Adaptation of rat skeletal muscle to creatine depletion: AMP deaminase and AMP deamination.
AMP deaminase catalyzes deamination of the AMP formed in contracting muscles to inosine 5'-monophosphate (IMP). Slow-twitch muscle has only approximately 30% as high a level of AMP deaminase activity as fast-twitch muscle in the rat, and rates of IMP formation during intense contractile activity are much lower in slow-twitch muscle. We found that feeding the creatine analogue beta-guanidinopropionic acid (beta-GPA) to rats, which results in creatine depletion, causes a large decrease in muscle AMP deaminase. This adaptation was used to evaluate the role of AMP deaminase activity level in accounting for differences in IMP production in slow-twitch and fast-twitch muscles. beta-GPA feeding for 3 wk lowered AMP deaminase activity in fast-twitch epitrochlearis muscle to a level similar to that found in the normal slow-twitch soleus muscle but had no effect on the magnitude of the increase in IMP in response to intense contractile activity. Despite a similar decrease in ATP in the normal soleus and the epitrochlearis from beta-GPA-fed rats, the increase in IMP was only approximately 30% as great in the soleus in response to intense contractile activity. These results demonstrate that the accumulation of less IMP in slow- compared with fast-twitch skeletal muscle during contractile activity is not due to the lower level of AMP deaminase in slow-twitch muscle.
Ren
J M
JM
Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
Holloszy
J O
JO
D000659:AMP Deaminase / Q000378:metabolism*; D000222:Adaptation, Physiological / Q000502:physiology*; D000249:Adenosine Monophosphate / Q000378:metabolism*; D000818:Animals; D003401:Creatine / Q000378:metabolism*; D003641:Deamination; D004032:Diet; D006146:Guanidines / Q000378:metabolism; D007291:Inosine Monophosphate / Q000378:metabolism; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D009132:Muscles / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D011422:Propionates / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D006146:Guanidines; D011422:Propionates; D007291:Inosine Monophosphate; D000249:Adenosine Monophosphate; D000659:AMP Deaminase; D003401:Creatine; C005775:guanidinopropionic acid