans sodium, we observed 73% inhibition of phosphate influx and 60% inhibition of phosphate efflux. Studies involving sodium and phosphate present at the same time as trans substrates showed that the trans inhibition of phosphate influx by sodium could be completely reversed by trans phosphate. Trans inhibition of phosphate efflux by phosphate was not additive to the inhibition caused by sodium. Addition of trans phosphate had a stimulatory effect on sodium-independent influx, indicating that the binary complex (C-P) could translocate in efflux. These results indicate that the renal phosphate carrier presents a random binding scheme for the intra- and extravesicular sides of the membrane.

pH gradient-stimulated phosphate transport in outer medullary brush-border membranes

1989 ◽  
Vol 257 (4) ◽  
pp. F639-F648
Author(s):  
G. A. Quamme ◽  
J. J. Walker ◽  
T. S. Yan
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Phosphate Uptake ◽  
Membrane Vesicles ◽  
Phosphate Transport ◽  
Brush Border Membrane Vesicles ◽  
Ph Gradient ◽  
Disulfonic Acid ◽  
Maximal Velocity ◽  
Medullary Tissue

Phosphate transport was studied in brush-border membrane vesicles prepared from outer medullary tissue of the porcine kidney. Phosphate uptake studies were performed in the absence of sodium at 21 degrees C. A 1.2- to 12-fold overshoot, above equilibrium values, was present with intracellular pH (pHin) equal to 8.0 and extracellular pH (pHout) equal to 6.5, which was not evident at pHin = pHout. Concentration-dependence of the pH-stimulate uptake was determined by the difference of uptake in the absence of a pH gradient (pHin = pHout) from that in the presence of a pH gradient over a large range of phosphate concentrations. The uptake was consistent with a single facilitative system characterized by apparent kinetic parameters; with Michaelis constant 149 +/- 11 microM and maximal velocity 4.9 +/- 0.4 nmol.mg protein-1.min-1, n = 3. Phosphate uptake was inhibited by the stilbene derivative 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid with a mean inhibition constant (Ki) value of 0.15 mM (n = 2). In addition, pH gradient-stimulated phosphate uptake was sensitive to furosemide and bumetanide; Ki values of 0.50 +/- 0.05 and 0.11 +/- 0.04 mM, respectively. Arsenate (1 mM) and phosphonoformate (1 mM) inhibited pH-dependent phosphate uptake, whereas sulfate (5 mM), bicarbonate (25 mM), and chloride (100 mM) were without effect, indicating that the transport system is relatively specific to phosphate and its close analogues. pH gradient-stimulated phosphate uptake was not influenced by potassium-diffusional gradients. The data provide evidence for a facilitative process in brush-border membrane vesicles isolated from outer medullary tissue of the pig kidney that is capable of transporting phosphate in the absence of sodium.

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