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Am J Physiol Endocrinol Metab 287: E671-E676, 2004; doi:10.1152/ajpendo.00185.2003
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Metabolic pathways implicated in the kinetic impairment of muscle glutamine homeostasis in adult and old glucocorticoid-treated rats

R. Minet-Quinard,1 C. Moinard,2 F. Villie,1 M. P. Vasson,1 and L. Cynober2

1Department of Biochemistry, Molecular Biology and Nutrition, EA 2416 Human Nutrition Research Center Auvergne, Pharmacy School, 63000 Clermont-Ferrand; and 2Laboratory of Nutrition Biology, EA 2498 Pharmacy School, Paris 5 University, 75006 Paris, France

Submitted 24 April 2003 ; accepted in final form 21 May 2004

An impairment of muscle glutamine metabolism in response to dexamethasone (DEX) occurs with aging. To better characterize this alteration, we have investigated muscle glutamine release with regard to muscle glutamine production (net protein breakdown, de novo glutamine synthesis) in adult and old glucocorticoid-treated rats. Male Sprague-Dawley rats (3 or 24 mo old) were divided into seven groups: three groups received 1.5 mg/kg of DEX once a day by intraperitoneal injection for 3, 5, or 7 days; three groups were pair fed to the three treated groups, respectively; and one control group of healthy rats was fed ad libitum. Muscle glutamine synthetase activity increased earlier in old rats (day 3) than in adult rats (day 7), whereas an increase in muscle glutamine release occurred later in old rats (day 5) than in adult DEX-treated rats (day 3). Consequently, muscle glutamine concentration decreased later in old rats (day 5) than in adults (day 3). Finally, net muscle protein breakdown increased only in old DEX-treated rats (day 7). In conclusion, the impairment of muscle glutamine metabolism is due to a combination of an increase in glutamine production and a delayed increase in glutamine release.

glutamine synthetase; glutamine release; protein breakdown


Address for reprint requests and other correspondence: R. Minet-Quinard, Laboratoire de Biochimie, Biologie Moléculaire et Nutrition, Faculté de Pharmacie 28, place Henri-Dunant, B.P 38, 63001 Clermont-Ferrand cedex 1, France (E-mail: Regine.Minet-Quinard{at}u-clermont1.fr)




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[Abstract] [Full Text] [PDF]


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