Treatment with the creatine analog [beta]-guanidinopropionic acid
alters skeletal muscle amp deaminase activity in vitro and in
vivo.
Tullson, Peter C., Kenneth W. Rundell, Richard L. Sabina, and Ronald
L. Terjung.
Department of Physiology, State University of New York, Health
Science Center at Syracuse, Syracuse, New York 13210, Department of
Biochemistry, Medical College of Wisconsin, 8701 Watertown Plank
Road, Milwaukee, WI 53226
APStracts 2:0267C, 1995.
Dietary supplementation of the creatine analogue, [beta]
-guanidinopropionic acid (b-GPA) decreases in vitro skeletal muscle
AMP deaminase (AMP-D) activity in rats. Down- regulation of AMP-D
activity was progressive and greater in fast-twitch muscles (70-80%)
than in the slow-twitch soleus muscle (50%). The loss in AMP-D
activity had little effect on IMP accumulation in mixed-fibered
muscle with intense tetanic contractions. In contrast, IMP formation
was evident earlier in fast-twitch red and white fiber sections of
creatine depleted animals during intense twitch contractions
indicating that fast-twitch muscle of [beta]-GPA treated rats buffer
decreases in the ATP/ADPfree ratio via deamination even though AMP-D
activity is less. Isoforms of skeletal muscle AMP-D mRNAs in mixed
-fibered muscle were not altered by feeding [beta]-GPA for up to 9
weeks. Creatine depletion did no alter total immunoreactivity;
however a re-distribution of AMP-D immunoreactivity from primarily an
80 kD form toward lower apparent molecular weights species (60 and 56
kD) was observed. Post-translational changes in AMP-D appear related
to changes in activity.
Received 22 November 1994; accepted in final form 10 July 1995.
APS Manuscript Number C687-4.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 July 1995.