Imp reamination to amp in rat skeletal muscle fiber types. Tullson, Peter C., Peter G. Arabadjis, Kenneth W. Rundell, and Ronald L. Terjung. Department of Physiology, State University of New York, Health Science Center at Syracuse, Syracuse, New York 13210
APStracts 2:0366C, 1995.
IMP reamination in skeletal muscle fiber sections of the rat hindlimb was studied. High IMP concentrations were established during ischemic contractions in each fiber section; 3.1, 2.8 or 0.6 [mu]mol/g in the fast-twitch white (FTW), fast-twitch red (FTR), and slow-twitch red (STR) muscle sections, respectively. Thereafter, blood flow was restored and stimulation was discontinued to allow reamination of IMP. After either 0, 2, 5, 10, 15 or 20 min of recovery, muscle sections were freeze clamped and analyzed for metabolite contents. IMP was nearly fully reaminated after 10 and 20 min of recovery in STR and FTR, respectively. Reamination in FTW was delayed and slower with only 50% of the IMP reaminated after 20 min of recovery. Significant recovery (75%) of phosphocreatine (PCr) occurs in each fiber section, prior to the onset of reamination. Reamination was also evaluated following high-speed treadmill running with or without inhibition of reamination by hadacidin. Running resulted in large accumulations of IMP in both FTW and FTR (3.5 and 1.4 [mu]mol/g, respectively); FTR IMP was higher with hadacidin treat ment. Reamination after running was much greater in FTR vs. FTW and was associated with recover of PCr. After running, the purine degradation products inosine and hypoxanthine were increased in FTW and FTR in normal and hadacidin treated animals. Plasma inosine, hypoxanthine and urate increased after exercise; concentrations continued to increase if reamination was inhibited by hadacidin. These results demonstrate that when muscle IMP is increased, subse quent degradation and loss of purines occurs. Rapid reamination should minimize the quantity of purine lost from muscle and limit the metabolic cost of replenishing purines by the de novo synthesis or salvage pathways. 

Received 20 June 1995; accepted in final form 28 September 1995.
APS Manuscript Number C359-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95