Gastrointestinal tract protein synthesis and mrna levels for
proteolytic systems in adult fasted rats.
Samuels, Susan E., Daniel Taillandier, Eveline Aurousseau, Yves
Cherel, Yvon Le Maho, Maurice Arnal, and Didier Attaix.
Centre de Recherche en Nutrition Humaine de Clermont-Ferrand,
Institut National de la Recherche Agronomique, Unit[acute]e d'Etude
du M[acute]etabolisme Azot[acute]e, 63122 Ceyrat; and Centre
d'Ecologie et Physiologie Energ[acute]etiques, Centre National de la
Recherche Scientifique, 67087 Strasbourg Cedex, France
APStracts 3:0071E, 1996.
We studied protein turnover in the gastrointestinal tract of adult
fasted rats since the mechanisms responsible for protein wasting in
these tissues are poorly understood. Protein mass of stomach, small
intestine, and colon decreased by 14-29 and 21-49% after 1 and 5 d of
fasting, respectively. The fractional rate of in vivo protein
synthesis (ks) was 34% lower after 1 and 5 d fasting in the stomach
due to decreased capacity for protein synthesis (Cs). In small
intestine and colon, ks was not different after 1 d, but was 26%
lower on d 5, mainly because of a reduction in Cs. Thus, protein
wasting in the stomach is primarily mediated by decreased protein
synthesis, but not in small intestine and colon during short term
fasting. To determine which proteolytic systems may be activated in
the gut, we measured mRNA levels for critical components of the
lysosomal (cathepsins B and D), Ca2+-activated (m-calpain), and
ubiquitin-dependent (ubiquitin, 14-kDa E2, and C8 and C9 proteasome
subunits) proteolytic pathways. mRNA levels for most of these
components increased during fasting, suggesting that a coordinated
activation of multiple proteolytic systems contributed to intestinal
protein wasting.
Received 6 November 1995; accepted in final form 18 March 1996.
APS Manuscript Number E522-5.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 1 April 96