MEASUREMENT OF GLUTAMINE-SYNTHETASE ACTIVITY IN RAT MUSCLE BY A COLORIMETRIC ASSAY

Citation
R. Minet et al., MEASUREMENT OF GLUTAMINE-SYNTHETASE ACTIVITY IN RAT MUSCLE BY A COLORIMETRIC ASSAY, Clinica chimica acta, 268(1-2), 1997, pp. 121-132
Citations number
27
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Medical Laboratory Technology",Biology
Journal title
ISSN journal
0009-8981
Volume
268
Issue
1-2
Year of publication
1997
Pages
121 - 132
Database
ISI
SICI code
0009-8981(1997)268:1-2<121:MOGAIR>2.0.ZU;2-O
Abstract
Glutamine synthetase catalyses the formation of L-Gln from L-Glu and N H4+. This enzyme also exerts a glutamyl-transferase activity that prod uces gamma-glutamyl-hydroxamate from Gin and hydroxylamine. This gamma -glutamyl-transfer reaction can be used to determine glutamine synthet ase activity by colorimetric assay. This method has never been applied to rat muscle. The aim of this work was to study and optimize the glu tamine synthetase assay conditions in rat muscle. Enzyme activity was linear with time of incubation (30 min at 37 degrees C) and linear wit h enzyme concentration in the incubation medium. The method was specif ic. In addition, this assay correlated well with a radiometric assay ( y = 0.76x + 340, where x and y are the glutamine synthetase activities measured by radiometry and colorimetry respectively; r = 0.94; P = 0. 05). Finally, no glutamine synthetase activity was found in muscles of rats treated with methionine sulfoximine, an inhibitor of glutamine s ynthetase, and activity dramatically rose in muscles from rats treated with dexamethasone, an activator of glutamine synthetase (in extensor digitorum longus: 2717+/-54 nmol/min/g protein in dexamethasone-treat ed rats versus 1228+/-114 nmol/min/g protein in control rats, P < 0.00 01). In conclusion, the method presented here is accurate and reliable for measurement of glutamine synthetase activity in muscles. (C) 1997 Elsevier Science B.V.