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Titolo:
Characterization of aldose reductase from the thick ascending limb of henle's loop of rabbit kidney
Autore:
Grunewald, RW; Eckstein, A; Reisse, CH; Muller, GA;
Indirizzi:
Univ Klin Gottingen, Abt Nephrol & Rheumatol, Gottingen, Germany Univ KlinGottingen Gottingen Germany l & Rheumatol, Gottingen, Germany
Titolo Testata:
NEPHRON
fascicolo: 1, volume: 89, anno: 2001,
pagine: 73 - 81
SICI:
0028-2766(200109)89:1<73:COARFT>2.0.ZU;2-H
Fonte:
ISI
Lingua:
ENG
Soggetto:
RENAL INNER MEDULLA; COLLECTING DUCT CELLS; ALDEHYDE REDUCTASE; DIABETIC RATS; SORBITOL METABOLISM; ORGANIC SOLUTES; PURIFICATION; NACL; GENE; IDENTIFICATION;
Keywords:
osmoregulation; aldose reductase; thick ascending limb of Henle's loop;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Clinical Medicine
Life Sciences
Citazioni:
33
Recensione:
Indirizzi per estratti:
Indirizzo: Grunewald, RW Univ Klin Gottingen, Nephrol Abt, Robert Koch Str 40, D-37075 Gottingen, Germany Univ Klin Gottingen Robert Koch Str 40 Gottingen Germany D-37075
Citazione:
R.W. Grunewald et al., "Characterization of aldose reductase from the thick ascending limb of henle's loop of rabbit kidney", NEPHRON, 89(1), 2001, pp. 73-81

Abstract

Background: The organic osmolyte sorbitol plays an important role in the osmoregulation of immortalized epithelial cells of the thick ascending limb of Henle's loop (TALH) of rabbit. The intracellular sorbitol content seems to depend strongly on the extracellular osmolarity. To investigate the nature of the osmotic regulation we characterized the aldose reductase. Methods: We determined aldose reductase activity enzymatically and the content of organic osmolytes by HPLC. Results: The aldose reductase activity correlates with the extracellular tonicity. Elevating the osmolarity of the medium from 300 to 600 mosm/l by addition of NaCl or sucrose resulted in a significant increase of maximal velocity (V-max) of the adapted cells from 8 +/- 1 mu mol/g x min (300 mosm/l) to 322 +/- 28 mu mol/g x min (600 mosm/l, NaCl)or 54 +/- 9 mu mol/g x min (600 mosm/l, sucrose), respectively, while affinity (K-m) remained unchanged. But we found no rise of aldose reductase activity when extracellular urea concentration was elevated. Similar alterations in V-max were observed when the activity of the highly enriched enzyme was determined with glucose as substrate. Elevation of the extracellular osmolarity by NaCl and sucrose strongly induced the expression of aldose reductase protein with an apparent molecular weight of 39 kD. The affinity of glucose is characteristically low with a K-m above 300 mmol/l. Aldose reductase utilizes both NADPH and with lower affinity NADH as coenzymes. In vitro sulfate ions (0.4 mol/l) results in a two-fold activation of the aldose reductase activity whereas sodium (200-400 mmol/l) decreased the activity significantly (22-33%). Potassium and chloride up to 400 mmol/l did not alter the aldose reductase activity in vitro. Conclusions: These results indicate that the aldose reductase of TALH cells of the outer medulla is osmoticallyregulated and has many similarities with aldose reductase in renal inner medulla. Therefore, intracellular sorbitol synthesis seems to be of similar importance in the osmoregulation of TALH cells as in the inner medulla. Copyright (C) 2001 S. Karger AG, Basel.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 25/11/20 alle ore 00:45:19