The determination of lactate dehydrogenase isoenzymes in normal human muscle and other tissues

TL;DRAbstract

1. A technique has been developed, based on preferential inhibition by urea, for determining the amounts and proportions of the M and H sub-units of lactate dehydrogenase (referred to as LDH-M and LDH-H respectively) in human tissues, including muscle. 2. There was good agreement between the results obtained with urea inhibition and those obtained with starch-gel electrophoresis. 3. With increasing age there was a significant decrease in the total amount of lactate dehydrogenase and the amount of LDH-M in skeletal muscle. This could not be accounted for by the replacement of functioning muscle tissue by fibrous connective tissue. 4. The proportion of LDH-M was less in certain muscles (e.g. soleus and extra-ocular) than in other muscles (e.g. gastrocnemius and rectus abdominis). 5. The proportions of LDH-M and LDH-H did not differ significantly in different superficial limb muscles and were not significantly affected by either age or sex. 6. Specimens of muscle from 86 different individ

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