scholarly journals Transport System by Brush Border Membrane Vesicles in Spontaneously Hypertensive Rats

1987 ◽  
Vol 28 (4) ◽  
pp. 596-596
Author(s):  
Kiyoshi Hirano ◽  
Masaki Nagasawa ◽  
Mamoru Yokomatsu ◽  
Hikaru Koide
Keyword(s):  
Transport System ◽  
Brush Border ◽  
Spontaneously Hypertensive Rats ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive

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.

Lysine transport by brush-border membrane vesicles of eel intestine: interaction with neutral amino acids

1990 ◽  
Vol 259 (6) ◽  
pp. R1181-R1188 ◽  
Author(s):  
S. Vilella ◽  
G. A. Ahearn ◽  
G. Cassano ◽  
M. Maffia ◽  
C. Storelli
Keyword(s):  
Amino Acids ◽  
Transport System ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Hill Coefficient ◽  
European Eel ◽  
Diffusional Permeability ◽  
Wide Range

L-[3H]lysine uptake was measured in brush-border membrane vesicles prepared from intestinal mucosa of the European eel Anguilla anguilla. Lysine uptake occurred via 1) a nonsaturable component with an apparent diffusional permeability (P) of 0.58 microliter.mg protein-1.min-1,2) a Na-dependent transport system [half-saturation constant (Kapp) 0.16 mM, maximal transport rate (Jmax) 3.57 nmol.mg protein-1.min-1]; 3) a Na-independent transport system (Kapp 0.17 mM, Jmax 2.77 nmol.mg protein-1.min-1). Both carrier-mediated processes were accelerated by the presence of an intravesicular negative membrane potential. Hill analysis of L-lysine influx, over a wide range of external Na concentrations, resulted in a Hill coefficient (n) of approximately 2, suggesting that two or more Na ions may be associated with amino acid transport. The inhibition of lysine uptake by other amino acids was studied. Na-dependent lysine uptake was competitively inhibited by proline [inhibitory constant (Ki) approximately 2 mM] and may occur by a system specific for cationic amino acids. Na-independent lysine uptake was competitively inhibited by alanine (Ki approximately 1 mM) and may occur by a classic L system.

Ca2+ transport processes of lobster hepatopancreatic brush-border membrane vesicles

1996 ◽  
Vol 199 (5) ◽  
pp. 1195-1208 ◽  
Author(s):  
Z Zhuang ◽  
G Ahearn
Keyword(s):  
Epithelial Cells ◽  
Transport System ◽  
Divalent Cation ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Homarus Americanus ◽  
Transport Processes ◽  
Brush Border Membrane Vesicles ◽  
Carrier Mediated Transport

45Ca2+ uptake by hepatopancreatic brush-border membrane vesicles of Atlantic lobster (Homarus americanus) occurred by a combination of three independent processes: (1) an amiloride-sensitive carrier-mediated transport system; (2) an amiloride-insensitive carrier-mediated transport system; and (3) a verapamil-inhibited channel process responsive to transmembrane potential. Both carrier-mediated processes were antiporters and capable of exchanging external Ca2+ with intravesicular Na+ or H+. The kinetic parameters of both carrier-mediated processes have been reported previously. External amiloride and Zn2+ were both competitive inhibitors of 45Ca2+ influx, reducing entry of the divalent cation at a single binding site with Ki values of 370 µmol l-1 for amiloride and 940 µmol l-1 for Zn2+. It is concluded that the mechanisms controlling Ca2+ entry into hepatopancreatic epithelial cells include a previously reported electrogenic 2Na+/1H+ antiporter, an electroneutral 2Na+/1Ca2+ antiporter and a verapamil-sensitive Ca2+ channel, which might also be used for the entry of Zn2+ and possibly other heavy metals. Evidence from an equilibrium-shift experiment, based on the thermodynamics of a coupled transport process, suggested that both monovalent (Na+) and divalent (Ca2+ and Zn2+) cations may enter hepatopancreatic epithelial cells through a common carrier-mediated transport protein. This suite of hepatopancreatic brush-border Ca2+ transport processes qualitatively resembles that previously reported for the luminal membrane of lobster antennal glands and suggests that crustacean epithelial cells from different organs may handle this divalent cation by similar means.

Dicarboxylate transport in renal basolateral and brush-border membrane vesicles

1992 ◽  
Vol 70 (1) ◽  
pp. 106-112 ◽  
Author(s):  
Yong Keun Kim ◽  
Jin Sup Jung ◽  
Sang Ho Lee
Keyword(s):  
Transport System ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Basolateral Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Rabbit Kidney ◽  
Substrate Affinity ◽  
Dicarboxylate Transport ◽  
Overshoot Phenomenon

Characteristics of succinate transport were determined in basolateral and brush-border membrane vesicles (BLMV and BBMV, respectively) isolated in parallel from rabbit renal cortex. The uptake of succinate was markedly stimulated by the imposition of an inwardly directed Na+ gradient, showing an "overshoot" phenomenon in both membrane preparations. The stimulation of succinate uptake by an inwardly directed Na+ gradient was not significantly affected by pH clamp or inhibition of Na+–H+ exchange. The Na+-dependent and -independent succinate uptakes were not stimulated by an outwardly directed pH gradient. The Na dependence of succinate uptake exhibited sigmoidal kinetics, with Hill coefficients of 2.17 and 2.38 in BLMV and BBMV, respectively. The Na+-dependent succinate uptake by BLMV and BBMV was stimulated by a valinomycin-induced inside-negative potential. The Na+-dependent succinate uptake by BLMV and BBMV followed a simple Michaelis–Menten kinetics, with an apparent Km of 22.20 ± 4.08 and 71.52 ± 0.14 μM and a Vmax of 39.0 ± 3.72 and 70.20 ± 0.96 nmol/(mg·min), respectively. The substrate specificity and the inhibitor sensitivity of the succinate transport system appeared to be very similar in both membranes. These results indicate that both the renal brush-border and basolateral membranes possess the Na+-dependent dicarboxylate transport system with very similar properties but with different substrate affinity and transport capacity.Key words: dicarboxylate transport, brush border membrane, basolateral membrane, inhibitors, rabbit kidney.

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