Glutamine synthetase induction by glucocorticoids is preserved in
skeletal muscle of aged rats.
Meynial-Denis, Dominique, Michele Mignon, Ahmed Miri, Jerome Imbert,
Eveline Aurousseau, Daniel Taillandier, Didier Attaix, Maurice Arnal,
and Jean Grizard.
Centre de Recherche en Nutrition Humaine de Clermont-Ferrand and
Institut National de la Recherche Agronomique, Unit[acute]e d'Etude
du M[acute]etabolisme Azot[acute]e, 63122 Ceyrat, France
APStracts 3:0179E, 1996.
Glutamine synthetase (GS) is a glucocorticoid-inducible enzyme which
has a key role for glutamine synthesis in muscle. We hypothesized
that the glucocorticoid induction of GS could be altered in aged
rats, because alterations in the responsiveness of some genes to
glucocorticoids were reported in aging. We compared the
glucocorticoid-induced GS in fast-twitch and slow-twitch skeletal
muscles (tibialis anterior and soleus, respectively) and heart from
adult (6-8 months aged) and aged (22 months aged) female rats. All
animals received dexamethasone (DEX) in their drinking water (0.77+/
-0.10 and 0.80+/-0.08 mg/ day per adult and aged rat, respectively)
for five days. DEX caused an increase in both GS activity and GS mRNA
in fast-twitch and slow-twitch skeletal muscles from adult and aged
rats. In contrast, DEX increased GS activity in heart of adult rats,
without any concomitant change in GS mRNA levels. Furthermore, DEX
did not affect GS activity in aged heart. Thus, the responsiveness of
GS to an excess of glucocorticoids is preserved in skeletal muscle,
but not in heart from aged animals.
Received 2 May 1996; accepted in final form 12 August 1996.
APS Manuscript Number E213-6.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 19 September 1996