Role of different proteolytic pathways in the degradation of muscle
protein from streptozotocin-diabetic rats.
Pepato, Maria Teresa, Renato H. Migliorini, Alfred L. Goldberg, and
Isis C. Kettelhut.
Departments of Biochemistry and Physiology, School of Medicine,
University of Sao Paulo, 14049-900 Ribeirao Preto - S.P., Brazil,
Department of Cell Biology, Harvard Medical School, Boston, MA
02115,, USA
APStracts 3:0075E, 1996.
In vitro rates of overall proteolysis and the activities of four
different proteolytic pathways (lysosomal, Ca2+-dependent, ATP
-dependent and ATP-independent), as well as rates of protein
synthesis, were measured in soleus and extensor digitorum longus
(EDL) muscles from streptozotocin diabetic rats. In the acute phase
(1-3 days) of diabetes, there was an increase in overall proteolysis
which coincided with an increased activity of the Ca2+-dependent
pathway in both soleus and EDL and of the ATP-dependent pathway in
EDL. After longer periods (5-10 days) of diabetes the overall rate of
protein degradation decreased, and reached values similar or even
lower than controls, as a result of a reduction in the activities of
Ca2+-dependent and ATP-dependent pathways. No change was detected at
any time interval in the activity of the intralysosomal proteolytic
system in muscles from diabetic animals. Rates of protein synthesis
were already reduced 24 hours after diabetes induction and decreased
further thereafter. Insulin treatment restored to normal the
activities of the proteolytic pathways and rates of protein
synthesis.
Received 27 September 1995; accepted in final form 21 March 1996.
APS Manuscript Number E475-5.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 16 April 96