AJP - Cell Physiology, Vol 258, Issue 2 C258-C265, Copyright © 1990 by American Physiological Society
Adenine nucleotide degradation in slow-twitch red muscle
P. C. Tullson, D. M. Whitlock and R. L. Terjung
Department of Physiology, State University of New York, Syracuse 13210.
The catabolism of adenine nucleotides (AdN) in rat soleus muscle
(predominantly slow twitch) is very different from that in fast-twitch
muscle. AMP deaminase is highly inhibited during brief (3 min) intense (120
tetani/min) in situ stimulation, resulting in little inosine
5'-monophosphate (IMP) accumulation (0.21 mumol/g). Even with ligation of
the femoral artery during the same brief intense contraction conditions
there is surprisingly little increase in IMP (0.37 mumol/g), although AdN
depletion is evident (-1.30 mumol/g). We have tested the hypothesis that
accumulation of purine nucleosides and bases accounts for the AdN depletion
by measuring purine degradation products using high-performance liquid
chromatography. There was no stoichiometric accumulation of purine
degradation products to account for the observed AdN depletion even though
metabolite recovery was essentially quantitative. We hypothesis that under
these conditions AdN are converted to a form different from purine
nucleoside and base degradation products. In contrast to the inhibition of
AMP deamination seen during brief ischemia, slow-twitch muscle depletes a
substantial fraction (28%) of muscle AdN (1.75 mumol/g) that can be
accounted for stoichiometrically as purine degradation products during an
extended 10-min ischemic period of mild (12 tetani/min) contraction
conditions. IMP accumulation (1 mumol/g) is most prominent with inosine,
accounting for 23% (0.4 mumol/g) of the depleted AdN, showing that
slow-twitch red muscle is capable of both AMP deamination and the
subsequent production of purine nucleosides during an extended period of
ischemic contractions. The present results indicate that AdN metabolism in
the soleus muscle is complex, yielding expected degradation products or a
loss of total purines, depending on contraction conditions.(ABSTRACT
TRUNCATED AT 250 WORDS)
