scholarly journals Na+-H+ exchange in luminal-membrane vesicles from rabbit proximal convoluted and straight tubules in response to metabolic acidosis

1986 ◽  
Vol 239 (2) ◽  
pp. 411-416 ◽  
Author(s):  
C Jacobsen ◽  
U Kragh-Hansen ◽  
M I Sheikh
Keyword(s):  
Metabolic Acidosis ◽  
Membrane Vesicles ◽  
Luminal Membrane ◽  
Straight Tubules ◽  
Pars Recta ◽  
Km Value ◽  
Experimental Approaches ◽  
And Control ◽  
Pars Convoluta ◽  
Filtration Technique

Na+-H+-exchanger activity of pars convoluta and pars recta luminal-membrane vesicles prepared from the proximal tubule of acidotic and control rabbits were assayed by a rapid-filtration technique and an Acridine Orange method. Both experimental approaches revealed the existence of an antiporter, sensitive to metabolic acidosis, in pars convoluta membrane vesicles. Kinetic data, obtained with the pH-sensitive dye, showed that the Km for Na+ transport was unchanged by acidosis, whereas Vmax. for exchanger activity was increased, on an average, by 44%. The fluorescence method, in contrast with the rapid-filtration technique, was able to detect exchanger activity in pars recta membrane vesicles. The Km value for the antiporter located in pars recta is comparable with that calculated for pars convoluta membrane vesicles. By contrast, the Vmax. of this exchanger is only about 25% of that found for pars convoluta. Furthermore, metabolic acidosis apparently does not increase Na+-H+-exchanger activity of pars recta luminal-membrane vesicles.

scholarly journals Renal transport of neutral amino acids. Cation-dependent uptake of l-alanine by luminal-membrane vesicles

1987 ◽  
Vol 248 (2) ◽  
pp. 533-538 ◽  
Author(s):  
K E Jørgensen ◽  
M I Sheikh
Keyword(s):  
Transport System ◽  
Membrane Vesicles ◽  
Transport Systems ◽  
Physiological Importance ◽  
High Affinity ◽  
Luminal Membrane ◽  
Alanine Transport ◽  
Pars Recta ◽  
Pars Convoluta ◽  
Filtration Technique

The characteristics of L-alanine transport in luminal-membrane vesicles isolated either from whole cortex or from pars convoluta or pars recta of rabbit proximal tubules were studied by a rapid filtration technique and by a spectrophotometric method. Uptake of L-alanine by vesicles from whole cortex was mediated by both Na+-dependent and Na+-independent, but electrogenic, processes. The nature, mechanism and tubular localization of the transport systems were studied by the use of vesicles derived from pars convoluta and pars recta. In vesicles from pars recta transport of L-alanine was strictly dependent on Na+ and occurred via a dual transport system, namely a high-affinity (half-saturation 0.14 mM) and a low-affinity system (half-saturation 9.6 mM). The cation-dependent but Na+-unspecific transport system for L-alanine was exclusively localized to the pars convoluta, which also contained an Na+-preferring system of intermediate affinity (half saturation 2.1 mM). A closer examination of the mechanism of transport of L-alanine in vesicles from pars convoluta revealed that an H+ gradient (extravesicular greater than intravesicular) can drive the transport of L-alanine into the vesicles both in the presence and in the absence of Na+. The physiological importance of various L-alanine transporters is briefly discussed.

scholarly journals Stoichiometric studies of β-alanine transporters in rabbit proximal tubule

1991 ◽  
Vol 277 (3) ◽  
pp. 891-894 ◽  
Author(s):  
H Jessen ◽  
M I Sheikh
Keyword(s):  
Indirect Evidence ◽  
Membrane Vesicles ◽  
Rabbit Kidney ◽  
Coupling Ratio ◽  
Beta Alanine ◽  
Luminal Membrane ◽  
Straight Tubules ◽  
Pars Recta ◽  
Pars Convoluta ◽  
Convoluted Tubules

The coupling ratio for the transport of beta-alanine and Na+, H+ and Cl- in luminal membrane vesicles isolated from proximal convoluted tubules (pars convoluta) and proximal straight tubules (pars recta) of rabbit kidney was examined. Indirect evidence indicates that 1 H+ and approx. 2 Na+, 1 Cl- (Na(+)-dependent, high-affinity) or 1 Na+ (Na(+)-dependent, low-affinity) are co-transported with beta-alanine in the pars convoluta. In pars recta, the two Na(+)-dependent transporters exhibited the same stoichiometric properties respectively as in pars convoluta.

Transport of L-proline by luminal membrane vesicles from pars recta of rabbit proximal tubule

1988 ◽  
Vol 254 (5) ◽  
pp. F628-F633
Author(s):  
H. Roigaard-Petersen ◽  
C. Jacobsen ◽  
M. I. Sheikh
Keyword(s):  
Active Site ◽  
Membrane Vesicles ◽  
Rabbit Kidney ◽  
Renal Transport ◽  
High Affinity ◽  
Luminal Membrane ◽  
Transport Studies ◽  
Straight Tubules ◽  
Pars Recta ◽  
Maximal Capacity

The mechanism of renal transport of L-proline by luminal membrane vesicles prepared from proximal straight tubules (pars recta) of rabbit kidney was investigated. The following picture emerges from transport studies: an electrogenic and Na+-requiring system confined to this region of nephron exists for transport of L-proline with a high affinity (Km = 0.16 mM) and low capacity (Vmax = 3.5 nmol.mg protein-1.15 S-1). Lowering the pH from 7.5 to 5.5 increased the affinity (Km lowered from 0.16 mM at pH 7.5 to 0.08 mM at pH 5.5) without changing the maximal capacity of this system. Modification of histidyl residues of the intact luminal membrane vesicles by diethyl-pyrocarbonate (DEP) completely abolished the transient renal accumulation of L-proline. Simultaneous presence of Na+ and L-proline (10 mM) protects against DEP inactivation of renal transport of radioactive L-proline. We propose that a histidyl residue may be at or close to the active site of L-proline transporter in vesicles from the pars recta.

Proton gradient-dependent renal transport of glycine: evidence for vesicle studies

1990 ◽  
Vol 258 (2) ◽  
pp. F388-F396 ◽  
Author(s):  
H. Roigaard-Petersen ◽  
H. Jessen ◽  
S. Mollerup ◽  
K. E. Jorgensen ◽  
C. Jacobsen ◽  
...  
Keyword(s):  
Transport System ◽  
Membrane Vesicles ◽  
Proton Gradient ◽  
Transport Systems ◽  
Rabbit Kidney ◽  
Renal Transport ◽  
High Affinity ◽  
Luminal Membrane ◽  
Pars Recta ◽  
Pars Convoluta

The characteristics of renal transport of glycine by luminal membrane vesicles isolated from either proximal convoluted part (pars convoluta) or proximal straight part (pars recta) of rabbit proximal tubule were investigated. In vesicles from pars convoluta two transport systems have been characterized: a Na(+)-dependent system with intermediate affinity (half-saturation 3.64 mM) and a Na(+)-independent system that, in the presence of H+ gradient (extravesicular greater than intravesicular), can accelerate the transport of glycine into these vesicles. This is the first demonstration of H(+)-glycine cotransport across the luminal membrane of rabbit kidney proximal convoluted tubule. By contrast, in membrane vesicles from pars recta, transport of glycine was strictly dependent on Na+ and occurred via a dual transport system, namely a high-affinity (half-saturation 0.34 mM) and a low-affinity system (half-saturation 8.56 mM). The demonstration of competition between the H(+)-gradient dependent uptake of glycine, L-alanine, and L-proline, but insignificant inhibition with L-phenylalanine in vesicles from pars convoluta suggests that glycine, L-proline, and L-alanine probably share a common proton gradient-dependent transport system. In vesicles from pars recta, the Na(+)-dependent uptake of glycine was inhibited by low concentrations of L-alanine and L-phenylalanine, whereas addition of L-proline to the incubation medium did not significantly alter the uptake of glycine, suggesting that the Na(+)-dependent high-affinity system for glycine located in pars recta is shared with the high-affinity L-alanine and L-phenylalanine but not L-proline transport system.

scholarly journals Renal transport of neutral amino acids. Demonstration of Na+-independent and Na+-dependent electrogenic uptake of l-proline, hydroxy-l-proline and 5-oxo-l-proline by luminal-membrane vesicles

1984 ◽  
Vol 220 (1) ◽  
pp. 25-33 ◽  
Author(s):  
H Røigaard-Petersen ◽  
M I Sheikh
Keyword(s):  
Amino Acids ◽  
Renal Cortex ◽  
Membrane Vesicles ◽  
Transport Systems ◽  
Acid Transport ◽  
Physiological Importance ◽  
High Affinity ◽  
Luminal Membrane ◽  
Pars Recta ◽  
Pars Convoluta

Uptake of L-proline, hydroxy-L-proline and 5-oxo-L-proline by luminal-membrane vesicles isolated either from whole cortex or from pars convoluta or pars recta of proximal tubules was studied by a spectrophotometric method. Uptake of L-proline and hydroxy-L-proline by vesicles from whole cortex was mediated by both Na+-dependent and Na+-independent, but electrogenic, processes, whereas transport of 5-oxo-L-proline in these vesicles was strictly Na+-dependent. Eadie-Hofstee analysis of saturation-kinetic data suggested the presence of multiple transport systems in luminal-membrane vesicles from whole renal cortex for the uptake of all these amino acids. Tubular localization of the transport systems was studied by the use of vesicles derived from pars convoluta and from pars recta. In pars recta transport of all three amino acids was strictly dependent on Na+ and occurred via a high-affinity system (half-saturation: 0.1-0.3 mM). Cation-dependent but Na+-unspecific transport of low affinity for L-proline and hydroxy-L-proline was exclusively localized to the pars convoluta, which also contained a Na+-preferring system of intermediate affinity (half-saturation: L-proline, 0.75 mM; hydroxy-L-proline, 1.3 mM). 5-Oxo-L-proline was transported by low-affinity and Na+-dependent systems in both pars convoluta and pars recta. Competition experiments revealed that transport systems for L-proline and hydroxy-L-proline are common, but indicated separate high-affinity transport systems for 5-oxo-L-proline and L-proline in luminal-membrane vesicles from pars recta. The physiological importance of the presence of various neutral amino acid-transport systems in different segments of the proximal tubule is discussed.

scholarly journals l-tryptophan uptake by segment-specific membrane vesicles from the proximal tubule of rabbit kidney

1992 ◽  
Vol 286 (1) ◽  
pp. 103-110 ◽  
Author(s):  
H Jessen ◽  
M I Sheikh
Keyword(s):  
Proximal Tubule ◽  
Basolateral Membrane ◽  
Membrane Vesicles ◽  
Rabbit Kidney ◽  
Basolateral Membrane Vesicles ◽  
Luminal Membrane ◽  
Transport Component ◽  
Pars Recta ◽  
Dependent Transport ◽  
Pars Convoluta

1. The mechanism of the renal transport of L-tryptophan by basolateral and luminal membrane vesicles prepared from either the pars convoluta or the pars recta of the rabbit proximal tubule was studied. The uptake of L-tryptophan by basolateral membrane vesicles from the pars convoluta was found to be an Na(+)-dependent transport event. The Na(+)-conditional influx of the amino acid was stimulated in the presence of an inwardly directed H+ gradient. Lowering the pH without an H+ gradient had no effect, indicating that L-tryptophan is co-transported with H+. 3. On the other hand, no transient accumulation of L-tryptophan was observed in the presence or absence of Na+ in basolateral membrane vesicles from the pars recta. 4. In luminal membrane vesicles from the pars recta, the transient Na(+)-dependent accumulation of L-tryptophan occurred via a dual transport system. In addition, an inwardly directed H+ gradient could drive the uphill transport of L-tryptophan into these vesicles in both the presence and the absence of an Na+ gradient. 5. By contrast, the uptake of L-tryptophan by luminal membrane vesicles from the pars convoluta was a strictly Na(+)-dependent and electrogenic transport process, mediated by a single transport component. 6. Investigation of the coupling ratio in luminal membrane vesicles suggested that 1 Na+:1 L-tryptophan are co-transported in the pars convoluta. In the pars recta, examination of the stoichiometry indicated that approx. 1 H+ and 2 Na+ (high affinity) or 1 Na+ (low affinity) are involved in the uptake of L-tryptophan.

scholarly journals Energetics of renal Na+ and H+/l-alanine co-transport systems

1988 ◽  
Vol 256 (1) ◽  
pp. 299-302 ◽  
Author(s):  
H Jessen ◽  
H Vorum ◽  
K E Jørgensen ◽  
M I Sheikh
Keyword(s):  
Indirect Evidence ◽  
Membrane Vesicles ◽  
Transport Systems ◽  
Rabbit Kidney ◽  
Luminal Membrane ◽  
Alanine Transport ◽  
Pars Recta ◽  
Dependent Transport ◽  
Pars Convoluta ◽  
Convoluted Tubules

The stoichiometric properties of Na+- and H+-dependent L-alanine transporters recently identified in luminal-membrane vesicles prepared from proximal convoluted tubules (pars convoluta) and proximal straight tubules (pars recta) of rabbit kidney were studied. We provide indirect evidence suggesting that one Na+ and one H+ ion are co-transported with the L-alanine molecule via Na+-dependent and H+-dependent transport systems located in vesicles from pars convoluta. Furthermore, our experimental data suggest that both the high-affinity and the low-affinity Na+-dependent L-alanine transport systems of pars recta vesicles operate with a 1:1 stoichiometry.

Segmental localization of the rabbit renal proximal tubular Na+-H+ exchange system

1985 ◽  
Vol 249 (5) ◽  
pp. F704-F712
Author(s):  
U. Kragh-Hansen ◽  
H. Roigaard-Petersen ◽  
M. I. Sheikh
Keyword(s):  
Membrane Vesicles ◽  
Proximal Convoluted Tubule ◽  
Outer Cortex ◽  
Straight Tubule ◽  
Luminal Membrane ◽  
Proximal Straight Tubule ◽  
Pars Recta ◽  
Proximal Tubular ◽  
Renal Proximal Tubular ◽  
Na Uptake

The activity of the Na+-H+ exchanger in rabbit proximal tubule was investigated by using luminal membrane vesicles prepared from "outer cortex" (proximal convoluted tubule) or "outer medulla" (proximal straight tubule). The purity of the preparations was examined by measuring the activity of several marker enzymes, and the degree of cross-contamination and the functional state of the membrane vesicles were assessed by studying Na+-dependent uptake of D-glucose. The Na+ uptake by pars convoluta membrane vesicles exhibited an overshoot in the presence of an intravesicular greater than extravesicular H+ gradient. The overshoot was eliminated by omitting or reversing the transmembranal H+ gradient or by adding amiloride. In contrast, Na+ uptake by pars recta membrane vesicles did not show an overshoot and was independent of H+ gradients and of amiloride. However, Na+ uptake by pars recta membrane vesicles pretreated with monensin exhibited an overshoot. This overshoot apparently was amiloride insensitive. The findings propose that the Na+-H+ exchanger is predominantly operative in the proximal convoluted tubule and is either lacking or of minor significance in the proximal straight tubule.

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