Sodium-dependent sulfate transport in renal outer cortical brush border membrane vesicles

1984 ◽  
Vol 247 (5) ◽  
pp. F793-F798 ◽  
Author(s):  
R. J. Turner
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Sodium Concentration ◽  
Brush Border Membrane Vesicles ◽  
Sulfate Transport ◽  
Dependent Component ◽  
Sulfate Flux ◽  
Sodium Dependent ◽  
Stimulation Of

The transport of sulfate into outer cortical brush border membrane vesicles (early proximal tubule) was studied. Sulfate uptake was markedly enhanced by sodium and slightly enhanced by lithium but showed no stimulation by other monovalent cations tested. Kinetic analysis of the sodium-dependent component of sulfate flux indicated a single transport system obeying Michaelis-Menten kinetics. Studies of the dependence of sulfate flux on sodium concentration indicated that more than one sodium ion was involved in the sulfate transport event. Although sulfate influx was found to be stimulated by negative intravesicular potentials, evidence is presented that sodium/sulfate cotransport is nevertheless an electroneutral event presumably involving 2 Na+ per SO2-4. Under zero trans sodium conditions sodium-dependent sulfate influx was stimulated by the presence of intravesicular unlabeled sulfate (trans stimulation); however, a similar stimulation of sulfate efflux by the presence of unlabeled extravesicular sulfate was not observed. These latter results are consistent with an ordered binding scheme for the transporter, with sulfate binding before sodium on the extravesicular (urine) surface and dissociating before sodium on the intravesicular (cytosolic) surface.

Sodium-dependent succinate transport in renal outer cortical brush border membrane vesicles

1983 ◽  
Vol 245 (3) ◽  
pp. F374-F381 ◽  
Author(s):  
Y. Fukuhara ◽  
R. J. Turner
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Direct Evidence ◽  
Positive Charge ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Dependent Component ◽  
Sodium Dependent ◽  
Coupling Stoichiometry ◽  
Transport Site

The transport of succinate into outer cortical brush border membrane vesicles (early proximal tubule) was studied. Succinate is taken up into an osmotically active space and exhibits the same distribution volume and the same degree of nonspecific binding and trapping as D-glucose. Succinate uptake is markedly enhanced by sodium and slightly enhanced by lithium but shows no stimulation by other monovalent cations tested. Kinetic analysis of the sodium-dependent component of succinate flux indicates a single transport site obeying Michaelis-Menten kinetics (Km = 1 mM and Vmax = 50 nmol X min -1 X mg protein -1 as measured under zero trans conditions at 100 mM NaCl and 28 degrees C with delta psi = 0). Direct evidence is given that succinate transport is coupled to sodium and is rheogenic, involving the net transfer of positive charge. The sodium:succinate coupling stoichiometry is found to be 2:1 by two independent methods.

Effect of pH on phosphate transport into intestinal brush-border membrane vesicles

1984 ◽  
Vol 246 (2) ◽  
pp. G180-G186 ◽  
Author(s):  
G. Danisi ◽  
H. Murer ◽  
R. W. Straub
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Ph Dependence ◽  
Membrane Vesicles ◽  
Sodium Concentration ◽  
Brush Border Membrane Vesicles ◽  
Alkaline Ph ◽  
Effect Of Ph ◽  
Ph Values ◽  
Sodium Dependent

The effect of pH on the rate of phosphate (Pi) uptake was studied in rabbit duodenal brush-border membrane vesicles. Pi uptake was found to be sodium dependent at all pH values tested (5.7-8.1). Further, the rate of Pi uptake depended on pH; for instance, with 100 mM external sodium, reducing the pH from 8.1 to 6.8 or 5.7 doubled the rate of Pi influx. At 100 mM external sodium, experiments under initial rate conditions, carried out with varying Pi concentrations and at pH values of 6, 6.8, or 7.6, showed that sodium-dependent Pi uptake was saturable at the three pH values tested; the apparent Km expressed in function of total Pi was not dependent on pH. Vmax was not affected between pH 6 and 6.8 but was significantly reduced at pH 7.6. Lowering external sodium lowered Vmax at all pH values investigated. At acid and alkaline pH the rate of Pi uptake was a sigmoidal function of the external sodium concentration. Hill coefficients, calculated from these experiments, exceeded unity and were unaffected by pH. At saturating sodium concentrations, the rate of Pi uptake was higher at pH 6 than at pH 7.6. The [Na]0.5 was lower at pH 7.6 than at pH 6. Further, sodium-dependent Pi uptake appeared to be electrogenic at acid and alkaline pH. It is concluded that the pH dependence of intestinal Pi transport is not an expression of preferential transport of monovalent or divalent phosphate. The pH dependence appears to reflect properties of the sodium-phosphate cotransport mechanism and is in part related to changes in the affinity of the transport system for sodium.

Sodium-pyrazinoate cotransport in rabbit renal brush border membrane vesicles

1985 ◽  
Vol 249 (3) ◽  
pp. F400-F408 ◽  
Author(s):  
M. Manganel ◽  
F. Roch-Ramel ◽  
H. Murer
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Organic Anion ◽  
Membrane Vesicles ◽  
Sodium Concentration ◽  
Brush Border Membrane Vesicles ◽  
Renal Brush Border Membrane ◽  
Sodium Dependent ◽  
Dependent Transport ◽  
Renal Brush Border

Pyrazinoate (PZA) is an organic anion actively reabsorbed and secreted in the mammalian kidney. In experiments with rabbit renal brush border membrane vesicles, we characterized a sodium-PZA cotransport mechanism that could be involved in reabsorption. An inwardly directed sodium gradient stimulated the influx of PZA. The sodium-dependent transport was electroneutral, suggesting a 1:1 stoichiometry. The kinetic constants for sodium-PZA cotransport were measured under initial linear flux and zero trans conditions for both sodium and PZA. The apparent Km for sodium was about 60 mM. At 90 mM sodium the apparent Km for PZA was about 1.1 mM; increasing the sodium concentration augmented the apparent affinity for PZA. Cis inhibition of sodium-dependent PZA uptake was observed by the addition of nicotinate, lactate, probenecid, succinate, beta-hydroxybutyrate, and salicylate. Urate had no effect. [14C]PZA uptake was trans stimulated by PZA itself, lactate, and nicotinate. PZA shares a transport system(s) involved in the proximal tubular reabsorption of these two anions.

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.

Indirect coupling of urate and p-aminohippurate transport to sodium in human brush-border membrane vesicles

1996 ◽  
Vol 270 (1) ◽  
pp. F61-F68 ◽  
Author(s):  
F. Roch-Ramel ◽  
B. Guisan ◽  
L. Schild
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Indirect Coupling ◽  
Sodium Gradient ◽  
Beta Hydroxybutyrate ◽  
Sodium Cotransport ◽  
Stimulation Of

[14C]urate and p-[14C]aminohippurate (PAH) uptake by human brush-border membrane vesicles (BBMV) were measured in the presence of an inwardly oriented sodium gradient. No direct sodium cotransport was observed. Indirect [14C]urate coupling to sodium transport was demonstrated by cis-stimulation of [14C]urate with nicotinate or pyrazinoate (PZA) in the extravesicular medium but not by adding lactate, alpha-ketoglutarate, or beta-hydroxybutyrate. Indirect sodium coupling of [14C]PAH uptake was observed only when alpha-ketoglutarate was added to the extravesicular medium, a mechanism similar to that of basolateral membranes. The ability for PZA (and nicotinate) to cis-stimulate urate uptake was correlated with a high apparent affinity for the urate/anion exchanger. In urate-loaded vesicles, for identical medium concentrations, [14C]PZA uptake via the urateanion exchanger was 10 times higher than [14C]lactate uptake. Such high PZA affinity for the urate exchanger, working in parallel with PZA sodium cotransport can account for the stimulation of urate reabsorption by PZA in vivo.

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