Objective: The aim was to clarify the influence of biopsy technique and the effects of temporal delay between sampling and freezing on tissue contents of labile metabolites.
Methods: Cardiac and skeletal muscle concentrations of adenine nucleotides, phosphocreatine, creatine, and glycogen in pigs were determined in endomyocardial and transmural myocardial biopsies and in skeletal muscle biopsies obtained with either endomyocardial bioptome or Tru-cut needle. The influence of the temporal delay between biopsy sampling and freezing was evaluated by keeping the biopsies at room temperature for varying intervals up to 300 s before freezing.
Results: Skeletal muscle showed higher concentrations of creatine compounds and lower contents of ADP and AMP than cardiac muscle, whereas ATP, total adenine nucleotide pool, and glycogen were similar. Lower phosphocreatine contents were found both in endomyocardial biopsies and in skeletal muscle biopsies obtained with bioptome compared to transmural myocardial biopsies and skeletal muscle biopsies obtained with Tru-cut needle, respectively. Other metabolites were unaffected by the biopsy technique. With extended delays between biopsy sampling and freezing, an increase in skeletal muscle phosphocreatine averaging 26% after 5 min was observed. In the heart, a decrease in glycogen content averaging 42% after 5 min was found. These changes were not related to the biopsy procedure and were not observed within the period usually required to freeze biopsies in experimental as well as clinical settings.
Conclusions: There are essential metabolic differences between cardiac and skeletal muscle. Low endomyocardial phosphocreatine levels are influenced by the biopsy technique, compromising the use of endomyocardial biopsies for establishing myocardial phosphocreatine content. Reliable measurements of adenine nucleotides and glycogen can be obtained with endomyocardial biopsies.