Incorporation of 15N-leucine amine into ATP of fast-twitch muscle following stimulation.

During intense contraction conditions, ATP content in fast-twitch muscle rapidly decreases (approx. 50%) by the deamination of AMP to IMP and NH3. During recovery, the ATP content returns to normal by the reamination of IMP from aspartate. We evaluated whether the donor amine may be obtained from branched chain amino acid uptake by perfusing muscle in situ with 1.0 mM [15N]-leucine during a 1 hr recovery. [15N]-enriched adenine nucleotide accounted for 14% to 24% of the IMP reaminated, depending on whether [15N]-leucine was provided only during the recovery period or, in addition, 30 min prior to stimulation. Thus, the uptake of leucine by fast-twitch muscle may provide an important source of amine for adenine nucleotide resynthesis following contractions.