Validation of creatine, glycogen and L-(+)-lactate determination in biopsy samples of bovine Musculus diaphragma

Whereas reliable measurements of diaphragmatic force and electrical activity are now available in calves, evidence that substrate contents in the bovine diaphragm can be accurately measured is still lacking. The purposes of the present study were therefore a) to describe and test the reliability of methods and procedures used for sampling, lyophilisation, extraction and dosage of muscular lactate, glycogen and creatine contents and b) to report the variation in their levels found along the bovine diaphragm and among individuals. The repeatability of the results yielded by a) assaying the extracts, b) processing and assaying the extracts and c) taking samples at different sites in the muscle was assessed. Neither assay, nor processing effects were significant (P < or = 0.05). Substrates were found to be homogeneously distributed within the two muscles studied. Substrate contents expressed per unit of muscle weight or total creatine were neither more or less variable than when expressed per unit of dry matter.