Heterogeneity of sodium-dependent D-glucose transport sites along the proximal tubule: evidence from vesicle studies

1982 ◽  
Vol 242 (4) ◽  
pp. F406-F414 ◽  
Author(s):  
R. J. Turner ◽  
A. Moran
Keyword(s):  
Proximal Tubule ◽  
Glucose Transport ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Kinetic Studies ◽  
Transport Systems ◽  
Rabbit Kidney ◽  
Outer Cortex ◽  
Sodium Dependent

The glucose transport properties of brush border membrane vesicles from the outer cortex (early proximal tubule) and outer medulla (late proximal tubule) of rabbit kidney were studied. In the outer cortical preparation the behavior of the sodium-dependent component of D-glucose flux indicated the presence of a low-affinity transport system with Km congruent to 6 mM and Vmax congruent to 10 nmol.min-1.mg protein-1 as measured under zero trans conditions at 40 mM NaCl and 17 degrees C. By contrast, in the outer medullary preparation this component of flux behaved as a high-affinity system with Km congruent to 0.35 mM and Vmax congruent to 4 nmol.min-1.mg protein-1. Differences in transport specificity between the two preparations were also indicated and glucose uptake by the outer cortical vesicles was significantly more sensitive to inhibition by phlorizin. These results suggest the existence of two distinct sodium-dependent D-glucose transport systems in the renal proximal tubule brush border membrane. The kinetic studies presented here were done under zero trans sodium and glucose conditions. The rationale and methodology for carrying out these measurements reliably are discussed in detail.

Age-related changes in sodium-dependent glucose transport in rat small intestine

1986 ◽  
Vol 251 (2) ◽  
pp. G208-G217 ◽  
Author(s):  
H. J. Freeman ◽  
G. A. Quamme
Keyword(s):  
Small Intestine ◽  
Glucose Transport ◽  
Brush Border ◽  
Brush Border Membrane ◽  
High Capacity ◽  
Membrane Vesicles ◽  
Distal Segment ◽  
Brush Border Membrane Vesicles ◽  
Transport Systems ◽  
Sodium Dependent

Brush-border membrane vesicles were purified from jejunoileal segments of rats ranging from 3 to 156 wk. The kinetics of sodium-dependent glucose cotransport were studied under voltage-clamped, zero trans conditions over a wide range of cis-glucose concentrations (0.005-1.5 mM). Initial glucose uptake in brush-border membrane vesicles isolated from the proximal intestinal segment (50 cm from ligament of Treitz) of rats less than 7-8 wk of age demonstrated a distinct curvilinear Hofstee plot consistent with multiple-transport mechanisms. One system possessed an apparent Vmax of 10.6 +/- 0.5 nmol X mg prot-1 X min-1 and Km of 630 +/- 18 microM. The second system was characterized by Vmax of 0.9 +/- 0.1 nmol X mg prot-1 X min-1 and Km of 12 +/- 1 microM. In contrast, the distal segment (50 cm to end of small intestine) possessed only one sodium-dependent glucose carrier system. The apparent Vmax and Km were 1.11 +/- 0.20 nmol X mg protein-1 X min-1 and 49 +/- 7 microM, respectively. Sodium-activation curves in the presence of 0.3 and 0.03 mM glucose were consistent with more than one sodium ion with both systems. In contrast, rats 12-13 wk old and older possessed both sodium-dependent transport systems in the proximal early and distal small intestine. The high-capacity system is more abundant in the proximal than the distal segment. These data suggest that, under these specific conditions, there are two sodium-dependent glucose carriers in the intestine of young rats: one located in the jejunum characterized by high capacity and low affinity, and the second located throughout the jejunoileum characterized by low capacity and high affinity. Furthermore with age there is a development of the low-affinity system in the distal segments so that both systems are found along the length of the jejunum and ileum. Accordingly, serial and parallel heterogeneity of sodium-dependent glucose transport exists along the small intestine.

scholarly journals Renal transport of neutral amino acids. Tubular localization of Na+-dependent phenylalanine- and glucose-transport systems

1984 ◽  
Vol 220 (1) ◽  
pp. 15-24 ◽  
Author(s):  
U Kragh-Hansen ◽  
H Røigaard-Petersen ◽  
C Jacobsen ◽  
M I Sheikh
Keyword(s):  
Glucose Transport ◽  
Transport System ◽  
Membrane Vesicles ◽  
Transport Systems ◽  
Rabbit Kidney ◽  
Outer Cortex ◽  
High Affinity ◽  
Pars Recta ◽  
Pars Convoluta ◽  
Phenylalanine Transport

The transport properties for phenylalanine and glucose in luminal-membrane vesicles from outer cortex (pars convoluta) and outer medulla (pars recta) of rabbit kidney were studied by a spectrophotometric method. Uptake of phenylalanine as well as of glucose by the two types of membrane vesicles was found to be Na+-dependent, electrogenic and stereospecific. Na+-dependent transport of L-phenylalanine by outer-cortical membrane vesicles could be accounted for by one transport system (KA congruent to 1.5 mM). By contrast, in the outer-medullary preparation, L-phenylalanine transport occurred via two transport systems, namely a high-affinity system with K1A congruent to 0.33 mM and a low-affinity system with K2A congruent to 7 mM respectively. Na+-dependent uptake of D-glucose by pars convoluta and pars recta membrane vesicles could be described by single, but different, transport systems, namely a low-affinity system with KA congruent to 3.5 mM and a high-affinity system with KA congruent to 0.30 mM respectively. Attempts to calculate the stoichiometry of the different Na+/D-glucose transport systems by using Hill-type plots revealed that the ratio of the Na+/hexose co-transport probably is 1:1 in the case of pars convoluta and 2:1 in membrane vesicles from pars recta. The Na+/L-phenylalanine stoichiometry of the pars convoluta transporter probably is 1:1. Both the high-affinity and the low-affinity Na+-dependent L-phenylalanine transport system of pars recta membrane vesicles seem to operate with a 1:1 stoichiometry. The physiological importance of the arrangement of low-affinity and high-affinity transport systems along the kidney proximal tubule is discussed.

scholarly journals Distribution and properties of the glycylsarcosine-transport system in rabbit renal proximal tubule. Studies with isolated brush-border-membrane vesicles

1988 ◽  
Vol 249 (1) ◽  
pp. 247-253 ◽  
Author(s):  
Y Miyamoto ◽  
J L Coone ◽  
V Ganapathy ◽  
F H Leibach
Keyword(s):  
Proximal Tubule ◽  
Transport System ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Peptide Transport ◽  
Outer Cortex ◽  
Outer Medulla ◽  
The Difference

The distribution and properties of the peptide-transport system in rabbit renal proximal tubule was examined with glycylsarcosine as the substrate and using brush-border-membrane vesicles derived from pars convoluta (outer cortex) and pars recta (outer medulla). The dipeptide was transported into these vesicles against a concentration gradient in the presence of an inward-directed H+ gradient, demonstrating the presence of a H+-coupled peptide-transport system in outer-cortical as well as outer-medullary brush-border membranes. Even though the transport was electrogenic and was energized by a H+ gradient in both membranes, the system was more active in outer medullary membranes than in outer cortical membranes. Kinetic analysis showed that, although the affinity of the transport system for glycylsarcosine was similar in both membrane preparations, the capacity of the system was significantly greater in outer medulla than in outer cortex. In addition, the pH profiles of the peptide-transport systems in these membrane preparations also showed dissimilarities. The greater dipeptide uptake in one membrane vis-à-vis the other may probably be due to the difference in the affinity of the transport system for H+ and/or the difference in peptide/H+ stoichiometry.

Calcium and renal adaptation to a phosphate load in the thyroparathyroidectomized rat

1986 ◽  
Vol 251 (5) ◽  
pp. F777-F783
Author(s):  
L. Cheng ◽  
C. Dersch ◽  
E. Kraus ◽  
B. Sacktor
Keyword(s):  
Proximal Tubule ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Phosphate Uptake ◽  
Membrane Vesicle ◽  
Membrane Vesicles ◽  
Plasma Calcium ◽  
Uptake System ◽  
Phosphate Reabsorption ◽  
Sodium Dependent

Infusion of phosphate into thyroparathyroidectomized rats on a normal phosphorus diet caused a decrease in net phosphate reabsorption, even though the plasma concentration of phosphate continued to rise. This response was expressed at the level of the proximal tubule brush-border membrane and was coincident with a decrease in sodium-dependent phosphate uptake in membrane vesicles. Kinetic experiments indicated that the increased phosphate load caused a decrease in the Vmax of the membrane uptake system with no change in the apparent Km for phosphate. The infusion of phosphate resulted in a lowered plasma calcium concentration, and it was previously hypothesized that the inhibition of maximal phosphate reabsorption was mediated by the hypocalcemia. When the fall in plasma calcium was prevented by the simultaneous infusions of calcium and phosphate, the reduction in maximal phosphate reabsorption was blunted; however, the phosphate infusion-induced inhibition of brush-border membrane vesicle phosphate uptake was still evident. Thus a major discrepancy was found to the general concept that renal phosphate reabsorption in vivo correlated positively with sodium-dependent phosphate uptake activity in proximal tubule brush-border membrane vesicles. Several possible explanations to account for this anomaly were discussed. It was also found that calcium infusion into saline-infused thyroparathyroidectomized rats slightly increased maximal phosphate reabsorption but did not affect phosphate uptake in the membrane vesicles.

Gentamicin inhibits Na+-dependent d-glucose transport in rabbit kidney brush-border membrane vesicles

1986 ◽  
Vol 858 (1) ◽  
pp. 153-160 ◽  
Author(s):  
Masaru Horio ◽  
Yoshifumi Fukuhara ◽  
Yoshimasa Orita ◽  
Takeshi Nakanishi ◽  
Hajime Nakahama ◽  
...  
Keyword(s):  
Glucose Transport ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Rabbit Kidney
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