The purpose of this study was to demonstrate the ability of exogenous ASA to penetrate the skeletal muscle membrane and integrate within the muscle metabolome in wild-type (WT) mice ex vivo.
Fast- and slow-type muscle were surgically removed from the left and right limbs of four female mice into an ex vivo muscle contraction measurement system containing physiological solution with 200 nM 13C-ASA. Left limb muscles were contracted using a fatiguing electrical stimulation protocol and right limb muscles were uncontracted. Immediately after the contraction protocol, muscles were snap frozen. Polar metabolomics assessed 13C-ASA label incorporation into metabolites using mass spectrometry.
13C-ASA uptake was more robust into non-contracted muscles than contracted muscles and equivalently in fast- and slow-twitch muscles. Trace 13C label was detected in ATP, ADP, AMP, inosine, and uridine metabolites (uridine diphosphate (UDP) and monophosphate (UMP)). Overall, UDP biosynthesis sequestered 13C-ASA more than ATP, ADP and AMP. UDP supports cellular glucose storage in the form of glycogen, as well as other reactions crucial for tissue building. The 13C label was not detected in 114 other metabolites within the library of knowns.
The data support ASA is bioavailable to muscle and integrates within the muscle metabolome to generate adenosine nucleotides. There is also novel evidence for ASA’s integration into uridine pyrimidines.