Needle biopsy for muscle chemistry.

Needle biopsy can readily provide samples of human skeletal muscle for biochemical analysis. Muscle metabolites are measured by enzymic microanalytical techniques and electrolytes by neutron-activation analysis. This paper summarises the methods of analysis, gives the normal ranges for muscle contents of metabolites and electrolytes, and reviews the reported changes in a number of neuromuscular and metabolic disorders. Muscle is a fairly homogeneous tissue in health, but replacement with fat and fibrous tissue in myopathies causes error in analyses unless metabolites are referred to a reliable standard. It is recommended that needle-biopsy samples to be freeze-dried and dissected to remove connective tissue before analysis. Total creatine (phosphorylcreatine+free creatine) total adenosine+inosine nucleotides, and potassium and phosphorus separtely correlated very highly with sample dry weight after dissection, suggesting that these may be used as standards. When assessing whether a given metabolite is present in an abnormal amount, it is probaby advisable to check the content with reference to more than one standard, since one or more of these may be changed in disease.