ISSN:
1432-1424
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary Glutamine uptake by rat renal brushborder vesicles occurred via two distinct saturable processes withK m values of 0.145 and 8.5 mM which were stimulated by both ionic and sodium gradients with a pH optimum of 6.8–7.1 Glutamic acid uptake also occurred by a two-component system withK m values of 0.016 and 3.60 mM. Both components were stimulated specifically by a sodium gradient. The lowK m system for glutamic acid had a pH optimum of 7.2–7.4. Glutamine entry at 0.06 mM was inhibited by a variety of amino acids at 3 mM, including dibasic amino acids, glycine, valine, and phenylalanine. Glutamic acid entry at 0.06 mM was inhibited 20–30% by 3 mM phenylalanine, valine, α-aminoisobutyric acid, and glutamine. No metabolic alteration of glutamic acid was observed on incubation with membrane vesicles, but glutamine was significantly hydrolyzed to glutamic acid upon prolonged incubation. Hydrolysis of glutamine was negligible at 15 sec incubation which was employed for measurement of initial rate of entry. These studies provide support for the existence of an uptake system in the brushborder of the renal proximal tubule cell capable of handling the reabsorption of glutamine normally present in glomerular filtrate.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01869043
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