Purine nucleoside formation in rat skeletal muscle fiber types.
To determine the capacity for purine nucleotide degradation among skeletal muscle fiber types, we established energy-depleted conditions in muscles of the rat hindlimb by inducing muscle contraction during ischemia. After 5, 10, 15, or 20 min of ischemic contractions, representative muscle sections were freeze-clamped and analyzed for purine nucleotides, nucleosides, and bases. Fast-twitch muscle sections accumulated about fourfold more IMP than the slow-twitch red soleus muscle. Inosine begins to accumulate at < 0.5 mumol/g IMP in slow-twitch muscle and at approximately 2 mumol/g IMP in fast-twitch muscle. This suggests that inosine is formed intracellularly by 5'-nucleotidase acting on IMP and that the activity and/or substrate affinity of the 5'-nucleotidase present in slow-twitch muscle may be higher than in fast-twitch muscle. At similar concentrations of precursor IMP, slow-twitch muscle has a greater capacity for purine nucleoside formation and should be more dependent on salvage and de novo synthesis of purine for the maintenance of muscle adenine nucleotides. Fast-twitch muscles are better able to retain IMP for subsequent reamination due to their lower capacity to degrade IMP to inosine.
Arabadjis
P G
PG
Department of Physiology, State University of New York, Syracuse 13210.
Tullson
P C
PC
Terjung
R L
RL
D000227:Adenine Nucleotides / Q000378:metabolism*; D000241:Adenosine / Q000378:metabolism; D000818:Animals; D004558:Electric Stimulation; D007288:Inosine / Q000378:metabolism; D007291:Inosine Monophosphate / Q000378:metabolism; D007511:Ischemia / Q000378:metabolism* / Q000503:physiopathology; D007700:Kinetics; D009119:Muscle Contraction; D009132:Muscles / Q000098:blood supply / Q000378:metabolism* / Q000502:physiology; D011684:Purine Nucleosides / Q000378:metabolism; D011687:Purines / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013979:Tibial Nerve / Q000502:physiology*; D013997:Time Factors
D000227:Adenine Nucleotides; D011684:Purine Nucleosides; D011687:Purines; D007291:Inosine Monophosphate; D007288:Inosine; D000241:Adenosine