title: Creatine analogue beta-guanidinopropionic acid alters skeletal muscle AMP deaminase activity.
abstract: Dietary supplementation of the creatine analogue beta-guanidinopropionic acid (beta-GPA) decreases in vitro skeletal muscle AMP deaminase (AMP-D) activity in rats. Downregulation of AMP-D activity was progressive and greater in fast-twitch muscles (70-80%) than in the slow-twitch soleus muscle (approximately 50%). The loss in AMP-D activity had little effect on inosine 5'-monophosphate accumulation in mixed-fiber muscle with intense tetanic contractions. In contrast, inosine 5'-monophosphate 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 buffers decreases in the ATP/ADPfree ratio via deamination, even though AMP-D activity is less. Isoforms of skeletal muscle AMP-D mRNAs in mixed-fiber muscle were not altered by feeding beta-GPA for up to 9 wk. Creatine depletion did not alter total immunoreactivity; however, a redistribution of AMP-D immunoreactivity from primarily an approximately 80-kDa form toward lower apparent molecular mass species (approximately 60 and approximately 56 kDa) was observed. Posttranslational changes in AMP-D appear related to changes in activity.
authors.affiliation: Department of Physiology, State University of New York Health Science Center at Syracuse 13210, USA.
authors.forename: P C
authors.initials: PC
authors.lastname: Tullson
authors.forename: K W
authors.initials: KW
authors.lastname: Rundell
authors.forename: R L
authors.initials: RL
authors.lastname: Sabina
authors.forename: R L
authors.initials: RL
authors.lastname: Terjung
mesh_terms: D000659:AMP Deaminase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D003401:Creatine / Q000031:analogs & derivatives; D003641:Deamination; D004558:Electric Stimulation; D004789:Enzyme Activation; D006146:Guanidines / Q000494:pharmacology*; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000201:enzymology*; D009693:Nucleic Acid Hybridization; D011422:Propionates / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012260:Ribonucleases; D013997:Time Factors
chemical_list: D006146:Guanidines; D011422:Propionates; D012260:Ribonucleases; D000659:AMP Deaminase; D003401:Creatine; C005775:guanidinopropionic acid