Mechanisms of phosphate uptake into brush-border membrane vesicles from goat jejunum

1996 ◽  
Vol 166 (3) ◽  
pp. 230-240 ◽  
Author(s):  
B. Schr�der ◽  
G. Breves
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Phosphate Uptake ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles

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.

Role of Alkaline Phosphatase in Phosphate Uptake into Brush Border Membrane Vesicles from Human Intestinal Mucosa

1985 ◽  
Vol 97 (5) ◽  
pp. 1461-1466 ◽  
Author(s):  
Kazuyuki HIRANO ◽  
Yuichi IIIZUMI ◽  
Yukio MORI ◽  
Kazumi TOYOSHI ◽  
Mamoru SUGIURA ◽  
...  
Keyword(s):  
Alkaline Phosphatase ◽  
Intestinal Mucosa ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Phosphate Uptake ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles

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.

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.

scholarly journals Effect of parathyrin on the transport properties of isolated renal brush-border vesicles

1978 ◽  
Vol 172 (1) ◽  
pp. 49-56 ◽  
Author(s):  
C Evers ◽  
H Murer ◽  
R Kinne
Keyword(s):  
Cyclic Amp ◽  
Transport Properties ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Phosphate Uptake ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Transport Systems ◽  
Precipitation Method ◽  
Dibutyryl Cyclic Amp

The transport properties of brush-border membrane vesicles isolated by a calcium-precipitation method from the renal cortex of normal and parathyrin (parathyroid hormone)-treated rats were studied by a rapid-filtration technique. Parathyrin elicited a dose-dependent decrease in the Na+-dependent phosphate uptake by the brush-border membrane vesicles, but the uptake of D-glucose, Na+ and mannitol was not affected. A maximum inhibition of 30% was observed after the application of 30 U.S.P. units intramuscularly 1 h before the animals were killed. Intravenous infusion of dibutyryl cyclic AMP (0.5-1.5 MG) also decreased the phosphate uptake by the brush-border vesicles. Both dibutyryl cyclic AMP and parathyrin were ineffective when added in vitro to brush-border membrane vesicles isolated from normal rats. These data suggest that parathyrin exerts its action on the phosphate reabsorption in the renal proximal tubule by affecting the Na+/phosphate co-transport system in the brush-border membrane. The effects of parathyrin on Na+ and glucose transport, however, seem to be due to alterations to the driving forces for transport and not to the brush-border transport systems.

Low-affinity transport of pyroglutamyl-histidine in renal brush-border membrane vesicles

1989 ◽  
Vol 257 (5) ◽  
pp. C971-C975 ◽  
Author(s):  
H. A. Skopicki ◽  
K. Fisher ◽  
D. Zikos ◽  
G. Flouret ◽  
D. R. Peterson
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Proximal Tubular Cells ◽  
Tubular Cells ◽  
Luminal Membrane ◽  
Renal Brush Border Membrane ◽  
Proximal Tubular ◽  
Renal Brush Border

These studies were performed to determine if a low-affinity carrier is present in the luminal membrane of proximal tubular cells for the transport of the dipeptide, pyroglutamyl-histidine (pGlu-His). We have previously described the existence of a specific, high-affinity, low-capacity [transport constant (Kt) = 9.3 X 10(-8) M, Vmax = 6.1 X 10(-12) mol.mg-1.min-1] carrier for pGlu-His in renal brush-border membrane vesicles. In the present study, we sought to demonstrate that multiple carriers exist for the transport of a single dipeptide by determining whether a low-affinity carrier also exists for the uptake of pGlu-His. Transport of pGlu-His into brush-border membrane vesicles was saturable over the concentration range of 10(-5)-10(-3) M, yielding a Kt of 6.3 X 10(-5) M and a Vmax of 2.2 X 10(-10) mol.mg-1.min-1. Uptake was inhibited by the dipeptides glycyl-proline, glycyl-sarcosine, and carnosine but not by the tripeptide pyroglutamyl-histidyl-prolinamide. We conclude that 1) pGlu-His is transported across the luminal membrane of the proximal tubule by multiple carriers and 2) the lower affinity carrier, unlike the higher affinity carrier, is nonspecific with respect to other dipeptides.

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