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.

Regulation of Na+-Pi cotransport by 1,25-dihydroxyvitamin D3 in rabbit duodenal brush-border membrane

1982 ◽  
Vol 242 (5) ◽  
pp. G533-G539 ◽  
Author(s):  
B. Hildmann ◽  
C. Storelli ◽  
G. Danisi ◽  
H. Murer
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Precipitation Method ◽  
Dihydroxyvitamin D3 ◽  
1,25 Dihydroxyvitamin D3 ◽  
Pi Transport ◽  
Sodium Dependent ◽  
Cotransport System

Brush-border membrane vesicles were isolated from rabbit duodenum by a Mg2+ precipitation method, and phosphate transport was analyzed by a rapid filtration technique. Uptake of inorganic phosphate (Pi) was stimulated by an inwardly directed sodium gradient, indicating the operation of a Na-Pi cotransport system in brush-border membrane vesicles. Treatment of the animals with ethane-1-hydroxy-1,1-diphosphonate (EHDP), which is known to decrease the circulating levels of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], reduced within 3 days the sodium-dependent Pi transport in the brush-border vesicles. Injections of 1,25(OH)2D3 into rabbits increased within 9 h the sodium-dependent Pi transport in membranes from EHDP-treated animals as well as in untreated ones. The Na-D-glucose cotransport system appeared to be unaffected by these maneuvers. These results suggest that the Na-Pi cotransport system is an important site of regulation of intestinal transepithelial Pi transport by 1,25(OH)2)D3.

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.

D-glucose and L-leucine transport by human intestinal brush-border membrane vesicles

1989 ◽  
Vol 256 (3) ◽  
pp. G618-G623 ◽  
Author(s):  
J. M. Harig ◽  
J. A. Barry ◽  
V. M. Rajendran ◽  
K. H. Soergel ◽  
K. Ramaswamy
Keyword(s):  
Small Intestine ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Transport Systems ◽  
Intestinal Brush Border Membrane ◽  
High Affinity ◽  
Intestinal Brush Border ◽  
Sodium Gradient

This study utilized intestinal brush-border membrane vesicles obtained from organ donor intestine to characterize the absorption of D-glucose and L-leucine in the human intestine. Both D-glucose and L-leucine were taken up by sodium gradient-dependent active transport along the entire length of the small intestine. The relative magnitude of transport for both substrates under sodium gradient conditions followed the order distal jejunum greater than proximal jejunum greater than distal ileum. The number of carrier systems in these brush-border membrane vesicles was estimated by Eadie-Hofstee plot analysis. This analysis revealed that L-leucine was actively transported via a single high-affinity transport system for the length of the human small intestine. In contrast, the transport of D-glucose occurred via a high-affinity system along the length of the intestine and via a low-affinity, high-flux transport system that was limited to the proximal intestine. Both glucose transport systems were sodium dependent and phlorizin sensitive. The locations and apparent kinetic parameters of these transport systems indicated that these systems function efficiently in vivo as important mechanisms for carbohydrate and protein assimilation in humans. The presence of these active transport systems along the entire small intestine explains the formidable capacity for carbohydrate and protein assimilation in humans.

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